1 /* 2 * General MIPS MT support routines, usable in AP/SP, SMVP, or SMTC kernels 3 * Copyright (C) 2005 Mips Technologies, Inc 4 */ 5 #include <linux/cpu.h> 6 #include <linux/cpuset.h> 7 #include <linux/cpumask.h> 8 #include <linux/delay.h> 9 #include <linux/kernel.h> 10 #include <linux/init.h> 11 #include <linux/sched.h> 12 #include <linux/security.h> 13 #include <linux/types.h> 14 #include <asm/uaccess.h> 15 16 /* 17 * CPU mask used to set process affinity for MT VPEs/TCs with FPUs 18 */ 19 cpumask_t mt_fpu_cpumask; 20 21 static int fpaff_threshold = -1; 22 unsigned long mt_fpemul_threshold; 23 24 /* 25 * Replacement functions for the sys_sched_setaffinity() and 26 * sys_sched_getaffinity() system calls, so that we can integrate 27 * FPU affinity with the user's requested processor affinity. 28 * This code is 98% identical with the sys_sched_setaffinity() 29 * and sys_sched_getaffinity() system calls, and should be 30 * updated when kernel/sched/core.c changes. 31 */ 32 33 /* 34 * find_process_by_pid - find a process with a matching PID value. 35 * used in sys_sched_set/getaffinity() in kernel/sched/core.c, so 36 * cloned here. 37 */ 38 static inline struct task_struct *find_process_by_pid(pid_t pid) 39 { 40 return pid ? find_task_by_vpid(pid) : current; 41 } 42 43 /* 44 * check the target process has a UID that matches the current process's 45 */ 46 static bool check_same_owner(struct task_struct *p) 47 { 48 const struct cred *cred = current_cred(), *pcred; 49 bool match; 50 51 rcu_read_lock(); 52 pcred = __task_cred(p); 53 match = (uid_eq(cred->euid, pcred->euid) || 54 uid_eq(cred->euid, pcred->uid)); 55 rcu_read_unlock(); 56 return match; 57 } 58 59 /* 60 * mipsmt_sys_sched_setaffinity - set the cpu affinity of a process 61 */ 62 asmlinkage long mipsmt_sys_sched_setaffinity(pid_t pid, unsigned int len, 63 unsigned long __user *user_mask_ptr) 64 { 65 cpumask_var_t cpus_allowed, new_mask, effective_mask; 66 struct thread_info *ti; 67 struct task_struct *p; 68 int retval; 69 70 if (len < sizeof(new_mask)) 71 return -EINVAL; 72 73 if (copy_from_user(&new_mask, user_mask_ptr, sizeof(new_mask))) 74 return -EFAULT; 75 76 get_online_cpus(); 77 rcu_read_lock(); 78 79 p = find_process_by_pid(pid); 80 if (!p) { 81 rcