xref: /illumos-gate/usr/src/uts/common/syscall/lwp_sobj.c (revision 2570281cf351044b6936651ce26dbe1f801dcbd8)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 
22 /*
23  * Copyright 2010 Sun Microsystems, Inc.  All rights reserved.
24  * Use is subject to license terms.
25  * Copyright 2015 Joyent, Inc.
26  */
27 
28 /*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T	*/
29 /*	  All Rights Reserved	*/
30 
31 #include <sys/param.h>
32 #include <sys/types.h>
33 #include <sys/sysmacros.h>
34 #include <sys/systm.h>
35 #include <sys/cred.h>
36 #include <sys/user.h>
37 #include <sys/errno.h>
38 #include <sys/file.h>
39 #include <sys/proc.h>
40 #include <sys/prsystm.h>
41 #include <sys/kmem.h>
42 #include <sys/sobject.h>
43 #include <sys/fault.h>
44 #include <sys/procfs.h>
45 #include <sys/watchpoint.h>
46 #include <sys/time.h>
47 #include <sys/cmn_err.h>
48 #include <sys/machlock.h>
49 #include <sys/debug.h>
50 #include <sys/synch.h>
51 #include <sys/synch32.h>
52 #include <sys/mman.h>
53 #include <sys/class.h>
54 #include <sys/schedctl.h>
55 #include <sys/sleepq.h>
56 #include <sys/policy.h>
57 #include <sys/lwpchan_impl.h>
58 #include <sys/turnstile.h>
59 #include <sys/atomic.h>
60 #include <sys/lwp_timer_impl.h>
61 #include <sys/lwp_upimutex_impl.h>
62 #include <vm/as.h>
63 #include <sys/sdt.h>
64 
65 static kthread_t *lwpsobj_owner(caddr_t);
66 static void lwp_unsleep(kthread_t *t);
67 static void lwp_change_pri(kthread_t *t, pri_t pri, pri_t *t_prip);
68 static void lwp_mutex_cleanup(lwpchan_entry_t *ent, uint16_t lockflg);
69 static void lwp_mutex_unregister(void *uaddr);
70 static void set_owner_pid(lwp_mutex_t *, uintptr_t, pid_t);
71 static int iswanted(kthread_t *, lwpchan_t *);
72 
73 extern int lwp_cond_signal(lwp_cond_t *cv);
74 
75 /*
76  * Maximum number of user prio inheritance locks that can be held by a thread.
77  * Used to limit kmem for each thread. This is a per-thread limit that
78  * can be administered on a system wide basis (using /etc/system).
79  *
80  * Also, when a limit, say maxlwps is added for numbers of lwps within a
81  * process, the per-thread limit automatically becomes a process-wide limit
82  * of maximum number of held upi locks within a process:
83  *      maxheldupimx = maxnestupimx * maxlwps;
84  */
85 static uint32_t maxnestupimx = 2000;
86 
87 /*
88  * The sobj_ops vector exports a set of functions needed when a thread
89  * is asleep on a synchronization object of this type.
90  */
91 static sobj_ops_t lwp_sobj_ops = {
92 	SOBJ_USER, lwpsobj_owner, lwp_unsleep, lwp_change_pri
93 };
94 
95 static kthread_t *lwpsobj_pi_owner(upimutex_t *up);
96 
97 static sobj_ops_t lwp_sobj_pi_ops = {
98 	SOBJ_USER_PI, lwpsobj_pi_owner, turnstile_unsleep,
99 	turnstile_change_pri
100 };
101 
102 static sleepq_head_t	lwpsleepq[NSLEEPQ];
103 upib_t			upimutextab[UPIMUTEX_TABSIZE];
104 
105 #define	LWPCHAN_LOCK_SHIFT	10	/* 1024 locks for each pool */
106 #define	LWPCHAN_LOCK_SIZE	(1 << LWPCHAN_LOCK_SHIFT)
107 
108 /*
109  * We know that both lc_wchan and lc_wchan0 are addresses that most
110  * likely are 8-byte aligned, so we shift off the low-order 3 bits.
111  * 'pool' is either 0 or 1.
112  */
113 #define	LWPCHAN_LOCK_HASH(X, pool) \
114 	(((((X) >> 3) ^ ((X) >> (LWPCHAN_LOCK_SHIFT + 3))) & \
115 	(LWPCHAN_LOCK_SIZE - 1)) + ((pool)? LWPCHAN_LOCK_SIZE : 0))
116 
117 static kmutex_t		lwpchanlock[2 * LWPCHAN_LOCK_SIZE];
118 
119 /*
120  * Is this a POSIX threads user-level lock requiring priority inheritance?
121  */
122 #define	UPIMUTEX(type)	((type) & LOCK_PRIO_INHERIT)
123 
124 static sleepq_head_t *
lwpsqhash(lwpchan_t * lwpchan)125 lwpsqhash(lwpchan_t *lwpchan)
126 {
127 	uint_t x = (uintptr_t)lwpchan->lc_wchan ^ (uintptr_t)lwpchan->lc_wchan0;
128 	return (&lwpsleepq[SQHASHINDEX(x)]);
129 }
130 
131 /*
132  * Lock an lwpchan.
133  * Keep this in sync with lwpchan_unlock(), below.
134  */
135 static void
lwpchan_lock(lwpchan_t * lwpchan,int pool)136 lwpchan_lock(lwpchan_t *lwpchan, int pool)
137 {
138 	uint_t x = (uintptr_t)lwpchan->lc_wchan ^ (uintptr_t)lwpchan->lc_wchan0;
139 	mutex_enter(&lwpchanlock[LWPCHAN_LOCK_HASH(x, pool)]);
140 }
141 
142 /*
143  * Unlock an lwpchan.
144  * Keep this in sync with lwpchan_lock(), above.
145  */
146 static void
lwpchan_unlock(lwpchan_t * lwpchan,int pool)147 lwpchan_unlock(lwpchan_t *lwpchan, int pool)
148 {
149 	uint_t x = (uintptr_t)lwpchan->lc_wchan ^ (uintptr_t)lwpchan->lc_wchan0;
150 	mutex_exit(&lwpchanlock[LWPCHAN_LOCK_HASH(x, pool)]);
151 }
152 
153 /*
154  * Delete mappings from the lwpchan cache for pages that are being
155  * unmapped by as_unmap().  Given a range of addresses, "start" to "end",
156  * all mappings within the range are deleted from the lwpchan cache.
157  */
158 void
lwpchan_delete_mapping(proc_t * p,caddr_t start,caddr_t end)159 lwpchan_delete_mapping(proc_t *p, caddr_t start, caddr_t end)
160 {
161 	lwpchan_data_t *lcp;
162 	lwpchan_hashbucket_t *hashbucket;
163 	lwpchan_hashbucket_t *endbucket;
164 	lwpchan_entry_t *ent;
165 	lwpchan_entry_t **prev;
166 	caddr_t addr;
167 
168 	mutex_enter(&p->p_lcp_lock);
169 	lcp = p->p_lcp;
170 	hashbucket = lcp->lwpchan_cache;
171 	endbucket = hashbucket + lcp->lwpchan_size;
172 	for (; hashbucket < endbucket; hashbucket++) {
173 		if (hashbucket->lwpchan_chain == NULL)
174 			continue;
175 		mutex_enter(&hashbucket->lwpchan_lock);
176 		prev = &hashbucket->lwpchan_chain;
177 		/* check entire chain */
178 		while ((ent = *prev) != NULL) {
179 			addr = ent->lwpchan_addr;
180 			if (start <= addr && addr < end) {
181 				*prev = ent->lwpchan_next;
182 				/*
183 				 * We do this only for the obsolete type
184 				 * USYNC_PROCESS_ROBUST.  Otherwise robust
185 				 * locks do not draw ELOCKUNMAPPED or
186 				 * EOWNERDEAD due to being unmapped.
187 				 */
188 				if (ent->lwpchan_pool == LWPCHAN_MPPOOL &&
189 				    (ent->lwpchan_type & USYNC_PROCESS_ROBUST))
190 					lwp_mutex_cleanup(ent, LOCK_UNMAPPED);
191 				/*
192 				 * If there is a user-level robust lock
193 				 * registration, mark it as invalid.
194 				 */
195 				if ((addr = ent->lwpchan_uaddr) != NULL)
196 					lwp_mutex_unregister(addr);
197 				kmem_free(ent, sizeof (*ent));
198 				atomic_dec_32(&lcp->lwpchan_entries);
199 			} else {
200 				prev = &ent->lwpchan_next;
201 			}
202 		}
203 		mutex_exit(&hashbucket->lwpchan_lock);
204 	}
205 	mutex_exit(&p->p_lcp_lock);
206 }
207 
208 /*
209  * Given an lwpchan cache pointer and a process virtual address,
210  * return a pointer to the corresponding lwpchan hash bucket.
211  */
212 static lwpchan_hashbucket_t *
lwpchan_bucket(lwpchan_data_t * lcp,uintptr_t addr)213 lwpchan_bucket(lwpchan_data_t *lcp, uintptr_t addr)
214 {
215 	uint_t i;
216 
217 	/*
218 	 * All user-level sync object addresses are 8-byte aligned.
219 	 * Ignore the lowest 3 bits of the address and use the
220 	 * higher-order 2*lwpchan_bits bits for the hash index.
221 	 */
222 	addr >>= 3;
223 	i = (addr ^ (addr >> lcp->lwpchan_bits)) & lcp->lwpchan_mask;
224 	return (lcp->lwpchan_cache + i);
225 }
226 
227 /*
228  * (Re)allocate the per-process lwpchan cache.
229  */
230 static void
lwpchan_alloc_cache(proc_t * p,uint_t bits)231 lwpchan_alloc_cache(proc_t *p, uint_t bits)
232 {
233 	lwpchan_data_t *lcp;
234 	lwpchan_data_t *old_lcp;
235 	lwpchan_hashbucket_t *hashbucket;
236 	lwpchan_hashbucket_t *endbucket;
237 	lwpchan_hashbucket_t *newbucket;
238 	lwpchan_entry_t *ent;
239 	lwpchan_entry_t *next;
240 	uint_t count;
241 
242 	ASSERT(bits >= LWPCHAN_INITIAL_BITS && bits <= LWPCHAN_MAX_BITS);
243 
244 	lcp = kmem_alloc(sizeof (lwpchan_data_t), KM_SLEEP);
245 	lcp->lwpchan_bits = bits;
246 	lcp->lwpchan_size = 1 << lcp->lwpchan_bits;
247 	lcp->lwpchan_mask = lcp->lwpchan_size - 1;
248 	lcp->lwpchan_entries = 0;
249 	lcp->lwpchan_cache = kmem_zalloc(lcp->lwpchan_size *
250 	    sizeof (lwpchan_hashbucket_t), KM_SLEEP);
251 	lcp->lwpchan_next_data = NULL;
252 
253 	mutex_enter(&p->p_lcp_lock);
254 	if ((old_lcp = p->p_lcp) != NULL) {
255 		if (old_lcp->lwpchan_bits >= bits) {
256 			/* someone beat us to it */
257 			mutex_exit(&p->p_lcp_lock);
258 			kmem_free(lcp->lwpchan_cache, lcp->lwpchan_size *
259 			    sizeof (lwpchan_hashbucket_t));
260 			kmem_free(lcp, sizeof (lwpchan_data_t));
261 			return;
262 		}
263 		/*
264 		 * Acquire all of the old hash table locks.
265 		 */
266 		hashbucket = old_lcp->lwpchan_cache;
267 		endbucket = hashbucket + old_lcp->lwpchan_size;
268 		for (; hashbucket < endbucket; hashbucket++)
269 			mutex_enter(&hashbucket->lwpchan_lock);
270 		/*
271 		 * Move all of the old hash table entries to the
272 		 * new hash table.  The new hash table has not yet
273 		 * been installed so we don't need any of its locks.
274 		 */
275 		count = 0;
276 		hashbucket = old_lcp->lwpchan_cache;
277 		for (; hashbucket < endbucket; hashbucket++) {
278 			ent = hashbucket->lwpchan_chain;
279 			while (ent != NULL) {
280 				next = ent->lwpchan_next;
281 				newbucket = lwpchan_bucket(lcp,
282 				    (uintptr_t)ent->lwpchan_addr);
283 				ent->lwpchan_next = newbucket->lwpchan_chain;
284 				newbucket->lwpchan_chain = ent;
285 				ent = next;
286 				count++;
287 			}
288 			hashbucket->lwpchan_chain = NULL;
289 		}
290 		lcp->lwpchan_entries = count;
291 	}
292 
293 	/*
294 	 * Retire the old hash table.  We can't actually kmem_free() it
295 	 * now because someone may still have a pointer to it.  Instead,
296 	 * we link it onto the new hash table's list of retired hash tables.
297 	 * The new hash table is double the size of the previous one, so
298 	 * the total size of all retired hash tables is less than the size
299 	 * of the new one.  exit() and exec() free the retired hash tables
300 	 * (see lwpchan_destroy_cache(), below).
301 	 */
302 	lcp->lwpchan_next_data = old_lcp;
303 
304 	/*
305 	 * As soon as we store the new lcp, future locking operations will
306 	 * use it.  Therefore, we must ensure that all the state we've just
307 	 * established reaches global visibility before the new lcp does.
308 	 */
309 	membar_producer();
310 	p->p_lcp = lcp;
311 
312 	if (old_lcp != NULL) {
313 		/*
314 		 * Release all of the old hash table locks.
315 		 */
316 		hashbucket = old_lcp->lwpchan_cache;
317 		for (; hashbucket < endbucket; hashbucket++)
318 			mutex_exit(&hashbucket->lwpchan_lock);
319 	}
320 	mutex_exit(&p->p_lcp_lock);
321 }
322 
323 /*
324  * Deallocate the lwpchan cache, and any dynamically allocated mappings.
325  * Called when the process exits or execs.  All lwps except one have
326  * exited so we need no locks here.
327  */
328 void
lwpchan_destroy_cache(int exec)329 lwpchan_destroy_cache(int exec)
330 {
331 	proc_t *p = curproc;
332 	lwpchan_hashbucket_t *hashbucket;
333 	lwpchan_hashbucket_t *endbucket;
334 	lwpchan_data_t *lcp;
335 	lwpchan_entry_t *ent;
336 	lwpchan_entry_t *next;
337 	uint16_t lockflg;
338 
339 	lcp = p->p_lcp;
340 	p->p_lcp = NULL;
341 
342 	lockflg = exec? LOCK_UNMAPPED : LOCK_OWNERDEAD;
343 	hashbucket = lcp->lwpchan_cache;
344 	endbucket = hashbucket + lcp->lwpchan_size;
345 	for (; hashbucket < endbucket; hashbucket++) {
346 		ent = hashbucket->lwpchan_chain;
347 		hashbucket->lwpchan_chain = NULL;
348 		while (ent != NULL) {
349 			next = ent->lwpchan_next;
350 			if (ent->lwpchan_pool == LWPCHAN_MPPOOL &&
351 			    (ent->lwpchan_type & (USYNC_PROCESS | LOCK_ROBUST))
352 			    == (USYNC_PROCESS | LOCK_ROBUST))
353 				lwp_mutex_cleanup(ent, lockflg);
354 			kmem_free(ent, sizeof (*ent));
355 			ent = next;
356 		}
357 	}
358 
359 	while (lcp != NULL) {
360 		lwpchan_data_t *next_lcp = lcp->lwpchan_next_data;
361 		kmem_free(lcp->lwpchan_cache, lcp->lwpchan_size *
362 		    sizeof (lwpchan_hashbucket_t));
363 		kmem_free(lcp, sizeof (lwpchan_data_t));
364 		lcp = next_lcp;
365 	}
366 }
367 
368 /*
369  * Return zero when there is an entry in the lwpchan cache for the
370  * given process virtual address and non-zero when there is not.
371  * The returned non-zero value is the current length of the
372  * hash chain plus one.  The caller holds the hash bucket lock.
373  */
374 static uint_t
lwpchan_cache_mapping(caddr_t addr,int type,int pool,lwpchan_t * lwpchan,lwpchan_hashbucket_t * hashbucket)375 lwpchan_cache_mapping(caddr_t addr, int type, int pool, lwpchan_t *lwpchan,
376 	lwpchan_hashbucket_t *hashbucket)
377 {
378 	lwpchan_entry_t *ent;
379 	uint_t count = 1;
380 
381 	for (ent = hashbucket->lwpchan_chain; ent; ent = ent->lwpchan_next) {
382 		if (ent->lwpchan_addr == addr) {
383 			if (ent->lwpchan_type != type ||
384 			    ent->lwpchan_pool != pool) {
385 				/*
386 				 * This shouldn't happen, but might if the
387 				 * process reuses its memory for different
388 				 * types of sync objects.  We test first
389 				 * to avoid grabbing the memory cache line.
390 				 */
391 				ent->lwpchan_type = (uint16_t)type;
392 				ent->lwpchan_pool = (uint16_t)pool;
393 			}
394 			*lwpchan = ent->lwpchan_lwpchan;
395 			return (0);
396 		}
397 		count++;
398 	}
399 	return (count);
400 }
401 
402 /*
403  * Return the cached lwpchan mapping if cached, otherwise insert
404  * a virtual address to lwpchan mapping into the cache.
405  */
406 static int
lwpchan_get_mapping(struct as * as,caddr_t addr,caddr_t uaddr,int type,lwpchan_t * lwpchan,int pool)407 lwpchan_get_mapping(struct as *as, caddr_t addr, caddr_t uaddr,
408 	int type, lwpchan_t *lwpchan, int pool)
409 {
410 	proc_t *p = curproc;
411 	lwpchan_data_t *lcp;
412 	lwpchan_hashbucket_t *hashbucket;
413 	lwpchan_entry_t *ent;
414 	memid_t	memid;
415 	uint_t count;
416 	uint_t bits;
417 
418 top:
419 	/* initialize the lwpchan cache, if necesary */
420 	if ((lcp = p->p_lcp) == NULL) {
421 		lwpchan_alloc_cache(p, LWPCHAN_INITIAL_BITS);
422 		goto top;
423 	}
424 	hashbucket = lwpchan_bucket(lcp, (uintptr_t)addr);
425 	mutex_enter(&hashbucket->lwpchan_lock);
426 	if (lcp != p->p_lcp) {
427 		/* someone resized the lwpchan cache; start over */
428 		mutex_exit(&hashbucket->lwpchan_lock);
429 		goto top;
430 	}
431 	if (lwpchan_cache_mapping(addr, type, pool, lwpchan, hashbucket) == 0) {
432 		/* it's in the cache */
433 		mutex_exit(&hashbucket->lwpchan_lock);
434 		return (1);
435 	}
436 	mutex_exit(&hashbucket->lwpchan_lock);
437 	if (as_getmemid(as, addr, &memid) != 0)
438 		return (0);
439 	lwpchan->lc_wchan0 = (caddr_t)(uintptr_t)memid.val[0];
440 	lwpchan->lc_wchan = (caddr_t)(uintptr_t)memid.val[1];
441 	ent = kmem_alloc(sizeof (lwpchan_entry_t), KM_SLEEP);
442 	mutex_enter(&hashbucket->lwpchan_lock);
443 	if (lcp != p->p_lcp) {
444 		/* someone resized the lwpchan cache; start over */
445 		mutex_exit(&hashbucket->lwpchan_lock);
446 		kmem_free(ent, sizeof (*ent));
447 		goto top;
448 	}
449 	count = lwpchan_cache_mapping(addr, type, pool, lwpchan, hashbucket);
450 	if (count == 0) {
451 		/* someone else added this entry to the cache */
452 		mutex_exit(&hashbucket->lwpchan_lock);
453 		kmem_free(ent, sizeof (*ent));
454 		return (1);
455 	}
456 	if (count > lcp->lwpchan_bits + 2 && /* larger table, longer chains */
457 	    (bits = lcp->lwpchan_bits) < LWPCHAN_MAX_BITS) {
458 		/* hash chain too long; reallocate the hash table */
459 		mutex_exit(&hashbucket->lwpchan_lock);
460 		kmem_free(ent, sizeof (*ent));
461 		lwpchan_alloc_cache(p, bits + 1);
462 		goto top;
463 	}
464 	ent->lwpchan_addr = addr;
465 	ent->lwpchan_uaddr = uaddr;
466 	ent->lwpchan_type = (uint16_t)type;
467 	ent->lwpchan_pool = (uint16_t)pool;
468 	ent->lwpchan_lwpchan = *lwpchan;
469 	ent->lwpchan_next = hashbucket->lwpchan_chain;
470 	hashbucket->lwpchan_chain = ent;
471 	atomic_inc_32(&lcp->lwpchan_entries);
472 	mutex_exit(&hashbucket->lwpchan_lock);
473 	return (1);
474 }
475 
476 /*
477  * Return a unique pair of identifiers that corresponds to a
478  * synchronization object's virtual address.  Process-shared
479  * sync objects usually get vnode/offset from as_getmemid().
480  */
481 static int
get_lwpchan(struct as * as,caddr_t addr,int type,lwpchan_t * lwpchan,int pool)482 get_lwpchan(struct as *as, caddr_t addr, int type, lwpchan_t *lwpchan, int pool)
483 {
484 	/*
485 	 * If the lwp synch object is defined to be process-private,
486 	 * we just make the first field of the lwpchan be 'as' and
487 	 * the second field be the synch object's virtual address.
488 	 * (segvn_getmemid() does the same for MAP_PRIVATE mappings.)
489 	 * The lwpchan cache is used only for process-shared objects.
490 	 */
491 	if (!(type & USYNC_PROCESS)) {
492 		lwpchan->lc_wchan0 = (caddr_t)as;
493 		lwpchan->lc_wchan = addr;
494 		return (1);
495 	}
496 
497 	return (lwpchan_get_mapping(as, addr, NULL, type, lwpchan, pool));
498 }
499 
500 static void
lwp_block(lwpchan_t * lwpchan)501 lwp_block(lwpchan_t *lwpchan)
502 {
503 	kthread_t *t = curthread;
504 	klwp_t *lwp = ttolwp(t);
505 	sleepq_head_t *sqh;
506 
507 	thread_lock(t);
508 	t->t_flag |= T_WAKEABLE;
509 	t->t_lwpchan = *lwpchan;
510 	t->t_sobj_ops = &lwp_sobj_ops;
511 	t->t_release = 0;
512 	sqh = lwpsqhash(lwpchan);
513 	disp_lock_enter_high(&sqh->sq_lock);
514 	CL_SLEEP(t);
515 	DTRACE_SCHED(sleep);
516 	THREAD_SLEEP(t, &sqh->sq_lock);
517 	sleepq_insert(&sqh->sq_queue, t);
518 	thread_unlock(t);
519 	lwp->lwp_asleep = 1;
520 	lwp->lwp_sysabort = 0;
521 	lwp->lwp_ru.nvcsw++;
522 	(void) new_mstate(curthread, LMS_SLEEP);
523 }
524 
525 static kthread_t *
lwpsobj_pi_owner(upimutex_t * up)526 lwpsobj_pi_owner(upimutex_t *up)
527 {
528 	return (up->upi_owner);
529 }
530 
531 static struct upimutex *
upi_get(upib_t * upibp,lwpchan_t * lcp)532 upi_get(upib_t *upibp, lwpchan_t *lcp)
533 {
534 	struct upimutex *upip;
535 
536 	for (upip = upibp->upib_first; upip != NULL;
537 	    upip = upip->upi_nextchain) {
538 		if (upip->upi_lwpchan.lc_wchan0 == lcp->lc_wchan0 &&
539 		    upip->upi_lwpchan.lc_wchan == lcp->lc_wchan)
540 			break;
541 	}
542 	return (upip);
543 }
544 
545 static void
upi_chain_add(upib_t * upibp,struct upimutex * upimutex)546 upi_chain_add(upib_t *upibp, struct upimutex *upimutex)
547 {
548 	ASSERT(MUTEX_HELD(&upibp->upib_lock));
549 
550 	/*
551 	 * Insert upimutex at front of list. Maybe a bit unfair
552 	 * but assume that not many lwpchans hash to the same
553 	 * upimutextab bucket, i.e. the list of upimutexes from
554 	 * upib_first is not too long.
555 	 */
556 	upimutex->upi_nextchain = upibp->upib_first;
557 	upibp->upib_first = upimutex;
558 }
559 
560 static void
upi_chain_del(upib_t * upibp,struct upimutex * upimutex)561 upi_chain_del(upib_t *upibp, struct upimutex *upimutex)
562 {
563 	struct upimutex **prev;
564 
565 	ASSERT(MUTEX_HELD(&upibp->upib_lock));
566 
567 	prev = &upibp->upib_first;
568 	while (*prev != upimutex) {
569 		prev = &(*prev)->upi_nextchain;
570 	}
571 	*prev = upimutex->upi_nextchain;
572 	upimutex->upi_nextchain = NULL;
573 }
574 
575 /*
576  * Add upimutex to chain of upimutexes held by curthread.
577  * Returns number of upimutexes held by curthread.
578  */
579 static uint32_t
upi_mylist_add(struct upimutex * upimutex)580 upi_mylist_add(struct upimutex *upimutex)
581 {
582 	kthread_t *t = curthread;
583 
584 	/*
585 	 * Insert upimutex at front of list of upimutexes owned by t. This
586 	 * would match typical LIFO order in which nested locks are acquired
587 	 * and released.
588 	 */
589 	upimutex->upi_nextowned = t->t_upimutex;
590 	t->t_upimutex = upimutex;
591 	t->t_nupinest++;
592 	ASSERT(t->t_nupinest > 0);
593 	return (t->t_nupinest);
594 }
595 
596 /*
597  * Delete upimutex from list of upimutexes owned by curthread.
598  */
599 static void
upi_mylist_del(struct upimutex * upimutex)600 upi_mylist_del(struct upimutex *upimutex)
601 {
602 	kthread_t *t = curthread;
603 	struct upimutex **prev;
604 
605 	/*
606 	 * Since the order in which nested locks are acquired and released,
607 	 * is typically LIFO, and typical nesting levels are not too deep, the
608 	 * following should not be expensive in the general case.
609 	 */
610 	prev = &t->t_upimutex;
611 	while (*prev != upimutex) {
612 		prev = &(*prev)->upi_nextowned;
613 	}
614 	*prev = upimutex->upi_nextowned;
615 	upimutex->upi_nextowned = NULL;
616 	ASSERT(t->t_nupinest > 0);
617 	t->t_nupinest--;
618 }
619 
620 /*
621  * Returns true if upimutex is owned. Should be called only when upim points
622  * to kmem which cannot disappear from underneath.
623  */
624 static int
upi_owned(upimutex_t * upim)625 upi_owned(upimutex_t *upim)
626 {
627 	return (upim->upi_owner == curthread);
628 }
629 
630 /*
631  * Returns pointer to kernel object (upimutex_t *) if lp is owned.
632  */
633 static struct upimutex *
lwp_upimutex_owned(lwp_mutex_t * lp,uint8_t type)634 lwp_upimutex_owned(lwp_mutex_t *lp, uint8_t type)
635 {
636 	lwpchan_t lwpchan;
637 	upib_t *upibp;
638 	struct upimutex *upimutex;
639 
640 	if (!get_lwpchan(curproc->p_as, (caddr_t)lp, type,
641 	    &lwpchan, LWPCHAN_MPPOOL))
642 		return (NULL);
643 
644 	upibp = &UPI_CHAIN(lwpchan);
645 	mutex_enter(&upibp->upib_lock);
646 	upimutex = upi_get(upibp, &lwpchan);
647 	if (upimutex == NULL || upimutex->upi_owner != curthread) {
648 		mutex_exit(&upibp->upib_lock);
649 		return (NULL);
650 	}
651 	mutex_exit(&upibp->upib_lock);
652 	return (upimutex);
653 }
654 
655 /*
656  * Unlocks upimutex, waking up waiters if any. upimutex kmem is freed if
657  * no lock hand-off occurrs.
658  */
659 static void
upimutex_unlock(struct upimutex * upimutex,uint16_t flag)660 upimutex_unlock(struct upimutex *upimutex, uint16_t flag)
661 {
662 	turnstile_t *ts;
663 	upib_t *upibp;
664 	kthread_t *newowner;
665 
666 	upi_mylist_del(upimutex);
667 	upibp = upimutex->upi_upibp;
668 	mutex_enter(&upibp->upib_lock);
669 	if (upimutex->upi_waiter != 0) { /* if waiters */
670 		ts = turnstile_lookup(upimutex);
671 		if (ts != NULL && !(flag & LOCK_NOTRECOVERABLE)) {
672 			/* hand-off lock to highest prio waiter */
673 			newowner = ts->ts_sleepq[TS_WRITER_Q].sq_first;
674 			upimutex->upi_owner = newowner;
675 			if (ts->ts_waiters == 1)
676 				upimutex->upi_waiter = 0;
677 			turnstile_wakeup(ts, TS_WRITER_Q, 1, newowner);
678 			mutex_exit(&upibp->upib_lock);
679 			return;
680 		} else if (ts != NULL) {
681 			/* LOCK_NOTRECOVERABLE: wakeup all */
682 			turnstile_wakeup(ts, TS_WRITER_Q, ts->ts_waiters, NULL);
683 		} else {
684 			/*
685 			 * Misleading w bit. Waiters might have been
686 			 * interrupted. No need to clear the w bit (upimutex
687 			 * will soon be freed). Re-calculate PI from existing
688 			 * waiters.
689 			 */
690 			turnstile_exit(upimutex);
691 			turnstile_pi_recalc();
692 		}
693 	}
694 	/*
695 	 * no waiters, or LOCK_NOTRECOVERABLE.
696 	 * remove from the bucket chain of upi mutexes.
697 	 * de-allocate kernel memory (upimutex).
698 	 */
699 	upi_chain_del(upimutex->upi_upibp, upimutex);
700 	mutex_exit(&upibp->upib_lock);
701 	kmem_free(upimutex, sizeof (upimutex_t));
702 }
703 
704 static int
lwp_upimutex_lock(lwp_mutex_t * lp,uint8_t type,int try,lwp_timer_t * lwptp)705 lwp_upimutex_lock(lwp_mutex_t *lp, uint8_t type, int try, lwp_timer_t *lwptp)
706 {
707 	label_t ljb;
708 	int error = 0;
709 	lwpchan_t lwpchan;
710 	uint16_t flag;
711 	upib_t *upibp;
712 	volatile struct upimutex *upimutex = NULL;
713 	turnstile_t *ts;
714 	uint32_t nupinest;
715 	volatile int upilocked = 0;
716 
717 	if (on_fault(&ljb)) {
718 		if (upilocked)
719 			upimutex_unlock((upimutex_t *)upimutex, 0);
720 		error = EFAULT;
721 		goto out;
722 	}
723 	if (!get_lwpchan(curproc->p_as, (caddr_t)lp, type,
724 	    &lwpchan, LWPCHAN_MPPOOL)) {
725 		error = EFAULT;
726 		goto out;
727 	}
728 	upibp = &UPI_CHAIN(lwpchan);
729 retry:
730 	mutex_enter(&upibp->upib_lock);
731 	upimutex = upi_get(upibp, &lwpchan);
732 	if (upimutex == NULL)  {
733 		/* lock available since lwpchan has no upimutex */
734 		upimutex = kmem_zalloc(sizeof (upimutex_t), KM_SLEEP);
735 		upi_chain_add(upibp, (upimutex_t *)upimutex);
736 		upimutex->upi_owner = curthread; /* grab lock */
737 		upimutex->upi_upibp = upibp;
738 		upimutex->upi_vaddr = lp;
739 		upimutex->upi_lwpchan = lwpchan;
740 		mutex_exit(&upibp->upib_lock);
741 		nupinest = upi_mylist_add((upimutex_t *)upimutex);
742 		upilocked = 1;
743 		fuword16_noerr(&lp->mutex_flag, &flag);
744 		if (nupinest > maxnestupimx &&
745 		    secpolicy_resource(CRED()) != 0) {
746 			upimutex_unlock((upimutex_t *)upimutex, flag);
747 			error = ENOMEM;
748 			goto out;
749 		}
750 		if (flag & LOCK_NOTRECOVERABLE) {
751 			/*
752 			 * Since the setting of LOCK_NOTRECOVERABLE
753 			 * was done under the high-level upi mutex,
754 			 * in lwp_upimutex_unlock(), this flag needs to
755 			 * be checked while holding the upi mutex.
756 			 * If set, this thread should return without
757 			 * the lock held, and with the right error code.
758 			 */
759 			upimutex_unlock((upimutex_t *)upimutex, flag);
760 			upilocked = 0;
761 			error = ENOTRECOVERABLE;
762 		} else if (flag & (LOCK_OWNERDEAD | LOCK_UNMAPPED)) {
763 			if (flag & LOCK_OWNERDEAD)
764 				error = EOWNERDEAD;
765 			else if (type & USYNC_PROCESS_ROBUST)
766 				error = ELOCKUNMAPPED;
767 			else
768 				error = EOWNERDEAD;
769 		}
770 		goto out;
771 	}
772 	/*
773 	 * If a upimutex object exists, it must have an owner.
774 	 * This is due to lock hand-off, and release of upimutex when no
775 	 * waiters are present at unlock time,
776 	 */
777 	ASSERT(upimutex->upi_owner != NULL);
778 	if (upimutex->upi_owner == curthread) {
779 		/*
780 		 * The user wrapper can check if the mutex type is
781 		 * ERRORCHECK: if not, it should stall at user-level.
782 		 * If so, it should return the error code.
783 		 */
784 		mutex_exit(&upibp->upib_lock);
785 		error = EDEADLK;
786 		goto out;
787 	}
788 	if (try == UPIMUTEX_TRY) {
789 		mutex_exit(&upibp->upib_lock);
790 		error = EBUSY;
791 		goto out;
792 	}
793 	/*
794 	 * Block for the lock.
795 	 */
796 	if ((error = lwptp->lwpt_time_error) != 0) {
797 		/*
798 		 * The SUSV3 Posix spec is very clear that we
799 		 * should get no error from validating the
800 		 * timer until we would actually sleep.
801 		 */
802 		mutex_exit(&upibp->upib_lock);
803 		goto out;
804 	}
805 	if (lwptp->lwpt_tsp != NULL) {
806 		/*
807 		 * Unlike the protocol for other lwp timedwait operations,
808 		 * we must drop t_delay_lock before going to sleep in
809 		 * turnstile_block() for a upi mutex.
810 		 * See the comments below and in turnstile.c
811 		 */
812 		mutex_enter(&curthread->t_delay_lock);
813 		(void) lwp_timer_enqueue(lwptp);
814 		mutex_exit(&curthread->t_delay_lock);
815 	}
816 	/*
817 	 * Now, set the waiter bit and block for the lock in turnstile_block().
818 	 * No need to preserve the previous wbit since a lock try is not
819 	 * attempted after setting the wait bit. Wait bit is set under
820 	 * the upib_lock, which is not released until the turnstile lock
821 	 * is acquired. Say, the upimutex is L:
822 	 *
823 	 * 1. upib_lock is held so the waiter does not have to retry L after
824 	 *    setting the wait bit: since the owner has to grab the upib_lock
825 	 *    to unlock L, it will certainly see the wait bit set.
826 	 * 2. upib_lock is not released until the turnstile lock is acquired.
827 	 *    This is the key to preventing a missed wake-up. Otherwise, the
828 	 *    owner could acquire the upib_lock, and the tc_lock, to call
829 	 *    turnstile_wakeup(). All this, before the waiter gets tc_lock
830 	 *    to sleep in turnstile_block(). turnstile_wakeup() will then not
831 	 *    find this waiter, resulting in the missed wakeup.
832 	 * 3. The upib_lock, being a kernel mutex, cannot be released while
833 	 *    holding the tc_lock (since mutex_exit() could need to acquire
834 	 *    the same tc_lock)...and so is held when calling turnstile_block().
835 	 *    The address of upib_lock is passed to turnstile_block() which
836 	 *    releases it after releasing all turnstile locks, and before going
837 	 *    to sleep in swtch().
838 	 * 4. The waiter value cannot be a count of waiters, because a waiter
839 	 *    can be interrupted. The interrupt occurs under the tc_lock, at
840 	 *    which point, the upib_lock cannot be locked, to decrement waiter
841 	 *    count. So, just treat the waiter state as a bit, not a count.
842 	 */
843 	ts = turnstile_lookup((upimutex_t *)upimutex);
844 	upimutex->upi_waiter = 1;
845 	error = turnstile_block(ts, TS_WRITER_Q, (upimutex_t *)upimutex,
846 	    &lwp_sobj_pi_ops, &upibp->upib_lock, lwptp);
847 	/*
848 	 * Hand-off implies that we wakeup holding the lock, except when:
849 	 *	- deadlock is detected
850 	 *	- lock is not recoverable
851 	 *	- we got an interrupt or timeout
852 	 * If we wake up due to an interrupt or timeout, we may
853 	 * or may not be holding the lock due to mutex hand-off.
854 	 * Use lwp_upimutex_owned() to check if we do hold the lock.
855 	 */
856 	if (error != 0) {
857 		if ((error == EINTR || error == ETIME) &&
858 		    (upimutex = lwp_upimutex_owned(lp, type))) {
859 			/*
860 			 * Unlock and return - the re-startable syscall will
861 			 * try the lock again if we got EINTR.
862 			 */
863 			(void) upi_mylist_add((upimutex_t *)upimutex);
864 			upimutex_unlock((upimutex_t *)upimutex, 0);
865 		}
866 		/*
867 		 * The only other possible error is EDEADLK.  If so, upimutex
868 		 * is valid, since its owner is deadlocked with curthread.
869 		 */
870 		ASSERT(error == EINTR || error == ETIME ||
871 		    (error == EDEADLK && !upi_owned((upimutex_t *)upimutex)));
872 		ASSERT(!lwp_upimutex_owned(lp, type));
873 		goto out;
874 	}
875 	if (lwp_upimutex_owned(lp, type)) {
876 		ASSERT(lwp_upimutex_owned(lp, type) == upimutex);
877 		nupinest = upi_mylist_add((upimutex_t *)upimutex);
878 		upilocked = 1;
879 	}
880 	/*
881 	 * Now, need to read the user-level lp->mutex_flag to do the following:
882 	 *
883 	 * - if lock is held, check if EOWNERDEAD or ELOCKUNMAPPED
884 	 *   should be returned.
885 	 * - if lock isn't held, check if ENOTRECOVERABLE should
886 	 *   be returned.
887 	 *
888 	 * Now, either lp->mutex_flag is readable or it's not. If not
889 	 * readable, the on_fault path will cause a return with EFAULT
890 	 * as it should.  If it is readable, the state of the flag
891 	 * encodes the robustness state of the lock:
892 	 *
893 	 * If the upimutex is locked here, the flag's LOCK_OWNERDEAD
894 	 * or LOCK_UNMAPPED setting will influence the return code
895 	 * appropriately.  If the upimutex is not locked here, this
896 	 * could be due to a spurious wake-up or a NOTRECOVERABLE
897 	 * event.  The flag's setting can be used to distinguish
898 	 * between these two events.
899 	 */
900 	fuword16_noerr(&lp->mutex_flag, &flag);
901 	if (upilocked) {
902 		/*
903 		 * If the thread wakes up from turnstile_block with the lock
904 		 * held, the flag could not be set to LOCK_NOTRECOVERABLE,
905 		 * since it would not have been handed-off the lock.
906 		 * So, no need to check for this case.
907 		 */
908 		if (nupinest > maxnestupimx &&
909 		    secpolicy_resource(CRED()) != 0) {
910 			upimutex_unlock((upimutex_t *)upimutex, flag);
911 			upilocked = 0;
912 			error = ENOMEM;
913 		} else if (flag & (LOCK_OWNERDEAD | LOCK_UNMAPPED)) {
914 			if (flag & LOCK_OWNERDEAD)
915 				error = EOWNERDEAD;
916 			else if (type & USYNC_PROCESS_ROBUST)
917 				error = ELOCKUNMAPPED;
918 			else
919 				error = EOWNERDEAD;
920 		}
921 	} else {
922 		/*
923 		 * Wake-up without the upimutex held. Either this is a
924 		 * spurious wake-up (due to signals, forkall(), whatever), or
925 		 * it is a LOCK_NOTRECOVERABLE robustness event. The setting
926 		 * of the mutex flag can be used to distinguish between the
927 		 * two events.
928 		 */
929 		if (flag & LOCK_NOTRECOVERABLE) {
930 			error = ENOTRECOVERABLE;
931 		} else {
932 			/*
933 			 * Here, the flag could be set to LOCK_OWNERDEAD or
934 			 * not. In both cases, this is a spurious wakeup,
935 			 * since the upi lock is not held, but the thread
936 			 * has returned from turnstile_block().
937 			 *
938 			 * The user flag could be LOCK_OWNERDEAD if, at the
939 			 * same time as curthread having been woken up
940 			 * spuriously, the owner (say Tdead) has died, marked
941 			 * the mutex flag accordingly, and handed off the lock
942 			 * to some other waiter (say Tnew). curthread just
943 			 * happened to read the flag while Tnew has yet to deal
944 			 * with the owner-dead event.
945 			 *
946 			 * In this event, curthread should retry the lock.
947 			 * If Tnew is able to cleanup the lock, curthread
948 			 * will eventually get the lock with a zero error code,
949 			 * If Tnew is unable to cleanup, its eventual call to
950 			 * unlock the lock will result in the mutex flag being
951 			 * set to LOCK_NOTRECOVERABLE, and the wake-up of
952 			 * all waiters, including curthread, which will then
953 			 * eventually return ENOTRECOVERABLE due to the above
954 			 * check.
955 			 *
956 			 * Of course, if the user-flag is not set with
957 			 * LOCK_OWNERDEAD, retrying is the thing to do, since
958 			 * this is definitely a spurious wakeup.
959 			 */
960 			goto retry;
961 		}
962 	}
963 
964 out:
965 	no_fault();
966 	return (error);
967 }
968 
969 
970 static int
lwp_upimutex_unlock(lwp_mutex_t * lp,uint8_t type)971 lwp_upimutex_unlock(lwp_mutex_t *lp, uint8_t type)
972 {
973 	label_t ljb;
974 	int error = 0;
975 	lwpchan_t lwpchan;
976 	uint16_t flag;
977 	upib_t *upibp;
978 	volatile struct upimutex *upimutex = NULL;
979 	volatile int upilocked = 0;
980 
981 	if (on_fault(&ljb)) {
982 		if (upilocked)
983 			upimutex_unlock((upimutex_t *)upimutex, 0);
984 		error = EFAULT;
985 		goto out;
986 	}
987 	if (!get_lwpchan(curproc->p_as, (caddr_t)lp, type,
988 	    &lwpchan, LWPCHAN_MPPOOL)) {
989 		error = EFAULT;
990 		goto out;
991 	}
992 	upibp = &UPI_CHAIN(lwpchan);
993 	mutex_enter(&upibp->upib_lock);
994 	upimutex = upi_get(upibp, &lwpchan);
995 	/*
996 	 * If the lock is not held, or the owner is not curthread, return
997 	 * error. The user-level wrapper can return this error or stall,
998 	 * depending on whether mutex is of ERRORCHECK type or not.
999 	 */
1000 	if (upimutex == NULL || upimutex->upi_owner != curthread) {
1001 		mutex_exit(&upibp->upib_lock);
1002 		error = EPERM;
1003 		goto out;
1004 	}
1005 	mutex_exit(&upibp->upib_lock); /* release for user memory access */
1006 	upilocked = 1;
1007 	fuword16_noerr(&lp->mutex_flag, &flag);
1008 	if (flag & (LOCK_OWNERDEAD | LOCK_UNMAPPED)) {
1009 		/*
1010 		 * transition mutex to the LOCK_NOTRECOVERABLE state.
1011 		 */
1012 		flag &= ~(LOCK_OWNERDEAD | LOCK_UNMAPPED);
1013 		flag |= LOCK_NOTRECOVERABLE;
1014 		suword16_noerr(&lp->mutex_flag, flag);
1015 	}
1016 	set_owner_pid(lp, 0, 0);
1017 	upimutex_unlock((upimutex_t *)upimutex, flag);
1018 	upilocked = 0;
1019 out:
1020 	no_fault();
1021 	return (error);
1022 }
1023 
1024 /*
1025  * Set the owner and ownerpid fields of a user-level mutex. Note, this function
1026  * uses the suword*_noerr routines which must be called between
1027  * on_fault/no_fault. However, this routine itself does not do the
1028  * on_fault/no_fault and it is assumed all the callers will do so instead!
1029  */
1030 static void
set_owner_pid(lwp_mutex_t * lp,uintptr_t owner,pid_t pid)1031 set_owner_pid(lwp_mutex_t *lp, uintptr_t owner, pid_t pid)
1032 {
1033 	union {
1034 		uint64_t word64;
1035 		uint32_t word32[2];
1036 	} un;
1037 
1038 	un.word64 = (uint64_t)owner;
1039 
1040 	suword32_noerr(&lp->mutex_ownerpid, pid);
1041 #if defined(_LP64)
1042 	if (((uintptr_t)lp & (_LONG_LONG_ALIGNMENT - 1)) == 0) { /* aligned */
1043 		suword64_noerr(&lp->mutex_owner, un.word64);
1044 		return;
1045 	}
1046 #endif
1047 	/* mutex is unaligned or we are running on a 32-bit kernel */
1048 	suword32_noerr((uint32_t *)&lp->mutex_owner, un.word32[0]);
1049 	suword32_noerr((uint32_t *)&lp->mutex_owner + 1, un.word32[1]);
1050 }
1051 
1052 /*
1053  * Clear the contents of a user-level mutex; return the flags.
1054  * Used only by upi_dead() and lwp_mutex_cleanup(), below.
1055  */
1056 static uint16_t
lwp_clear_mutex(lwp_mutex_t * lp,uint16_t lockflg)1057 lwp_clear_mutex(lwp_mutex_t *lp, uint16_t lockflg)
1058 {
1059 	uint16_t flag;
1060 
1061 	fuword16_noerr(&lp->mutex_flag, &flag);
1062 	if ((flag &
1063 	    (LOCK_OWNERDEAD | LOCK_UNMAPPED | LOCK_NOTRECOVERABLE)) == 0) {
1064 		flag |= lockflg;
1065 		suword16_noerr(&lp->mutex_flag, flag);
1066 	}
1067 	set_owner_pid(lp, 0, 0);
1068 	suword8_noerr(&lp->mutex_rcount, 0);
1069 
1070 	return (flag);
1071 }
1072 
1073 /*
1074  * Mark user mutex state, corresponding to kernel upimutex,
1075  * as LOCK_UNMAPPED or LOCK_OWNERDEAD, as appropriate
1076  */
1077 static int
upi_dead(upimutex_t * upip,uint16_t lockflg)1078 upi_dead(upimutex_t *upip, uint16_t lockflg)
1079 {
1080 	label_t ljb;
1081 	int error = 0;
1082 	lwp_mutex_t *lp;
1083 
1084 	if (on_fault(&ljb)) {
1085 		error = EFAULT;
1086 		goto out;
1087 	}
1088 
1089 	lp = upip->upi_vaddr;
1090 	(void) lwp_clear_mutex(lp, lockflg);
1091 	suword8_noerr(&lp->mutex_lockw, 0);
1092 out:
1093 	no_fault();
1094 	return (error);
1095 }
1096 
1097 /*
1098  * Unlock all upimutexes held by curthread, since curthread is dying.
1099  * For each upimutex, attempt to mark its corresponding user mutex object as
1100  * dead.
1101  */
1102 void
upimutex_cleanup()1103 upimutex_cleanup()
1104 {
1105 	kthread_t *t = curthread;
1106 	uint16_t lockflg = (ttoproc(t)->p_proc_flag & P_PR_EXEC)?
1107 	    LOCK_UNMAPPED : LOCK_OWNERDEAD;
1108 	struct upimutex *upip;
1109 
1110 	while ((upip = t->t_upimutex) != NULL) {
1111 		if (upi_dead(upip, lockflg) != 0) {
1112 			/*
1113 			 * If the user object associated with this upimutex is
1114 			 * unmapped, unlock upimutex with the
1115 			 * LOCK_NOTRECOVERABLE flag, so that all waiters are
1116 			 * woken up. Since user object is unmapped, it could
1117 			 * not be marked as dead or notrecoverable.
1118 			 * The waiters will now all wake up and return
1119 			 * ENOTRECOVERABLE, since they would find that the lock
1120 			 * has not been handed-off to them.
1121 			 * See lwp_upimutex_lock().
1122 			 */
1123 			upimutex_unlock(upip, LOCK_NOTRECOVERABLE);
1124 		} else {
1125 			/*
1126 			 * The user object has been updated as dead.
1127 			 * Unlock the upimutex: if no waiters, upip kmem will
1128 			 * be freed. If there is a waiter, the lock will be
1129 			 * handed off. If exit() is in progress, each existing
1130 			 * waiter will successively get the lock, as owners
1131 			 * die, and each new owner will call this routine as
1132 			 * it dies. The last owner will free kmem, since
1133 			 * it will find the upimutex has no waiters. So,
1134 			 * eventually, the kmem is guaranteed to be freed.
1135 			 */
1136 			upimutex_unlock(upip, 0);
1137 		}
1138 		/*
1139 		 * Note that the call to upimutex_unlock() above will delete
1140 		 * upimutex from the t_upimutexes chain. And so the
1141 		 * while loop will eventually terminate.
1142 		 */
1143 	}
1144 }
1145 
1146 int
lwp_mutex_timedlock(lwp_mutex_t * lp,timespec_t * tsp,uintptr_t owner)1147 lwp_mutex_timedlock(lwp_mutex_t *lp, timespec_t *tsp, uintptr_t owner)
1148 {
1149 	kthread_t *t = curthread;
1150 	klwp_t *lwp = ttolwp(t);
1151 	proc_t *p = ttoproc(t);
1152 	lwp_timer_t lwpt;
1153 	caddr_t timedwait;
1154 	int error = 0;
1155 	int time_error;
1156 	clock_t tim = -1;
1157 	uchar_t waiters;
1158 	volatile int locked = 0;
1159 	volatile int watched = 0;
1160 	label_t ljb;
1161 	volatile uint8_t type = 0;
1162 	lwpchan_t lwpchan;
1163 	sleepq_head_t *sqh;
1164 	uint16_t flag;
1165 	int imm_timeout = 0;
1166 
1167 	if ((caddr_t)lp >= p->p_as->a_userlimit)
1168 		return (set_errno(EFAULT));
1169 
1170 	/*
1171 	 * Put the lwp in an orderly state for debugging,
1172 	 * in case we are stopped while sleeping, below.
1173 	 */
1174 	prstop(PR_REQUESTED, 0);
1175 
1176 	timedwait = (caddr_t)tsp;
1177 	if ((time_error = lwp_timer_copyin(&lwpt, tsp)) == 0 &&
1178 	    lwpt.lwpt_imm_timeout) {
1179 		imm_timeout = 1;
1180 		timedwait = NULL;
1181 	}
1182 
1183 	/*
1184 	 * Although LMS_USER_LOCK implies "asleep waiting for user-mode lock",
1185 	 * this micro state is really a run state. If the thread indeed blocks,
1186 	 * this state becomes valid. If not, the state is converted back to
1187 	 * LMS_SYSTEM. So, it is OK to set the mstate here, instead of just
1188 	 * when blocking.
1189 	 */
1190 	(void) new_mstate(t, LMS_USER_LOCK);
1191 	if (on_fault(&ljb)) {
1192 		if (locked)
1193 			lwpchan_unlock(&lwpchan, LWPCHAN_MPPOOL);
1194 		error = EFAULT;
1195 		goto out;
1196 	}
1197 	/*
1198 	 * Force Copy-on-write if necessary and ensure that the
1199 	 * synchronization object resides in read/write memory.
1200 	 * Cause an EFAULT return now if this is not so.
1201 	 */
1202 	fuword8_noerr(&lp->mutex_type, (uint8_t *)&type);
1203 	suword8_noerr(&lp->mutex_type, type);
1204 	if (UPIMUTEX(type)) {
1205 		no_fault();
1206 		error = lwp_upimutex_lock(lp, type, UPIMUTEX_BLOCK, &lwpt);
1207 		if (error == 0 || error == EOWNERDEAD ||
1208 		    error == ELOCKUNMAPPED) {
1209 			volatile int locked = error != 0;
1210 			if (on_fault(&ljb)) {
1211 				if (locked != 0)
1212 					error = lwp_upimutex_unlock(lp, type);
1213 				else
1214 					error = EFAULT;
1215 				goto upierr;
1216 			}
1217 			set_owner_pid(lp, owner,
1218 			    (type & USYNC_PROCESS)? p->p_pid : 0);
1219 			no_fault();
1220 		}
1221 upierr:
1222 		if (tsp && !time_error)	/* copyout the residual time left */
1223 			error = lwp_timer_copyout(&lwpt, error);
1224 		if (error)
1225 			return (set_errno(error));
1226 		return (0);
1227 	}
1228 	if (!get_lwpchan(curproc->p_as, (caddr_t)lp, type,
1229 	    &lwpchan, LWPCHAN_MPPOOL)) {
1230 		error = EFAULT;
1231 		goto out;
1232 	}
1233 	lwpchan_lock(&lwpchan, LWPCHAN_MPPOOL);
1234 	locked = 1;
1235 	if (type & LOCK_ROBUST) {
1236 		fuword16_noerr(&lp->mutex_flag, &flag);
1237 		if (flag & LOCK_NOTRECOVERABLE) {
1238 			lwpchan_unlock(&lwpchan, LWPCHAN_MPPOOL);
1239 			error = ENOTRECOVERABLE;
1240 			goto out;
1241 		}
1242 	}
1243 	fuword8_noerr(&lp->mutex_waiters, &waiters);
1244 	suword8_noerr(&lp->mutex_waiters, 1);
1245 
1246 	/*
1247 	 * If watchpoints are set, they need to be restored, since
1248 	 * atomic accesses of memory such as the call to ulock_try()
1249 	 * below cannot be watched.
1250 	 */
1251 
1252 	watched = watch_disable_addr((caddr_t)lp, sizeof (*lp), S_WRITE);
1253 
1254 	while (!ulock_try(&lp->mutex_lockw)) {
1255 		if (time_error) {
1256 			/*
1257 			 * The SUSV3 Posix spec is very clear that we
1258 			 * should get no error from validating the
1259 			 * timer until we would actually sleep.
1260 			 */
1261 			error = time_error;
1262 			break;
1263 		}
1264 
1265 		if (watched) {
1266 			watch_enable_addr((caddr_t)lp, sizeof (*lp), S_WRITE);
1267 			watched = 0;
1268 		}
1269 
1270 		if (timedwait) {
1271 			/*
1272 			 * If we successfully queue the timeout,
1273 			 * then don't drop t_delay_lock until
1274 			 * we are on the sleep queue (below).
1275 			 */
1276 			mutex_enter(&t->t_delay_lock);
1277 			if (lwp_timer_enqueue(&lwpt) != 0) {
1278 				mutex_exit(&t->t_delay_lock);
1279 				imm_timeout = 1;
1280 				timedwait = NULL;
1281 			}
1282 		}
1283 		lwp_block(&lwpchan);
1284 		/*
1285 		 * Nothing should happen to cause the lwp to go to
1286 		 * sleep again until after it returns from swtch().
1287 		 */
1288 		if (timedwait)
1289 			mutex_exit(&t->t_delay_lock);
1290 		locked = 0;
1291 		lwpchan_unlock(&lwpchan, LWPCHAN_MPPOOL);
1292 		if (ISSIG(t, JUSTLOOKING) || MUSTRETURN(p, t) || imm_timeout)
1293 			setrun(t);
1294 		swtch();
1295 		t->t_flag &= ~T_WAKEABLE;
1296 		if (timedwait)
1297 			tim = lwp_timer_dequeue(&lwpt);
1298 		setallwatch();
1299 		if (ISSIG(t, FORREAL) || lwp->lwp_sysabort || MUSTRETURN(p, t))
1300 			error = EINTR;
1301 		else if (imm_timeout || (timedwait && tim == -1))
1302 			error = ETIME;
1303 		if (error) {
1304 			lwp->lwp_asleep = 0;
1305 			lwp->lwp_sysabort = 0;
1306 			watched = watch_disable_addr((caddr_t)lp, sizeof (*lp),
1307 			    S_WRITE);
1308 
1309 			/*
1310 			 * Need to re-compute waiters bit. The waiters field in
1311 			 * the lock is not reliable. Either of two things could
1312 			 * have occurred: no lwp may have called lwp_release()
1313 			 * for me but I have woken up due to a signal or
1314 			 * timeout.  In this case, the waiter bit is incorrect
1315 			 * since it is still set to 1, set above.
1316 			 * OR an lwp_release() did occur for some other lwp on
1317 			 * the same lwpchan. In this case, the waiter bit is
1318 			 * correct.  But which event occurred, one can't tell.
1319 			 * So, recompute.
1320 			 */
1321 			lwpchan_lock(&lwpchan, LWPCHAN_MPPOOL);
1322 			locked = 1;
1323 			sqh = lwpsqhash(&lwpchan);
1324 			disp_lock_enter(&sqh->sq_lock);
1325 			waiters = iswanted(sqh->sq_queue.sq_first, &lwpchan);
1326 			disp_lock_exit(&sqh->sq_lock);
1327 			break;
1328 		}
1329 		lwp->lwp_asleep = 0;
1330 		watched = watch_disable_addr((caddr_t)lp, sizeof (*lp),
1331 		    S_WRITE);
1332 		lwpchan_lock(&lwpchan, LWPCHAN_MPPOOL);
1333 		locked = 1;
1334 		fuword8_noerr(&lp->mutex_waiters, &waiters);
1335 		suword8_noerr(&lp->mutex_waiters, 1);
1336 		if (type & LOCK_ROBUST) {
1337 			fuword16_noerr(&lp->mutex_flag, &flag);
1338 			if (flag & LOCK_NOTRECOVERABLE) {
1339 				error = ENOTRECOVERABLE;
1340 				break;
1341 			}
1342 		}
1343 	}
1344 
1345 	if (t->t_mstate == LMS_USER_LOCK)
1346 		(void) new_mstate(t, LMS_SYSTEM);
1347 
1348 	if (error == 0) {
1349 		set_owner_pid(lp, owner, (type & USYNC_PROCESS)? p->p_pid : 0);
1350 		if (type & LOCK_ROBUST) {
1351 			fuword16_noerr(&lp->mutex_flag, &flag);
1352 			if (flag & (LOCK_OWNERDEAD | LOCK_UNMAPPED)) {
1353 				if (flag & LOCK_OWNERDEAD)
1354 					error = EOWNERDEAD;
1355 				else if (type & USYNC_PROCESS_ROBUST)
1356 					error = ELOCKUNMAPPED;
1357 				else
1358 					error = EOWNERDEAD;
1359 			}
1360 		}
1361 	}
1362 	suword8_noerr(&lp->mutex_waiters, waiters);
1363 	locked = 0;
1364 	lwpchan_unlock(&lwpchan, LWPCHAN_MPPOOL);
1365 out:
1366 	no_fault();
1367 	if (watched)
1368 		watch_enable_addr((caddr_t)lp, sizeof (*lp), S_WRITE);
1369 	if (tsp && !time_error)		/* copyout the residual time left */
1370 		error = lwp_timer_copyout(&lwpt, error);
1371 	if (error)
1372 		return (set_errno(error));
1373 	return (0);
1374 }
1375 
1376 static int
iswanted(kthread_t * t,lwpchan_t * lwpchan)1377 iswanted(kthread_t *t, lwpchan_t *lwpchan)
1378 {
1379 	/*
1380 	 * The caller holds the dispatcher lock on the sleep queue.
1381 	 */
1382 	while (t != NULL) {
1383 		if (t->t_lwpchan.lc_wchan0 == lwpchan->lc_wchan0 &&
1384 		    t->t_lwpchan.lc_wchan == lwpchan->lc_wchan)
1385 			return (1);
1386 		t = t->t_link;
1387 	}
1388 	return (0);
1389 }
1390 
1391 /*
1392  * Return the highest priority thread sleeping on this lwpchan.
1393  */
1394 static kthread_t *
lwp_queue_waiter(lwpchan_t * lwpchan)1395 lwp_queue_waiter(lwpchan_t *lwpchan)
1396 {
1397 	sleepq_head_t *sqh;
1398 	kthread_t *tp;
1399 
1400 	sqh = lwpsqhash(lwpchan);
1401 	disp_lock_enter(&sqh->sq_lock);		/* lock the sleep queue */
1402 	for (tp = sqh->sq_queue.sq_first; tp != NULL; tp = tp->t_link) {
1403 		if (tp->t_lwpchan.lc_wchan0 == lwpchan->lc_wchan0 &&
1404 		    tp->t_lwpchan.lc_wchan == lwpchan->lc_wchan)
1405 			break;
1406 	}
1407 	disp_lock_exit(&sqh->sq_lock);
1408 	return (tp);
1409 }
1410 
1411 static int
lwp_release(lwpchan_t * lwpchan,uchar_t * waiters,int sync_type)1412 lwp_release(lwpchan_t *lwpchan, uchar_t *waiters, int sync_type)
1413 {
1414 	sleepq_head_t *sqh;
1415 	kthread_t *tp;
1416 	kthread_t **tpp;
1417 
1418 	sqh = lwpsqhash(lwpchan);
1419 	disp_lock_enter(&sqh->sq_lock);		/* lock the sleep queue */
1420 	tpp = &sqh->sq_queue.sq_first;
1421 	while ((tp = *tpp) != NULL) {
1422 		if (tp->t_lwpchan.lc_wchan0 == lwpchan->lc_wchan0 &&
1423 		    tp->t_lwpchan.lc_wchan == lwpchan->lc_wchan) {
1424 			/*
1425 			 * The following is typically false. It could be true
1426 			 * only if lwp_release() is called from
1427 			 * lwp_mutex_wakeup() after reading the waiters field
1428 			 * from memory in which the lwp lock used to be, but has
1429 			 * since been re-used to hold a lwp cv or lwp semaphore.
1430 			 * The thread "tp" found to match the lwp lock's wchan
1431 			 * is actually sleeping for the cv or semaphore which
1432 			 * now has the same wchan. In this case, lwp_release()
1433 			 * should return failure.
1434 			 */
1435 			if (sync_type != (tp->t_flag & T_WAITCVSEM)) {
1436 				ASSERT(sync_type == 0);
1437 				/*
1438 				 * assert that this can happen only for mutexes
1439 				 * i.e. sync_type == 0, for correctly written
1440 				 * user programs.
1441 				 */
1442 				disp_lock_exit(&sqh->sq_lock);
1443 				return (0);
1444 			}
1445 			*waiters = iswanted(tp->t_link, lwpchan);
1446 			sleepq_unlink(tpp, tp);
1447 			DTRACE_SCHED1(wakeup, kthread_t *, tp);
1448 			tp->t_wchan0 = NULL;
1449 			tp->t_wchan = NULL;
1450 			tp->t_sobj_ops = NULL;
1451 			tp->t_release = 1;
1452 			THREAD_TRANSITION(tp);	/* drops sleepq lock */
1453 			CL_WAKEUP(tp);
1454 			thread_unlock(tp);	/* drop run queue lock */
1455 			return (1);
1456 		}
1457 		tpp = &tp->t_link;
1458 	}
1459 	*waiters = 0;
1460 	disp_lock_exit(&sqh->sq_lock);
1461 	return (0);
1462 }
1463 
1464 static void
lwp_release_all(lwpchan_t * lwpchan)1465 lwp_release_all(lwpchan_t *lwpchan)
1466 {
1467 	sleepq_head_t	*sqh;
1468 	kthread_t *tp;
1469 	kthread_t **tpp;
1470 
1471 	sqh = lwpsqhash(lwpchan);
1472 	disp_lock_enter(&sqh->sq_lock);		/* lock sleep q queue */
1473 	tpp = &sqh->sq_queue.sq_first;
1474 	while ((tp = *tpp) != NULL) {
1475 		if (tp->t_lwpchan.lc_wchan0 == lwpchan->lc_wchan0 &&
1476 		    tp->t_lwpchan.lc_wchan == lwpchan->lc_wchan) {
1477 			sleepq_unlink(tpp, tp);
1478 			DTRACE_SCHED1(wakeup, kthread_t *, tp);
1479 			tp->t_wchan0 = NULL;
1480 			tp->t_wchan = NULL;
1481 			tp->t_sobj_ops = NULL;
1482 			CL_WAKEUP(tp);
1483 			thread_unlock_high(tp);	/* release run queue lock */
1484 		} else {
1485 			tpp = &tp->t_link;
1486 		}
1487 	}
1488 	disp_lock_exit(&sqh->sq_lock);		/* drop sleep q lock */
1489 }
1490 
1491 /*
1492  * unblock a lwp that is trying to acquire this mutex. the blocked
1493  * lwp resumes and retries to acquire the lock.
1494  */
1495 int
lwp_mutex_wakeup(lwp_mutex_t * lp,int release_all)1496 lwp_mutex_wakeup(lwp_mutex_t *lp, int release_all)
1497 {
1498 	proc_t *p = ttoproc(curthread);
1499 	lwpchan_t lwpchan;
1500 	uchar_t waiters;
1501 	volatile int locked = 0;
1502 	volatile int watched = 0;
1503 	volatile uint8_t type = 0;
1504 	label_t ljb;
1505 	int error = 0;
1506 
1507 	if ((caddr_t)lp >= p->p_as->a_userlimit)
1508 		return (set_errno(EFAULT));
1509 
1510 	watched = watch_disable_addr((caddr_t)lp, sizeof (*lp), S_WRITE);
1511 
1512 	if (on_fault(&ljb)) {
1513 		if (locked)
1514 			lwpchan_unlock(&lwpchan, LWPCHAN_MPPOOL);
1515 		error = EFAULT;
1516 		goto out;
1517 	}
1518 	/*
1519 	 * Force Copy-on-write if necessary and ensure that the
1520 	 * synchronization object resides in read/write memory.
1521 	 * Cause an EFAULT return now if this is not so.
1522 	 */
1523 	fuword8_noerr(&lp->mutex_type, (uint8_t *)&type);
1524 	suword8_noerr(&lp->mutex_type, type);
1525 	if (!get_lwpchan(curproc->p_as, (caddr_t)lp, type,
1526 	    &lwpchan, LWPCHAN_MPPOOL)) {
1527 		error = EFAULT;
1528 		goto out;
1529 	}
1530 	lwpchan_lock(&lwpchan, LWPCHAN_MPPOOL);
1531 	locked = 1;
1532 	/*
1533 	 * Always wake up an lwp (if any) waiting on lwpchan. The woken lwp will
1534 	 * re-try the lock in lwp_mutex_timedlock(). The call to lwp_release()
1535 	 * may fail.  If it fails, do not write into the waiter bit.
1536 	 * The call to lwp_release() might fail due to one of three reasons:
1537 	 *
1538 	 * 	1. due to the thread which set the waiter bit not actually
1539 	 *	   sleeping since it got the lock on the re-try. The waiter
1540 	 *	   bit will then be correctly updated by that thread. This
1541 	 *	   window may be closed by reading the wait bit again here
1542 	 *	   and not calling lwp_release() at all if it is zero.
1543 	 *	2. the thread which set the waiter bit and went to sleep
1544 	 *	   was woken up by a signal. This time, the waiter recomputes
1545 	 *	   the wait bit in the return with EINTR code.
1546 	 *	3. the waiter bit read by lwp_mutex_wakeup() was in
1547 	 *	   memory that has been re-used after the lock was dropped.
1548 	 *	   In this case, writing into the waiter bit would cause data
1549 	 *	   corruption.
1550 	 */
1551 	if (release_all)
1552 		lwp_release_all(&lwpchan);
1553 	else if (lwp_release(&lwpchan, &waiters, 0))
1554 		suword8_noerr(&lp->mutex_waiters, waiters);
1555 	lwpchan_unlock(&lwpchan, LWPCHAN_MPPOOL);
1556 out:
1557 	no_fault();
1558 	if (watched)
1559 		watch_enable_addr((caddr_t)lp, sizeof (*lp), S_WRITE);
1560 	if (error)
1561 		return (set_errno(error));
1562 	return (0);
1563 }
1564 
1565 /*
1566  * lwp_cond_wait() has four arguments, a pointer to a condition variable,
1567  * a pointer to a mutex, a pointer to a timespec for a timed wait and
1568  * a flag telling the kernel whether or not to honor the kernel/user
1569  * schedctl parking protocol (see schedctl_is_park() in schedctl.c).
1570  * The kernel puts the lwp to sleep on a unique pair of caddr_t's called an
1571  * lwpchan, returned by get_lwpchan().  If the timespec pointer is non-NULL,
1572  * it is used an an in/out parameter.  On entry, it contains the relative
1573  * time until timeout.  On exit, we copyout the residual time left to it.
1574  */
1575 int
lwp_cond_wait(lwp_cond_t * cv,lwp_mutex_t * mp,timespec_t * tsp,int check_park)1576 lwp_cond_wait(lwp_cond_t *cv, lwp_mutex_t *mp, timespec_t *tsp, int check_park)
1577 {
1578 	kthread_t *t = curthread;
1579 	klwp_t *lwp = ttolwp(t);
1580 	proc_t *p = ttoproc(t);
1581 	lwp_timer_t lwpt;
1582 	lwpchan_t cv_lwpchan;
1583 	lwpchan_t m_lwpchan;
1584 	caddr_t timedwait;
1585 	volatile uint16_t type = 0;
1586 	volatile uint8_t mtype = 0;
1587 	uchar_t waiters;
1588 	volatile int error;
1589 	clock_t tim = -1;
1590 	volatile int locked = 0;
1591 	volatile int m_locked = 0;
1592 	volatile int cvwatched = 0;
1593 	volatile int mpwatched = 0;
1594 	label_t ljb;
1595 	volatile int no_lwpchan = 1;
1596 	int imm_timeout = 0;
1597 	int imm_unpark = 0;
1598 
1599 	if ((caddr_t)cv >= p->p_as->a_userlimit ||
1600 	    (caddr_t)mp >= p->p_as->a_userlimit)
1601 		return (set_errno(EFAULT));
1602 
1603 	/*
1604 	 * Put the lwp in an orderly state for debugging,
1605 	 * in case we are stopped while sleeping, below.
1606 	 */
1607 	prstop(PR_REQUESTED, 0);
1608 
1609 	timedwait = (caddr_t)tsp;
1610 	if ((error = lwp_timer_copyin(&lwpt, tsp)) != 0)
1611 		return (set_errno(error));
1612 	if (lwpt.lwpt_imm_timeout) {
1613 		imm_timeout = 1;
1614 		timedwait = NULL;
1615 	}
1616 
1617 	(void) new_mstate(t, LMS_USER_LOCK);
1618 
1619 	if (on_fault(&ljb)) {
1620 		if (no_lwpchan) {
1621 			error = EFAULT;
1622 			goto out;
1623 		}
1624 		if (m_locked) {
1625 			m_locked = 0;
1626 			lwpchan_unlock(&m_lwpchan, LWPCHAN_MPPOOL);
1627 		}
1628 		if (locked) {
1629 			locked = 0;
1630 			lwpchan_unlock(&cv_lwpchan, LWPCHAN_CVPOOL);
1631 		}
1632 		/*
1633 		 * set up another on_fault() for a possible fault
1634 		 * on the user lock accessed at "efault"
1635 		 */
1636 		if (on_fault(&ljb)) {
1637 			if (m_locked) {
1638 				m_locked = 0;
1639 				lwpchan_unlock(&m_lwpchan, LWPCHAN_MPPOOL);
1640 			}
1641 			goto out;
1642 		}
1643 		error = EFAULT;
1644 		goto efault;
1645 	}
1646 
1647 	/*
1648 	 * Force Copy-on-write if necessary and ensure that the
1649 	 * synchronization object resides in read/write memory.
1650 	 * Cause an EFAULT return now if this is not so.
1651 	 */
1652 	fuword8_noerr(&mp->mutex_type, (uint8_t *)&mtype);
1653 	suword8_noerr(&mp->mutex_type, mtype);
1654 	if (UPIMUTEX(mtype) == 0) {
1655 		/* convert user level mutex, "mp", to a unique lwpchan */
1656 		/* check if mtype is ok to use below, instead of type from cv */
1657 		if (!get_lwpchan(p->p_as, (caddr_t)mp, mtype,
1658 		    &m_lwpchan, LWPCHAN_MPPOOL)) {
1659 			error = EFAULT;
1660 			goto out;
1661 		}
1662 	}
1663 	fuword16_noerr(&cv->cond_type, (uint16_t *)&type);
1664 	suword16_noerr(&cv->cond_type, type);
1665 	/* convert user level condition variable, "cv", to a unique lwpchan */
1666 	if (!get_lwpchan(p->p_as, (caddr_t)cv, type,
1667 	    &cv_lwpchan, LWPCHAN_CVPOOL)) {
1668 		error = EFAULT;
1669 		goto out;
1670 	}
1671 	no_lwpchan = 0;
1672 	cvwatched = watch_disable_addr((caddr_t)cv, sizeof (*cv), S_WRITE);
1673 	if (UPIMUTEX(mtype) == 0)
1674 		mpwatched = watch_disable_addr((caddr_t)mp, sizeof (*mp),
1675 		    S_WRITE);
1676 
1677 	/*
1678 	 * lwpchan_lock ensures that the calling lwp is put to sleep atomically
1679 	 * with respect to a possible wakeup which is a result of either
1680 	 * an lwp_cond_signal() or an lwp_cond_broadcast().
1681 	 *
1682 	 * What's misleading, is that the lwp is put to sleep after the
1683 	 * condition variable's mutex is released.  This is OK as long as
1684 	 * the release operation is also done while holding lwpchan_lock.
1685 	 * The lwp is then put to sleep when the possibility of pagefaulting
1686 	 * or sleeping is completely eliminated.
1687 	 */
1688 	lwpchan_lock(&cv_lwpchan, LWPCHAN_CVPOOL);
1689 	locked = 1;
1690 	if (UPIMUTEX(mtype) == 0) {
1691 		lwpchan_lock(&m_lwpchan, LWPCHAN_MPPOOL);
1692 		m_locked = 1;
1693 		suword8_noerr(&cv->cond_waiters_kernel, 1);
1694 		/*
1695 		 * unlock the condition variable's mutex. (pagefaults are
1696 		 * possible here.)
1697 		 */
1698 		set_owner_pid(mp, 0, 0);
1699 		ulock_clear(&mp->mutex_lockw);
1700 		fuword8_noerr(&mp->mutex_waiters, &waiters);
1701 		if (waiters != 0) {
1702 			/*
1703 			 * Given the locking of lwpchan_lock around the release
1704 			 * of the mutex and checking for waiters, the following
1705 			 * call to lwp_release() can fail ONLY if the lock
1706 			 * acquirer is interrupted after setting the waiter bit,
1707 			 * calling lwp_block() and releasing lwpchan_lock.
1708 			 * In this case, it could get pulled off the lwp sleep
1709 			 * q (via setrun()) before the following call to
1710 			 * lwp_release() occurs. In this case, the lock
1711 			 * requestor will update the waiter bit correctly by
1712 			 * re-evaluating it.
1713 			 */
1714 			if (lwp_release(&m_lwpchan, &waiters, 0))
1715 				suword8_noerr(&mp->mutex_waiters, waiters);
1716 		}
1717 		m_locked = 0;
1718 		lwpchan_unlock(&m_lwpchan, LWPCHAN_MPPOOL);
1719 	} else {
1720 		suword8_noerr(&cv->cond_waiters_kernel, 1);
1721 		error = lwp_upimutex_unlock(mp, mtype);
1722 		if (error) {	/* if the upimutex unlock failed */
1723 			locked = 0;
1724 			lwpchan_unlock(&cv_lwpchan, LWPCHAN_CVPOOL);
1725 			goto out;
1726 		}
1727 	}
1728 	no_fault();
1729 
1730 	if (mpwatched) {
1731 		watch_enable_addr((caddr_t)mp, sizeof (*mp), S_WRITE);
1732 		mpwatched = 0;
1733 	}
1734 	if (cvwatched) {
1735 		watch_enable_addr((caddr_t)cv, sizeof (*cv), S_WRITE);
1736 		cvwatched = 0;
1737 	}
1738 
1739 	if (check_park && (!schedctl_is_park() || t->t_unpark)) {
1740 		/*
1741 		 * We received a signal at user-level before calling here
1742 		 * or another thread wants us to return immediately
1743 		 * with EINTR.  See lwp_unpark().
1744 		 */
1745 		imm_unpark = 1;
1746 		t->t_unpark = 0;
1747 		timedwait = NULL;
1748 	} else if (timedwait) {
1749 		/*
1750 		 * If we successfully queue the timeout,
1751 		 * then don't drop t_delay_lock until
1752 		 * we are on the sleep queue (below).
1753 		 */
1754 		mutex_enter(&t->t_delay_lock);
1755 		if (lwp_timer_enqueue(&lwpt) != 0) {
1756 			mutex_exit(&t->t_delay_lock);
1757 			imm_timeout = 1;
1758 			timedwait = NULL;
1759 		}
1760 	}
1761 	t->t_flag |= T_WAITCVSEM;
1762 	lwp_block(&cv_lwpchan);
1763 	/*
1764 	 * Nothing should happen to cause the lwp to go to sleep
1765 	 * until after it returns from swtch().
1766 	 */
1767 	if (timedwait)
1768 		mutex_exit(&t->t_delay_lock);
1769 	locked = 0;
1770 	lwpchan_unlock(&cv_lwpchan, LWPCHAN_CVPOOL);
1771 	if (ISSIG(t, JUSTLOOKING) || MUSTRETURN(p, t) ||
1772 	    (imm_timeout | imm_unpark))
1773 		setrun(t);
1774 	swtch();
1775 	t->t_flag &= ~(T_WAITCVSEM | T_WAKEABLE);
1776 	if (timedwait)
1777 		tim = lwp_timer_dequeue(&lwpt);
1778 	if (ISSIG(t, FORREAL) || lwp->lwp_sysabort ||
1779 	    MUSTRETURN(p, t) || imm_unpark)
1780 		error = EINTR;
1781 	else if (imm_timeout || (timedwait && tim == -1))
1782 		error = ETIME;
1783 	lwp->lwp_asleep = 0;
1784 	lwp->lwp_sysabort = 0;
1785 	setallwatch();
1786 
1787 	if (t->t_mstate == LMS_USER_LOCK)
1788 		(void) new_mstate(t, LMS_SYSTEM);
1789 
1790 	if (tsp && check_park)		/* copyout the residual time left */
1791 		error = lwp_timer_copyout(&lwpt, error);
1792 
1793 	/* the mutex is reacquired by the caller on return to user level */
1794 	if (error) {
1795 		/*
1796 		 * If we were concurrently lwp_cond_signal()d and we
1797 		 * received a UNIX signal or got a timeout, then perform
1798 		 * another lwp_cond_signal() to avoid consuming the wakeup.
1799 		 */
1800 		if (t->t_release)
1801 			(void) lwp_cond_signal(cv);
1802 		return (set_errno(error));
1803 	}
1804 	return (0);
1805 
1806 efault:
1807 	/*
1808 	 * make sure that the user level lock is dropped before
1809 	 * returning to caller, since the caller always re-acquires it.
1810 	 */
1811 	if (UPIMUTEX(mtype) == 0) {
1812 		lwpchan_lock(&m_lwpchan, LWPCHAN_MPPOOL);
1813 		m_locked = 1;
1814 		set_owner_pid(mp, 0, 0);
1815 		ulock_clear(&mp->mutex_lockw);
1816 		fuword8_noerr(&mp->mutex_waiters, &waiters);
1817 		if (waiters != 0) {
1818 			/*
1819 			 * See comment above on lock clearing and lwp_release()
1820 			 * success/failure.
1821 			 */
1822 			if (lwp_release(&m_lwpchan, &waiters, 0))
1823 				suword8_noerr(&mp->mutex_waiters, waiters);
1824 		}
1825 		m_locked = 0;
1826 		lwpchan_unlock(&m_lwpchan, LWPCHAN_MPPOOL);
1827 	} else {
1828 		(void) lwp_upimutex_unlock(mp, mtype);
1829 	}
1830 out:
1831 	no_fault();
1832 	if (mpwatched)
1833 		watch_enable_addr((caddr_t)mp, sizeof (*mp), S_WRITE);
1834 	if (cvwatched)
1835 		watch_enable_addr((caddr_t)cv, sizeof (*cv), S_WRITE);
1836 	if (t->t_mstate == LMS_USER_LOCK)
1837 		(void) new_mstate(t, LMS_SYSTEM);
1838 	return (set_errno(error));
1839 }
1840 
1841 /*
1842  * wakeup one lwp that's blocked on this condition variable.
1843  */
1844 int
lwp_cond_signal(lwp_cond_t * cv)1845 lwp_cond_signal(lwp_cond_t *cv)
1846 {
1847 	proc_t *p = ttoproc(curthread);
1848 	lwpchan_t lwpchan;
1849 	uchar_t waiters;
1850 	volatile uint16_t type = 0;
1851 	volatile int locked = 0;
1852 	volatile int watched = 0;
1853 	label_t ljb;
1854 	int error = 0;
1855 
1856 	if ((caddr_t)cv >= p->p_as->a_userlimit)
1857 		return (set_errno(EFAULT));
1858 
1859 	watched = watch_disable_addr((caddr_t)cv, sizeof (*cv), S_WRITE);
1860 
1861 	if (on_fault(&ljb)) {
1862 		if (locked)
1863 			lwpchan_unlock(&lwpchan, LWPCHAN_CVPOOL);
1864 		error = EFAULT;
1865 		goto out;
1866 	}
1867 	/*
1868 	 * Force Copy-on-write if necessary and ensure that the
1869 	 * synchronization object resides in read/write memory.
1870 	 * Cause an EFAULT return now if this is not so.
1871 	 */
1872 	fuword16_noerr(&cv->cond_type, (uint16_t *)&type);
1873 	suword16_noerr(&cv->cond_type, type);
1874 	if (!get_lwpchan(curproc->p_as, (caddr_t)cv, type,
1875 	    &lwpchan, LWPCHAN_CVPOOL)) {
1876 		error = EFAULT;
1877 		goto out;
1878 	}
1879 	lwpchan_lock(&lwpchan, LWPCHAN_CVPOOL);
1880 	locked = 1;
1881 	fuword8_noerr(&cv->cond_waiters_kernel, &waiters);
1882 	if (waiters != 0) {
1883 		/*
1884 		 * The following call to lwp_release() might fail but it is
1885 		 * OK to write into the waiters bit below, since the memory
1886 		 * could not have been re-used or unmapped (for correctly
1887 		 * written user programs) as in the case of lwp_mutex_wakeup().
1888 		 * For an incorrect program, we should not care about data
1889 		 * corruption since this is just one instance of other places
1890 		 * where corruption can occur for such a program. Of course
1891 		 * if the memory is unmapped, normal fault recovery occurs.
1892 		 */
1893 		(void) lwp_release(&lwpchan, &waiters, T_WAITCVSEM);
1894 		suword8_noerr(&cv->cond_waiters_kernel, waiters);
1895 	}
1896 	lwpchan_unlock(&lwpchan, LWPCHAN_CVPOOL);
1897 out:
1898 	no_fault();
1899 	if (watched)
1900 		watch_enable_addr((caddr_t)cv, sizeof (*cv), S_WRITE);
1901 	if (error)
1902 		return (set_errno(error));
1903 	return (0);
1904 }
1905 
1906 /*
1907  * wakeup every lwp that's blocked on this condition variable.
1908  */
1909 int
lwp_cond_broadcast(lwp_cond_t * cv)1910 lwp_cond_broadcast(lwp_cond_t *cv)
1911 {
1912 	proc_t *p = ttoproc(curthread);
1913 	lwpchan_t lwpchan;
1914 	volatile uint16_t type = 0;
1915 	volatile int locked = 0;
1916 	volatile int watched = 0;
1917 	label_t ljb;
1918 	uchar_t waiters;
1919 	int error = 0;
1920 
1921 	if ((caddr_t)cv >= p->p_as->a_userlimit)
1922 		return (set_errno(EFAULT));
1923 
1924 	watched = watch_disable_addr((caddr_t)cv, sizeof (*cv), S_WRITE);
1925 
1926 	if (on_fault(&ljb)) {
1927 		if (locked)
1928 			lwpchan_unlock(&lwpchan, LWPCHAN_CVPOOL);
1929 		error = EFAULT;
1930 		goto out;
1931 	}
1932 	/*
1933 	 * Force Copy-on-write if necessary and ensure that the
1934 	 * synchronization object resides in read/write memory.
1935 	 * Cause an EFAULT return now if this is not so.
1936 	 */
1937 	fuword16_noerr(&cv->cond_type, (uint16_t *)&type);
1938 	suword16_noerr(&cv->cond_type, type);
1939 	if (!get_lwpchan(curproc->p_as, (caddr_t)cv, type,
1940 	    &lwpchan, LWPCHAN_CVPOOL)) {
1941 		error = EFAULT;
1942 		goto out;
1943 	}
1944 	lwpchan_lock(&lwpchan, LWPCHAN_CVPOOL);
1945 	locked = 1;
1946 	fuword8_noerr(&cv->cond_waiters_kernel, &waiters);
1947 	if (waiters != 0) {
1948 		lwp_release_all(&lwpchan);
1949 		suword8_noerr(&cv->cond_waiters_kernel, 0);
1950 	}
1951 	lwpchan_unlock(&lwpchan, LWPCHAN_CVPOOL);
1952 out:
1953 	no_fault();
1954 	if (watched)
1955 		watch_enable_addr((caddr_t)cv, sizeof (*cv), S_WRITE);
1956 	if (error)
1957 		return (set_errno(error));
1958 	return (0);
1959 }
1960 
1961 int
lwp_sema_trywait(lwp_sema_t * sp)1962 lwp_sema_trywait(lwp_sema_t *sp)
1963 {
1964 	kthread_t *t = curthread;
1965 	proc_t *p = ttoproc(t);
1966 	label_t ljb;
1967 	volatile int locked = 0;
1968 	volatile int watched = 0;
1969 	volatile uint16_t type = 0;
1970 	int count;
1971 	lwpchan_t lwpchan;
1972 	uchar_t waiters;
1973 	int error = 0;
1974 
1975 	if ((caddr_t)sp >= p->p_as->a_userlimit)
1976 		return (set_errno(EFAULT));
1977 
1978 	watched = watch_disable_addr((caddr_t)sp, sizeof (*sp), S_WRITE);
1979 
1980 	if (on_fault(&ljb)) {
1981 		if (locked)
1982 			lwpchan_unlock(&lwpchan, LWPCHAN_CVPOOL);
1983 		error = EFAULT;
1984 		goto out;
1985 	}
1986 	/*
1987 	 * Force Copy-on-write if necessary and ensure that the
1988 	 * synchronization object resides in read/write memory.
1989 	 * Cause an EFAULT return now if this is not so.
1990 	 */
1991 	fuword16_noerr((void *)&sp->sema_type, (uint16_t *)&type);
1992 	suword16_noerr((void *)&sp->sema_type, type);
1993 	if (!get_lwpchan(p->p_as, (caddr_t)sp, type,
1994 	    &lwpchan, LWPCHAN_CVPOOL)) {
1995 		error = EFAULT;
1996 		goto out;
1997 	}
1998 	lwpchan_lock(&lwpchan, LWPCHAN_CVPOOL);
1999 	locked = 1;
2000 	fuword32_noerr((void *)&sp->sema_count, (uint32_t *)&count);
2001 	if (count == 0)
2002 		error = EBUSY;
2003 	else
2004 		suword32_noerr((void *)&sp->sema_count, --count);
2005 	if (count != 0) {
2006 		fuword8_noerr(&sp->sema_waiters, &waiters);
2007 		if (waiters != 0) {
2008 			(void) lwp_release(&lwpchan, &waiters, T_WAITCVSEM);
2009 			suword8_noerr(&sp->sema_waiters, waiters);
2010 		}
2011 	}
2012 	lwpchan_unlock(&lwpchan, LWPCHAN_CVPOOL);
2013 out:
2014 	no_fault();
2015 	if (watched)
2016 		watch_enable_addr((caddr_t)sp, sizeof (*sp), S_WRITE);
2017 	if (error)
2018 		return (set_errno(error));
2019 	return (0);
2020 }
2021 
2022 /*
2023  * See lwp_cond_wait(), above, for an explanation of the 'check_park' argument.
2024  */
2025 int
lwp_sema_timedwait(lwp_sema_t * sp,timespec_t * tsp,int check_park)2026 lwp_sema_timedwait(lwp_sema_t *sp, timespec_t *tsp, int check_park)
2027 {
2028 	kthread_t *t = curthread;
2029 	klwp_t *lwp = ttolwp(t);
2030 	proc_t *p = ttoproc(t);
2031 	lwp_timer_t lwpt;
2032 	caddr_t timedwait;
2033 	clock_t tim = -1;
2034 	label_t ljb;
2035 	volatile int locked = 0;
2036 	volatile int watched = 0;
2037 	volatile uint16_t type = 0;
2038 	int count;
2039 	lwpchan_t lwpchan;
2040 	uchar_t waiters;
2041 	int error = 0;
2042 	int time_error;
2043 	int imm_timeout = 0;
2044 	int imm_unpark = 0;
2045 
2046 	if ((caddr_t)sp >= p->p_as->a_userlimit)
2047 		return (set_errno(EFAULT));
2048 
2049 	/*
2050 	 * Put the lwp in an orderly state for debugging,
2051 	 * in case we are stopped while sleeping, below.
2052 	 */
2053 	prstop(PR_REQUESTED, 0);
2054 
2055 	timedwait = (caddr_t)tsp;
2056 	if ((time_error = lwp_timer_copyin(&lwpt, tsp)) == 0 &&
2057 	    lwpt.lwpt_imm_timeout) {
2058 		imm_timeout = 1;
2059 		timedwait = NULL;
2060 	}
2061 
2062 	watched = watch_disable_addr((caddr_t)sp, sizeof (*sp), S_WRITE);
2063 
2064 	if (on_fault(&ljb)) {
2065 		if (locked)
2066 			lwpchan_unlock(&lwpchan, LWPCHAN_CVPOOL);
2067 		error = EFAULT;
2068 		goto out;
2069 	}
2070 	/*
2071 	 * Force Copy-on-write if necessary and ensure that the
2072 	 * synchronization object resides in read/write memory.
2073 	 * Cause an EFAULT return now if this is not so.
2074 	 */
2075 	fuword16_noerr((void *)&sp->sema_type, (uint16_t *)&type);
2076 	suword16_noerr((void *)&sp->sema_type, type);
2077 	if (!get_lwpchan(p->p_as, (caddr_t)sp, type,
2078 	    &lwpchan, LWPCHAN_CVPOOL)) {
2079 		error = EFAULT;
2080 		goto out;
2081 	}
2082 	lwpchan_lock(&lwpchan, LWPCHAN_CVPOOL);
2083 	locked = 1;
2084 	fuword32_noerr((void *)&sp->sema_count, (uint32_t *)&count);
2085 	while (error == 0 && count == 0) {
2086 		if (time_error) {
2087 			/*
2088 			 * The SUSV3 Posix spec is very clear that we
2089 			 * should get no error from validating the
2090 			 * timer until we would actually sleep.
2091 			 */
2092 			error = time_error;
2093 			break;
2094 		}
2095 		suword8_noerr(&sp->sema_waiters, 1);
2096 		if (watched)
2097 			watch_enable_addr((caddr_t)sp, sizeof (*sp), S_WRITE);
2098 		if (check_park && (!schedctl_is_park() || t->t_unpark)) {
2099 			/*
2100 			 * We received a signal at user-level before calling
2101 			 * here or another thread wants us to return
2102 			 * immediately with EINTR.  See lwp_unpark().
2103 			 */
2104 			imm_unpark = 1;
2105 			t->t_unpark = 0;
2106 			timedwait = NULL;
2107 		} else if (timedwait) {
2108 			/*
2109 			 * If we successfully queue the timeout,
2110 			 * then don't drop t_delay_lock until
2111 			 * we are on the sleep queue (below).
2112 			 */
2113 			mutex_enter(&t->t_delay_lock);
2114 			if (lwp_timer_enqueue(&lwpt) != 0) {
2115 				mutex_exit(&t->t_delay_lock);
2116 				imm_timeout = 1;
2117 				timedwait = NULL;
2118 			}
2119 		}
2120 		t->t_flag |= T_WAITCVSEM;
2121 		lwp_block(&lwpchan);
2122 		/*
2123 		 * Nothing should happen to cause the lwp to sleep
2124 		 * again until after it returns from swtch().
2125 		 */
2126 		if (timedwait)
2127 			mutex_exit(&t->t_delay_lock);
2128 		locked = 0;
2129 		lwpchan_unlock(&lwpchan, LWPCHAN_CVPOOL);
2130 		if (ISSIG(t, JUSTLOOKING) || MUSTRETURN(p, t) ||
2131 		    (imm_timeout | imm_unpark))
2132 			setrun(t);
2133 		swtch();
2134 		t->t_flag &= ~(T_WAITCVSEM | T_WAKEABLE);
2135 		if (timedwait)
2136 			tim = lwp_timer_dequeue(&lwpt);
2137 		setallwatch();
2138 		if (ISSIG(t, FORREAL) || lwp->lwp_sysabort ||
2139 		    MUSTRETURN(p, t) || imm_unpark)
2140 			error = EINTR;
2141 		else if (imm_timeout || (timedwait && tim == -1))
2142 			error = ETIME;
2143 		lwp->lwp_asleep = 0;
2144 		lwp->lwp_sysabort = 0;
2145 		watched = watch_disable_addr((caddr_t)sp,
2146 		    sizeof (*sp), S_WRITE);
2147 		lwpchan_lock(&lwpchan, LWPCHAN_CVPOOL);
2148 		locked = 1;
2149 		fuword32_noerr((void *)&sp->sema_count, (uint32_t *)&count);
2150 	}
2151 	if (error == 0)
2152 		suword32_noerr((void *)&sp->sema_count, --count);
2153 	if (count != 0) {
2154 		(void) lwp_release(&lwpchan, &waiters, T_WAITCVSEM);
2155 		suword8_noerr(&sp->sema_waiters, waiters);
2156 	}
2157 	lwpchan_unlock(&lwpchan, LWPCHAN_CVPOOL);
2158 out:
2159 	no_fault();
2160 	if (watched)
2161 		watch_enable_addr((caddr_t)sp, sizeof (*sp), S_WRITE);
2162 	if (tsp && check_park && !time_error)
2163 		error = lwp_timer_copyout(&lwpt, error);
2164 	if (error)
2165 		return (set_errno(error));
2166 	return (0);
2167 }
2168 
2169 int
lwp_sema_post(lwp_sema_t * sp)2170 lwp_sema_post(lwp_sema_t *sp)
2171 {
2172 	proc_t *p = ttoproc(curthread);
2173 	label_t ljb;
2174 	volatile int locked = 0;
2175 	volatile int watched = 0;
2176 	volatile uint16_t type = 0;
2177 	int count;
2178 	lwpchan_t lwpchan;
2179 	uchar_t waiters;
2180 	int error = 0;
2181 
2182 	if ((caddr_t)sp >= p->p_as->a_userlimit)
2183 		return (set_errno(EFAULT));
2184 
2185 	watched = watch_disable_addr((caddr_t)sp, sizeof (*sp), S_WRITE);
2186 
2187 	if (on_fault(&ljb)) {
2188 		if (locked)
2189 			lwpchan_unlock(&lwpchan, LWPCHAN_CVPOOL);
2190 		error = EFAULT;
2191 		goto out;
2192 	}
2193 	/*
2194 	 * Force Copy-on-write if necessary and ensure that the
2195 	 * synchronization object resides in read/write memory.
2196 	 * Cause an EFAULT return now if this is not so.
2197 	 */
2198 	fuword16_noerr(&sp->sema_type, (uint16_t *)&type);
2199 	suword16_noerr(&sp->sema_type, type);
2200 	if (!get_lwpchan(curproc->p_as, (caddr_t)sp, type,
2201 	    &lwpchan, LWPCHAN_CVPOOL)) {
2202 		error = EFAULT;
2203 		goto out;
2204 	}
2205 	lwpchan_lock(&lwpchan, LWPCHAN_CVPOOL);
2206 	locked = 1;
2207 	fuword32_noerr(&sp->sema_count, (uint32_t *)&count);
2208 	if (count == _SEM_VALUE_MAX)
2209 		error = EOVERFLOW;
2210 	else
2211 		suword32_noerr(&sp->sema_count, ++count);
2212 	if (count == 1) {
2213 		fuword8_noerr(&sp->sema_waiters, &waiters);
2214 		if (waiters) {
2215 			(void) lwp_release(&lwpchan, &waiters, T_WAITCVSEM);
2216 			suword8_noerr(&sp->sema_waiters, waiters);
2217 		}
2218 	}
2219 	lwpchan_unlock(&lwpchan, LWPCHAN_CVPOOL);
2220 out:
2221 	no_fault();
2222 	if (watched)
2223 		watch_enable_addr((caddr_t)sp, sizeof (*sp), S_WRITE);
2224 	if (error)
2225 		return (set_errno(error));
2226 	return (0);
2227 }
2228 
2229 #define	TRW_WANT_WRITE		0x1
2230 #define	TRW_LOCK_GRANTED	0x2
2231 
2232 #define	READ_LOCK		0
2233 #define	WRITE_LOCK		1
2234 #define	TRY_FLAG		0x10
2235 #define	READ_LOCK_TRY		(READ_LOCK | TRY_FLAG)
2236 #define	WRITE_LOCK_TRY		(WRITE_LOCK | TRY_FLAG)
2237 
2238 /*
2239  * Release one writer or one or more readers. Compute the rwstate word to
2240  * reflect the new state of the queue. For a safe hand-off we copy the new
2241  * rwstate value back to userland before we wake any of the new lock holders.
2242  *
2243  * Note that sleepq_insert() implements a prioritized FIFO (with writers
2244  * being given precedence over readers of the same priority).
2245  *
2246  * If the first thread is a reader we scan the queue releasing all readers
2247  * until we hit a writer or the end of the queue. If the first thread is a
2248  * writer we still need to check for another writer.
2249  */
2250 void
lwp_rwlock_release(lwpchan_t * lwpchan,lwp_rwlock_t * rw)2251 lwp_rwlock_release(lwpchan_t *lwpchan, lwp_rwlock_t *rw)
2252 {
2253 	sleepq_head_t *sqh;
2254 	kthread_t *tp;
2255 	kthread_t **tpp;
2256 	kthread_t *tpnext;
2257 	kthread_t *wakelist = NULL;
2258 	uint32_t rwstate = 0;
2259 	int wcount = 0;
2260 	int rcount = 0;
2261 
2262 	sqh = lwpsqhash(lwpchan);
2263 	disp_lock_enter(&sqh->sq_lock);
2264 	tpp = &sqh->sq_queue.sq_first;
2265 	while ((tp = *tpp) != NULL) {
2266 		if (tp->t_lwpchan.lc_wchan0 == lwpchan->lc_wchan0 &&
2267 		    tp->t_lwpchan.lc_wchan == lwpchan->lc_wchan) {
2268 			if (tp->t_writer & TRW_WANT_WRITE) {
2269 				if ((wcount++ == 0) && (rcount == 0)) {
2270 					rwstate |= URW_WRITE_LOCKED;
2271 
2272 					/* Just one writer to wake. */
2273 					sleepq_unlink(tpp, tp);
2274 					wakelist = tp;
2275 
2276 					/* tpp already set for next thread. */
2277 					continue;
2278 				} else {
2279 					rwstate |= URW_HAS_WAITERS;
2280 					/* We need look no further. */
2281 					break;
2282 				}
2283 			} else {
2284 				rcount++;
2285 				if (wcount == 0) {
2286 					rwstate++;
2287 
2288 					/* Add reader to wake list. */
2289 					sleepq_unlink(tpp, tp);
2290 					tp->t_link = wakelist;
2291 					wakelist = tp;
2292 
2293 					/* tpp already set for next thread. */
2294 					continue;
2295 				} else {
2296 					rwstate |= URW_HAS_WAITERS;
2297 					/* We need look no further. */
2298 					break;
2299 				}
2300 			}
2301 		}
2302 		tpp = &tp->t_link;
2303 	}
2304 
2305 	/* Copy the new rwstate back to userland. */
2306 	suword32_noerr(&rw->rwlock_readers, rwstate);
2307 
2308 	/* Wake the new lock holder(s) up. */
2309 	tp = wakelist;
2310 	while (tp != NULL) {
2311 		DTRACE_SCHED1(wakeup, kthread_t *, tp);
2312 		tp->t_wchan0 = NULL;
2313 		tp->t_wchan = NULL;
2314 		tp->t_sobj_ops = NULL;
2315 		tp->t_writer |= TRW_LOCK_GRANTED;
2316 		tpnext = tp->t_link;
2317 		tp->t_link = NULL;
2318 		CL_WAKEUP(tp);
2319 		thread_unlock_high(tp);
2320 		tp = tpnext;
2321 	}
2322 
2323 	disp_lock_exit(&sqh->sq_lock);
2324 }
2325 
2326 /*
2327  * We enter here holding the user-level mutex, which we must release before
2328  * returning or blocking. Based on lwp_cond_wait().
2329  */
2330 static int
lwp_rwlock_lock(lwp_rwlock_t * rw,timespec_t * tsp,int rd_wr)2331 lwp_rwlock_lock(lwp_rwlock_t *rw, timespec_t *tsp, int rd_wr)
2332 {
2333 	lwp_mutex_t *mp = NULL;
2334 	kthread_t *t = curthread;
2335 	kthread_t *tp;
2336 	klwp_t *lwp = ttolwp(t);
2337 	proc_t *p = ttoproc(t);
2338 	lwp_timer_t lwpt;
2339 	lwpchan_t lwpchan;
2340 	lwpchan_t mlwpchan;
2341 	caddr_t timedwait;
2342 	volatile uint16_t type = 0;
2343 	volatile uint8_t mtype = 0;
2344 	uchar_t mwaiters;
2345 	volatile int error = 0;
2346 	int time_error;
2347 	clock_t tim = -1;
2348 	volatile int locked = 0;
2349 	volatile int mlocked = 0;
2350 	volatile int watched = 0;
2351 	volatile int mwatched = 0;
2352 	label_t ljb;
2353 	volatile int no_lwpchan = 1;
2354 	int imm_timeout = 0;
2355 	int try_flag;
2356 	uint32_t rwstate;
2357 	int acquired = 0;
2358 
2359 	/* We only check rw because the mutex is included in it. */
2360 	if ((caddr_t)rw >= p->p_as->a_userlimit)
2361 		return (set_errno(EFAULT));
2362 
2363 	/*
2364 	 * Put the lwp in an orderly state for debugging,
2365 	 * in case we are stopped while sleeping, below.
2366 	 */
2367 	prstop(PR_REQUESTED, 0);
2368 
2369 	/* We must only report this error if we are about to sleep (later). */
2370 	timedwait = (caddr_t)tsp;
2371 	if ((time_error = lwp_timer_copyin(&lwpt, tsp)) == 0 &&
2372 	    lwpt.lwpt_imm_timeout) {
2373 		imm_timeout = 1;
2374 		timedwait = NULL;
2375 	}
2376 
2377 	(void) new_mstate(t, LMS_USER_LOCK);
2378 
2379 	if (on_fault(&ljb)) {
2380 		if (no_lwpchan) {
2381 			error = EFAULT;
2382 			goto out_nodrop;
2383 		}
2384 		if (mlocked) {
2385 			mlocked = 0;
2386 			lwpchan_unlock(&mlwpchan, LWPCHAN_MPPOOL);
2387 		}
2388 		if (locked) {
2389 			locked = 0;
2390 			lwpchan_unlock(&lwpchan, LWPCHAN_CVPOOL);
2391 		}
2392 		/*
2393 		 * Set up another on_fault() for a possible fault
2394 		 * on the user lock accessed at "out_drop".
2395 		 */
2396 		if (on_fault(&ljb)) {
2397 			if (mlocked) {
2398 				mlocked = 0;
2399 				lwpchan_unlock(&mlwpchan, LWPCHAN_MPPOOL);
2400 			}
2401 			error = EFAULT;
2402 			goto out_nodrop;
2403 		}
2404 		error = EFAULT;
2405 		goto out_nodrop;
2406 	}
2407 
2408 	/* Process rd_wr (including sanity check). */
2409 	try_flag = (rd_wr & TRY_FLAG);
2410 	rd_wr &= ~TRY_FLAG;
2411 	if ((rd_wr != READ_LOCK) && (rd_wr != WRITE_LOCK)) {
2412 		error = EINVAL;
2413 		goto out_nodrop;
2414 	}
2415 
2416 	/*
2417 	 * Force Copy-on-write if necessary and ensure that the
2418 	 * synchronization object resides in read/write memory.
2419 	 * Cause an EFAULT return now if this is not so.
2420 	 */
2421 	mp = &rw->mutex;
2422 	fuword8_noerr(&mp->mutex_type, (uint8_t *)&mtype);
2423 	fuword16_noerr(&rw->rwlock_type, (uint16_t *)&type);
2424 	suword8_noerr(&mp->mutex_type, mtype);
2425 	suword16_noerr(&rw->rwlock_type, type);
2426 
2427 	/* We can only continue for simple USYNC_PROCESS locks. */
2428 	if ((mtype != USYNC_PROCESS) || (type != USYNC_PROCESS)) {
2429 		error = EINVAL;
2430 		goto out_nodrop;
2431 	}
2432 
2433 	/* Convert user level mutex, "mp", to a unique lwpchan. */
2434 	if (!get_lwpchan(p->p_as, (caddr_t)mp, mtype,
2435 	    &mlwpchan, LWPCHAN_MPPOOL)) {
2436 		error = EFAULT;
2437 		goto out_nodrop;
2438 	}
2439 
2440 	/* Convert user level rwlock, "rw", to a unique lwpchan. */
2441 	if (!get_lwpchan(p->p_as, (caddr_t)rw, type,
2442 	    &lwpchan, LWPCHAN_CVPOOL)) {
2443 		error = EFAULT;
2444 		goto out_nodrop;
2445 	}
2446 
2447 	no_lwpchan = 0;
2448 	watched = watch_disable_addr((caddr_t)rw, sizeof (*rw), S_WRITE);
2449 	mwatched = watch_disable_addr((caddr_t)mp, sizeof (*mp), S_WRITE);
2450 
2451 	/*
2452 	 * lwpchan_lock() ensures that the calling LWP is put to sleep
2453 	 * atomically with respect to a possible wakeup which is a result
2454 	 * of lwp_rwlock_unlock().
2455 	 *
2456 	 * What's misleading is that the LWP is put to sleep after the
2457 	 * rwlock's mutex is released. This is OK as long as the release
2458 	 * operation is also done while holding mlwpchan. The LWP is then
2459 	 * put to sleep when the possibility of pagefaulting or sleeping
2460 	 * has been completely eliminated.
2461 	 */
2462 	lwpchan_lock(&lwpchan, LWPCHAN_CVPOOL);
2463 	locked = 1;
2464 	lwpchan_lock(&mlwpchan, LWPCHAN_MPPOOL);
2465 	mlocked = 1;
2466 
2467 	/*
2468 	 * Fetch the current rwlock state.
2469 	 *
2470 	 * The possibility of spurious wake-ups or killed waiters means
2471 	 * rwstate's URW_HAS_WAITERS bit may indicate false positives.
2472 	 * We only fix these if they are important to us.
2473 	 *
2474 	 * Although various error states can be observed here (e.g. the lock
2475 	 * is not held, but there are waiters) we assume these are applicaton
2476 	 * errors and so we take no corrective action.
2477 	 */
2478 	fuword32_noerr(&rw->rwlock_readers, &rwstate);
2479 	/*
2480 	 * We cannot legitimately get here from user-level
2481 	 * without URW_HAS_WAITERS being set.
2482 	 * Set it now to guard against user-level error.
2483 	 */
2484 	rwstate |= URW_HAS_WAITERS;
2485 
2486 	/*
2487 	 * We can try only if the lock isn't held by a writer.
2488 	 */
2489 	if (!(rwstate & URW_WRITE_LOCKED)) {
2490 		tp = lwp_queue_waiter(&lwpchan);
2491 		if (tp == NULL) {
2492 			/*
2493 			 * Hmmm, rwstate indicates waiters but there are
2494 			 * none queued. This could just be the result of a
2495 			 * spurious wakeup, so let's ignore it.
2496 			 *
2497 			 * We now have a chance to acquire the lock
2498 			 * uncontended, but this is the last chance for
2499 			 * a writer to acquire the lock without blocking.
2500 			 */
2501 			if (rd_wr == READ_LOCK) {
2502 				rwstate++;
2503 				acquired = 1;
2504 			} else if ((rwstate & URW_READERS_MASK) == 0) {
2505 				rwstate |= URW_WRITE_LOCKED;
2506 				acquired = 1;
2507 			}
2508 		} else if (rd_wr == READ_LOCK) {
2509 			/*
2510 			 * This is the last chance for a reader to acquire
2511 			 * the lock now, but it can only do so if there is
2512 			 * no writer of equal or greater priority at the
2513 			 * head of the queue .
2514 			 *
2515 			 * It is also just possible that there is a reader
2516 			 * at the head of the queue. This may be the result
2517 			 * of a spurious wakeup or an application failure.
2518 			 * In this case we only acquire the lock if we have
2519 			 * equal or greater priority. It is not our job to
2520 			 * release spurious waiters.
2521 			 */
2522 			pri_t our_pri = DISP_PRIO(t);
2523 			pri_t his_pri = DISP_PRIO(tp);
2524 
2525 			if ((our_pri > his_pri) || ((our_pri == his_pri) &&
2526 			    !(tp->t_writer & TRW_WANT_WRITE))) {
2527 				rwstate++;
2528 				acquired = 1;
2529 			}
2530 		}
2531 	}
2532 
2533 	if (acquired || try_flag || time_error) {
2534 		/*
2535 		 * We're not going to block this time.
2536 		 */
2537 		suword32_noerr(&rw->rwlock_readers, rwstate);
2538 		lwpchan_unlock(&lwpchan, LWPCHAN_CVPOOL);
2539 		locked = 0;
2540 
2541 		if (acquired) {
2542 			/*
2543 			 * Got the lock!
2544 			 */
2545 			error = 0;
2546 
2547 		} else if (try_flag) {
2548 			/*
2549 			 * We didn't get the lock and we're about to block.
2550 			 * If we're doing a trylock, return EBUSY instead.
2551 			 */
2552 			error = EBUSY;
2553 
2554 		} else if (time_error) {
2555 			/*
2556 			 * The SUSV3 POSIX spec is very clear that we should
2557 			 * get no error from validating the timer (above)
2558 			 * until we would actually sleep.
2559 			 */
2560 			error = time_error;
2561 		}
2562 
2563 		goto out_drop;
2564 	}
2565 
2566 	/*
2567 	 * We're about to block, so indicate what kind of waiter we are.
2568 	 */
2569 	t->t_writer = 0;
2570 	if (rd_wr == WRITE_LOCK)
2571 		t->t_writer = TRW_WANT_WRITE;
2572 	suword32_noerr(&rw->rwlock_readers, rwstate);
2573 
2574 	/*
2575 	 * Unlock the rwlock's mutex (pagefaults are possible here).
2576 	 */
2577 	set_owner_pid(mp, 0, 0);
2578 	ulock_clear(&mp->mutex_lockw);
2579 	fuword8_noerr(&mp->mutex_waiters, &mwaiters);
2580 	if (mwaiters != 0) {
2581 		/*
2582 		 * Given the locking of mlwpchan around the release of
2583 		 * the mutex and checking for waiters, the following
2584 		 * call to lwp_release() can fail ONLY if the lock
2585 		 * acquirer is interrupted after setting the waiter bit,
2586 		 * calling lwp_block() and releasing mlwpchan.
2587 		 * In this case, it could get pulled off the LWP sleep
2588 		 * queue (via setrun()) before the following call to
2589 		 * lwp_release() occurs, and the lock requestor will
2590 		 * update the waiter bit correctly by re-evaluating it.
2591 		 */
2592 		if (lwp_release(&mlwpchan, &mwaiters, 0))
2593 			suword8_noerr(&mp->mutex_waiters, mwaiters);
2594 	}
2595 	lwpchan_unlock(&mlwpchan, LWPCHAN_MPPOOL);
2596 	mlocked = 0;
2597 	no_fault();
2598 
2599 	if (mwatched) {
2600 		watch_enable_addr((caddr_t)mp, sizeof (*mp), S_WRITE);
2601 		mwatched = 0;
2602 	}
2603 	if (watched) {
2604 		watch_enable_addr((caddr_t)rw, sizeof (*rw), S_WRITE);
2605 		watched = 0;
2606 	}
2607 
2608 	if (timedwait) {
2609 		/*
2610 		 * If we successfully queue the timeout,
2611 		 * then don't drop t_delay_lock until
2612 		 * we are on the sleep queue (below).
2613 		 */
2614 		mutex_enter(&t->t_delay_lock);
2615 		if (lwp_timer_enqueue(&lwpt) != 0) {
2616 			mutex_exit(&t->t_delay_lock);
2617 			imm_timeout = 1;
2618 			timedwait = NULL;
2619 		}
2620 	}
2621 	t->t_flag |= T_WAITCVSEM;
2622 	lwp_block(&lwpchan);
2623 
2624 	/*
2625 	 * Nothing should happen to cause the LWp to go to sleep until after
2626 	 * it returns from swtch().
2627 	 */
2628 	if (timedwait)
2629 		mutex_exit(&t->t_delay_lock);
2630 	locked = 0;
2631 	lwpchan_unlock(&lwpchan, LWPCHAN_CVPOOL);
2632 	if (ISSIG(t, JUSTLOOKING) || MUSTRETURN(p, t) || imm_timeout)
2633 		setrun(t);
2634 	swtch();
2635 
2636 	/*
2637 	 * We're back, but we need to work out why. Were we interrupted? Did
2638 	 * we timeout? Were we granted the lock?
2639 	 */
2640 	error = EAGAIN;
2641 	acquired = (t->t_writer & TRW_LOCK_GRANTED);
2642 	t->t_writer = 0;
2643 	t->t_flag &= ~(T_WAITCVSEM | T_WAKEABLE);
2644 	if (timedwait)
2645 		tim = lwp_timer_dequeue(&lwpt);
2646 	if (ISSIG(t, FORREAL) || lwp->lwp_sysabort || MUSTRETURN(p, t))
2647 		error = EINTR;
2648 	else if (imm_timeout || (timedwait && tim == -1))
2649 		error = ETIME;
2650 	lwp->lwp_asleep = 0;
2651 	lwp->lwp_sysabort = 0;
2652 	setallwatch();
2653 
2654 	/*
2655 	 * If we were granted the lock we don't care about EINTR or ETIME.
2656 	 */
2657 	if (acquired)
2658 		error = 0;
2659 
2660 	if (t->t_mstate == LMS_USER_LOCK)
2661 		(void) new_mstate(t, LMS_SYSTEM);
2662 
2663 	if (error)
2664 		return (set_errno(error));
2665 	return (0);
2666 
2667 out_drop:
2668 	/*
2669 	 * Make sure that the user level lock is dropped before returning
2670 	 * to the caller.
2671 	 */
2672 	if (!mlocked) {
2673 		lwpchan_lock(&mlwpchan, LWPCHAN_MPPOOL);
2674 		mlocked = 1;
2675 	}
2676 	set_owner_pid(mp, 0, 0);
2677 	ulock_clear(&mp->mutex_lockw);
2678 	fuword8_noerr(&mp->mutex_waiters, &mwaiters);
2679 	if (mwaiters != 0) {
2680 		/*
2681 		 * See comment above on lock clearing and lwp_release()
2682 		 * success/failure.
2683 		 */
2684 		if (lwp_release(&mlwpchan, &mwaiters, 0))
2685 			suword8_noerr(&mp->mutex_waiters, mwaiters);
2686 	}
2687 	lwpchan_unlock(&mlwpchan, LWPCHAN_MPPOOL);
2688 	mlocked = 0;
2689 
2690 out_nodrop:
2691 	no_fault();
2692 	if (mwatched)
2693 		watch_enable_addr((caddr_t)mp, sizeof (*mp), S_WRITE);
2694 	if (watched)
2695 		watch_enable_addr((caddr_t)rw, sizeof (*rw), S_WRITE);
2696 	if (t->t_mstate == LMS_USER_LOCK)
2697 		(void) new_mstate(t, LMS_SYSTEM);
2698 	if (error)
2699 		return (set_errno(error));
2700 	return (0);
2701 }
2702 
2703 /*
2704  * We enter here holding the user-level mutex but, unlike lwp_rwlock_lock(),
2705  * we never drop the lock.
2706  */
2707 static int
lwp_rwlock_unlock(lwp_rwlock_t * rw)2708 lwp_rwlock_unlock(lwp_rwlock_t *rw)
2709 {
2710 	kthread_t *t = curthread;
2711 	proc_t *p = ttoproc(t);
2712 	lwpchan_t lwpchan;
2713 	volatile uint16_t type = 0;
2714 	volatile int error = 0;
2715 	volatile int locked = 0;
2716 	volatile int watched = 0;
2717 	label_t ljb;
2718 	volatile int no_lwpchan = 1;
2719 	uint32_t rwstate;
2720 
2721 	/* We only check rw because the mutex is included in it. */
2722 	if ((caddr_t)rw >= p->p_as->a_userlimit)
2723 		return (set_errno(EFAULT));
2724 
2725 	if (on_fault(&ljb)) {
2726 		if (no_lwpchan) {
2727 			error = EFAULT;
2728 			goto out_nodrop;
2729 		}
2730 		if (locked) {
2731 			locked = 0;
2732 			lwpchan_unlock(&lwpchan, LWPCHAN_CVPOOL);
2733 		}
2734 		error = EFAULT;
2735 		goto out_nodrop;
2736 	}
2737 
2738 	/*
2739 	 * Force Copy-on-write if necessary and ensure that the
2740 	 * synchronization object resides in read/write memory.
2741 	 * Cause an EFAULT return now if this is not so.
2742 	 */
2743 	fuword16_noerr(&rw->rwlock_type, (uint16_t *)&type);
2744 	suword16_noerr(&rw->rwlock_type, type);
2745 
2746 	/* We can only continue for simple USYNC_PROCESS locks. */
2747 	if (type != USYNC_PROCESS) {
2748 		error = EINVAL;
2749 		goto out_nodrop;
2750 	}
2751 
2752 	/* Convert user level rwlock, "rw", to a unique lwpchan. */
2753 	if (!get_lwpchan(p->p_as, (caddr_t)rw, type,
2754 	    &lwpchan, LWPCHAN_CVPOOL)) {
2755 		error = EFAULT;
2756 		goto out_nodrop;
2757 	}
2758 
2759 	no_lwpchan = 0;
2760 	watched = watch_disable_addr((caddr_t)rw, sizeof (*rw), S_WRITE);
2761 
2762 	lwpchan_lock(&lwpchan, LWPCHAN_CVPOOL);
2763 	locked = 1;
2764 
2765 	/*
2766 	 * We can resolve multiple readers (except the last reader) here.
2767 	 * For the last reader or a writer we need lwp_rwlock_release(),
2768 	 * to which we also delegate the task of copying the new rwstate
2769 	 * back to userland (see the comment there).
2770 	 */
2771 	fuword32_noerr(&rw->rwlock_readers, &rwstate);
2772 	if (rwstate & URW_WRITE_LOCKED)
2773 		lwp_rwlock_release(&lwpchan, rw);
2774 	else if ((rwstate & URW_READERS_MASK) > 0) {
2775 		rwstate--;
2776 		if ((rwstate & URW_READERS_MASK) == 0)
2777 			lwp_rwlock_release(&lwpchan, rw);
2778 		else
2779 			suword32_noerr(&rw->rwlock_readers, rwstate);
2780 	}
2781 
2782 	lwpchan_unlock(&lwpchan, LWPCHAN_CVPOOL);
2783 	locked = 0;
2784 	error = 0;
2785 
2786 out_nodrop:
2787 	no_fault();
2788 	if (watched)
2789 		watch_enable_addr((caddr_t)rw, sizeof (*rw), S_WRITE);
2790 	if (error)
2791 		return (set_errno(error));
2792 	return (0);
2793 }
2794 
2795 int
lwp_rwlock_sys(int subcode,lwp_rwlock_t * rwlp,timespec_t * tsp)2796 lwp_rwlock_sys(int subcode, lwp_rwlock_t *rwlp, timespec_t *tsp)
2797 {
2798 	switch (subcode) {
2799 	case 0:
2800 		return (lwp_rwlock_lock(rwlp, tsp, READ_LOCK));
2801 	case 1:
2802 		return (lwp_rwlock_lock(rwlp, tsp, WRITE_LOCK));
2803 	case 2:
2804 		return (lwp_rwlock_lock(rwlp, NULL, READ_LOCK_TRY));
2805 	case 3:
2806 		return (lwp_rwlock_lock(rwlp, NULL, WRITE_LOCK_TRY));
2807 	case 4:
2808 		return (lwp_rwlock_unlock(rwlp));
2809 	}
2810 	return (set_errno(EINVAL));
2811 }
2812 
2813 /*
2814  * Return the owner of the user-level s-object.
2815  * Since we can't really do this, return NULL.
2816  */
2817 /* ARGSUSED */
2818 static kthread_t *
lwpsobj_owner(caddr_t sobj)2819 lwpsobj_owner(caddr_t sobj)
2820 {
2821 	return ((kthread_t *)NULL);
2822 }
2823 
2824 /*
2825  * Wake up a thread asleep on a user-level synchronization
2826  * object.
2827  */
2828 static void
lwp_unsleep(kthread_t * t)2829 lwp_unsleep(kthread_t *t)
2830 {
2831 	ASSERT(THREAD_LOCK_HELD(t));
2832 	if (t->t_wchan0 != NULL) {
2833 		sleepq_head_t *sqh;
2834 		sleepq_t *sqp = t->t_sleepq;
2835 
2836 		if (sqp != NULL) {
2837 			sqh = lwpsqhash(&t->t_lwpchan);
2838 			ASSERT(&sqh->sq_queue == sqp);
2839 			sleepq_unsleep(t);
2840 			disp_lock_exit_high(&sqh->sq_lock);
2841 			CL_SETRUN(t);
2842 			return;
2843 		}
2844 	}
2845 	panic("lwp_unsleep: thread %p not on sleepq", (void *)t);
2846 }
2847 
2848 /*
2849  * Change the priority of a thread asleep on a user-level
2850  * synchronization object. To maintain proper priority order,
2851  * we:
2852  *	o dequeue the thread.
2853  *	o change its priority.
2854  *	o re-enqueue the thread.
2855  * Assumption: the thread is locked on entry.
2856  */
2857 static void
lwp_change_pri(kthread_t * t,pri_t pri,pri_t * t_prip)2858 lwp_change_pri(kthread_t *t, pri_t pri, pri_t *t_prip)
2859 {
2860 	ASSERT(THREAD_LOCK_HELD(t));
2861 	if (t->t_wchan0 != NULL) {
2862 		sleepq_t   *sqp = t->t_sleepq;
2863 
2864 		sleepq_dequeue(t);
2865 		*t_prip = pri;
2866 		sleepq_insert(sqp, t);
2867 	} else
2868 		panic("lwp_change_pri: %p not on a sleep queue", (void *)t);
2869 }
2870 
2871 /*
2872  * Clean up a left-over process-shared robust mutex
2873  */
2874 static void
lwp_mutex_cleanup(lwpchan_entry_t * ent,uint16_t lockflg)2875 lwp_mutex_cleanup(lwpchan_entry_t *ent, uint16_t lockflg)
2876 {
2877 	uint16_t flag;
2878 	uchar_t waiters;
2879 	label_t ljb;
2880 	pid_t owner_pid;
2881 	lwp_mutex_t *lp;
2882 	volatile int locked = 0;
2883 	volatile int watched = 0;
2884 	volatile struct upimutex *upimutex = NULL;
2885 	volatile int upilocked = 0;
2886 
2887 	if ((ent->lwpchan_type & (USYNC_PROCESS | LOCK_ROBUST))
2888 	    != (USYNC_PROCESS | LOCK_ROBUST))
2889 		return;
2890 
2891 	lp = (lwp_mutex_t *)ent->lwpchan_addr;
2892 	watched = watch_disable_addr((caddr_t)lp, sizeof (*lp), S_WRITE);
2893 	if (on_fault(&ljb)) {
2894 		if (locked)
2895 			lwpchan_unlock(&ent->lwpchan_lwpchan, LWPCHAN_MPPOOL);
2896 		if (upilocked)
2897 			upimutex_unlock((upimutex_t *)upimutex, 0);
2898 		goto out;
2899 	}
2900 
2901 	fuword32_noerr(&lp->mutex_ownerpid, (uint32_t *)&owner_pid);
2902 
2903 	if (UPIMUTEX(ent->lwpchan_type)) {
2904 		lwpchan_t lwpchan = ent->lwpchan_lwpchan;
2905 		upib_t *upibp = &UPI_CHAIN(lwpchan);
2906 
2907 		if (owner_pid != curproc->p_pid)
2908 			goto out;
2909 		mutex_enter(&upibp->upib_lock);
2910 		upimutex = upi_get(upibp, &lwpchan);
2911 		if (upimutex == NULL || upimutex->upi_owner != curthread) {
2912 			mutex_exit(&upibp->upib_lock);
2913 			goto out;
2914 		}
2915 		mutex_exit(&upibp->upib_lock);
2916 		upilocked = 1;
2917 		flag = lwp_clear_mutex(lp, lockflg);
2918 		suword8_noerr(&lp->mutex_lockw, 0);
2919 		upimutex_unlock((upimutex_t *)upimutex, flag);
2920 	} else {
2921 		lwpchan_lock(&ent->lwpchan_lwpchan, LWPCHAN_MPPOOL);
2922 		locked = 1;
2923 		/*
2924 		 * Clear the spinners count because one of our
2925 		 * threads could have been spinning for this lock
2926 		 * at user level when the process was suddenly killed.
2927 		 * There is no harm in this since user-level libc code
2928 		 * will adapt to the sudden change in the spinner count.
2929 		 */
2930 		suword8_noerr(&lp->mutex_spinners, 0);
2931 		if (owner_pid != curproc->p_pid) {
2932 			/*
2933 			 * We are not the owner.  There may or may not be one.
2934 			 * If there are waiters, we wake up one or all of them.
2935 			 * It doesn't hurt to wake them up in error since
2936 			 * they will just retry the lock and go to sleep
2937 			 * again if necessary.
2938 			 */
2939 			fuword8_noerr(&lp->mutex_waiters, &waiters);
2940 			if (waiters != 0) {	/* there are waiters */
2941 				fuword16_noerr(&lp->mutex_flag, &flag);
2942 				if (flag & LOCK_NOTRECOVERABLE) {
2943 					lwp_release_all(&ent->lwpchan_lwpchan);
2944 					suword8_noerr(&lp->mutex_waiters, 0);
2945 				} else if (lwp_release(&ent->lwpchan_lwpchan,
2946 				    &waiters, 0)) {
2947 					suword8_noerr(&lp->mutex_waiters,
2948 					    waiters);
2949 				}
2950 			}
2951 		} else {
2952 			/*
2953 			 * We are the owner.  Release it.
2954 			 */
2955 			(void) lwp_clear_mutex(lp, lockflg);
2956 			ulock_clear(&lp->mutex_lockw);
2957 			fuword8_noerr(&lp->mutex_waiters, &waiters);
2958 			if (waiters &&
2959 			    lwp_release(&ent->lwpchan_lwpchan, &waiters, 0))
2960 				suword8_noerr(&lp->mutex_waiters, waiters);
2961 		}
2962 		lwpchan_unlock(&ent->lwpchan_lwpchan, LWPCHAN_MPPOOL);
2963 	}
2964 out:
2965 	no_fault();
2966 	if (watched)
2967 		watch_enable_addr((caddr_t)lp, sizeof (*lp), S_WRITE);
2968 }
2969 
2970 /*
2971  * Register a process-shared robust mutex in the lwpchan cache.
2972  */
2973 int
lwp_mutex_register(lwp_mutex_t * lp,caddr_t uaddr)2974 lwp_mutex_register(lwp_mutex_t *lp, caddr_t uaddr)
2975 {
2976 	int error = 0;
2977 	volatile int watched;
2978 	label_t ljb;
2979 	uint8_t type;
2980 	lwpchan_t lwpchan;
2981 
2982 	if ((caddr_t)lp >= (caddr_t)USERLIMIT)
2983 		return (set_errno(EFAULT));
2984 
2985 	watched = watch_disable_addr((caddr_t)lp, sizeof (*lp), S_WRITE);
2986 
2987 	if (on_fault(&ljb)) {
2988 		error = EFAULT;
2989 	} else {
2990 		/*
2991 		 * Force Copy-on-write if necessary and ensure that the
2992 		 * synchronization object resides in read/write memory.
2993 		 * Cause an EFAULT return now if this is not so.
2994 		 */
2995 		fuword8_noerr(&lp->mutex_type, &type);
2996 		suword8_noerr(&lp->mutex_type, type);
2997 		if ((type & (USYNC_PROCESS|LOCK_ROBUST))
2998 		    != (USYNC_PROCESS|LOCK_ROBUST)) {
2999 			error = EINVAL;
3000 		} else if (!lwpchan_get_mapping(curproc->p_as, (caddr_t)lp,
3001 		    uaddr, type, &lwpchan, LWPCHAN_MPPOOL)) {
3002 			error = EFAULT;
3003 		}
3004 	}
3005 	no_fault();
3006 	if (watched)
3007 		watch_enable_addr((caddr_t)lp, sizeof (*lp), S_WRITE);
3008 	if (error)
3009 		return (set_errno(error));
3010 	return (0);
3011 }
3012 
3013 /*
3014  * There is a user-level robust lock registration in libc.
3015  * Mark it as invalid by storing -1 into the location of the pointer.
3016  */
3017 static void
lwp_mutex_unregister(void * uaddr)3018 lwp_mutex_unregister(void *uaddr)
3019 {
3020 	if (get_udatamodel() == DATAMODEL_NATIVE) {
3021 		(void) sulword(uaddr, (ulong_t)-1);
3022 #ifdef _SYSCALL32_IMPL
3023 	} else {
3024 		(void) suword32(uaddr, (uint32_t)-1);
3025 #endif
3026 	}
3027 }
3028 
3029 int
lwp_mutex_trylock(lwp_mutex_t * lp,uintptr_t owner)3030 lwp_mutex_trylock(lwp_mutex_t *lp, uintptr_t owner)
3031 {
3032 	kthread_t *t = curthread;
3033 	proc_t *p = ttoproc(t);
3034 	int error = 0;
3035 	volatile int locked = 0;
3036 	volatile int watched = 0;
3037 	label_t ljb;
3038 	volatile uint8_t type = 0;
3039 	uint16_t flag;
3040 	lwpchan_t lwpchan;
3041 
3042 	if ((caddr_t)lp >= p->p_as->a_userlimit)
3043 		return (set_errno(EFAULT));
3044 
3045 	(void) new_mstate(t, LMS_USER_LOCK);
3046 
3047 	if (on_fault(&ljb)) {
3048 		if (locked)
3049 			lwpchan_unlock(&lwpchan, LWPCHAN_MPPOOL);
3050 		error = EFAULT;
3051 		goto out;
3052 	}
3053 	/*
3054 	 * Force Copy-on-write if necessary and ensure that the
3055 	 * synchronization object resides in read/write memory.
3056 	 * Cause an EFAULT return now if this is not so.
3057 	 */
3058 	fuword8_noerr(&lp->mutex_type, (uint8_t *)&type);
3059 	suword8_noerr(&lp->mutex_type, type);
3060 	if (UPIMUTEX(type)) {
3061 		no_fault();
3062 		error = lwp_upimutex_lock(lp, type, UPIMUTEX_TRY, NULL);
3063 		if (error == 0 || error == EOWNERDEAD ||
3064 		    error == ELOCKUNMAPPED) {
3065 			volatile int locked = error != 0;
3066 			if (on_fault(&ljb)) {
3067 				if (locked != 0)
3068 					error = lwp_upimutex_unlock(lp, type);
3069 				else
3070 					error = EFAULT;
3071 				goto upierr;
3072 			}
3073 			set_owner_pid(lp, owner,
3074 			    (type & USYNC_PROCESS)? p->p_pid : 0);
3075 			no_fault();
3076 		}
3077 
3078 upierr:
3079 		if (error)
3080 			return (set_errno(error));
3081 		return (0);
3082 	}
3083 	if (!get_lwpchan(curproc->p_as, (caddr_t)lp, type,
3084 	    &lwpchan, LWPCHAN_MPPOOL)) {
3085 		error = EFAULT;
3086 		goto out;
3087 	}
3088 	lwpchan_lock(&lwpchan, LWPCHAN_MPPOOL);
3089 	locked = 1;
3090 	if (type & LOCK_ROBUST) {
3091 		fuword16_noerr(&lp->mutex_flag, &flag);
3092 		if (flag & LOCK_NOTRECOVERABLE) {
3093 			lwpchan_unlock(&lwpchan, LWPCHAN_MPPOOL);
3094 			error =  ENOTRECOVERABLE;
3095 			goto out;
3096 		}
3097 	}
3098 
3099 	watched = watch_disable_addr((caddr_t)lp, sizeof (*lp), S_WRITE);
3100 
3101 	if (!ulock_try(&lp->mutex_lockw))
3102 		error = EBUSY;
3103 	else {
3104 		set_owner_pid(lp, owner, (type & USYNC_PROCESS)? p->p_pid : 0);
3105 		if (type & LOCK_ROBUST) {
3106 			fuword16_noerr(&lp->mutex_flag, &flag);
3107 			if (flag & (LOCK_OWNERDEAD | LOCK_UNMAPPED)) {
3108 				if (flag & LOCK_OWNERDEAD)
3109 					error = EOWNERDEAD;
3110 				else if (type & USYNC_PROCESS_ROBUST)
3111 					error = ELOCKUNMAPPED;
3112 				else
3113 					error = EOWNERDEAD;
3114 			}
3115 		}
3116 	}
3117 	locked = 0;
3118 	lwpchan_unlock(&lwpchan, LWPCHAN_MPPOOL);
3119 out:
3120 
3121 	if (t->t_mstate == LMS_USER_LOCK)
3122 		(void) new_mstate(t, LMS_SYSTEM);
3123 
3124 	no_fault();
3125 	if (watched)
3126 		watch_enable_addr((caddr_t)lp, sizeof (*lp), S_WRITE);
3127 	if (error)
3128 		return (set_errno(error));
3129 	return (0);
3130 }
3131 
3132 /*
3133  * unlock the mutex and unblock lwps that is trying to acquire this mutex.
3134  * the blocked lwp resumes and retries to acquire the lock.
3135  */
3136 int
lwp_mutex_unlock(lwp_mutex_t * lp)3137 lwp_mutex_unlock(lwp_mutex_t *lp)
3138 {
3139 	proc_t *p = ttoproc(curthread);
3140 	lwpchan_t lwpchan;
3141 	uchar_t waiters;
3142 	volatile int locked = 0;
3143 	volatile int watched = 0;
3144 	volatile uint8_t type = 0;
3145 	label_t ljb;
3146 	uint16_t flag;
3147 	int error = 0;
3148 
3149 	if ((caddr_t)lp >= p->p_as->a_userlimit)
3150 		return (set_errno(EFAULT));
3151 
3152 	if (on_fault(&ljb)) {
3153 		if (locked)
3154 			lwpchan_unlock(&lwpchan, LWPCHAN_MPPOOL);
3155 		error = EFAULT;
3156 		goto out;
3157 	}
3158 
3159 	/*
3160 	 * Force Copy-on-write if necessary and ensure that the
3161 	 * synchronization object resides in read/write memory.
3162 	 * Cause an EFAULT return now if this is not so.
3163 	 */
3164 	fuword8_noerr(&lp->mutex_type, (uint8_t *)&type);
3165 	suword8_noerr(&lp->mutex_type, type);
3166 
3167 	if (UPIMUTEX(type)) {
3168 		no_fault();
3169 		error = lwp_upimutex_unlock(lp, type);
3170 		if (error)
3171 			return (set_errno(error));
3172 		return (0);
3173 	}
3174 
3175 	watched = watch_disable_addr((caddr_t)lp, sizeof (*lp), S_WRITE);
3176 
3177 	if (!get_lwpchan(curproc->p_as, (caddr_t)lp, type,
3178 	    &lwpchan, LWPCHAN_MPPOOL)) {
3179 		error = EFAULT;
3180 		goto out;
3181 	}
3182 	lwpchan_lock(&lwpchan, LWPCHAN_MPPOOL);
3183 	locked = 1;
3184 	if (type & LOCK_ROBUST) {
3185 		fuword16_noerr(&lp->mutex_flag, &flag);
3186 		if (flag & (LOCK_OWNERDEAD | LOCK_UNMAPPED)) {
3187 			flag &= ~(LOCK_OWNERDEAD | LOCK_UNMAPPED);
3188 			flag |= LOCK_NOTRECOVERABLE;
3189 			suword16_noerr(&lp->mutex_flag, flag);
3190 		}
3191 	}
3192 	set_owner_pid(lp, 0, 0);
3193 	ulock_clear(&lp->mutex_lockw);
3194 	/*
3195 	 * Always wake up an lwp (if any) waiting on lwpchan. The woken lwp will
3196 	 * re-try the lock in lwp_mutex_timedlock(). The call to lwp_release()
3197 	 * may fail.  If it fails, do not write into the waiter bit.
3198 	 * The call to lwp_release() might fail due to one of three reasons:
3199 	 *
3200 	 * 	1. due to the thread which set the waiter bit not actually
3201 	 *	   sleeping since it got the lock on the re-try. The waiter
3202 	 *	   bit will then be correctly updated by that thread. This
3203 	 *	   window may be closed by reading the wait bit again here
3204 	 *	   and not calling lwp_release() at all if it is zero.
3205 	 *	2. the thread which set the waiter bit and went to sleep
3206 	 *	   was woken up by a signal. This time, the waiter recomputes
3207 	 *	   the wait bit in the return with EINTR code.
3208 	 *	3. the waiter bit read by lwp_mutex_wakeup() was in
3209 	 *	   memory that has been re-used after the lock was dropped.
3210 	 *	   In this case, writing into the waiter bit would cause data
3211 	 *	   corruption.
3212 	 */
3213 	fuword8_noerr(&lp->mutex_waiters, &waiters);
3214 	if (waiters) {
3215 		if ((type & LOCK_ROBUST) &&
3216 		    (flag & LOCK_NOTRECOVERABLE)) {
3217 			lwp_release_all(&lwpchan);
3218 			suword8_noerr(&lp->mutex_waiters, 0);
3219 		} else if (lwp_release(&lwpchan, &waiters, 0)) {
3220 			suword8_noerr(&lp->mutex_waiters, waiters);
3221 		}
3222 	}
3223 
3224 	lwpchan_unlock(&lwpchan, LWPCHAN_MPPOOL);
3225 out:
3226 	no_fault();
3227 	if (watched)
3228 		watch_enable_addr((caddr_t)lp, sizeof (*lp), S_WRITE);
3229 	if (error)
3230 		return (set_errno(error));
3231 	return (0);
3232 }
3233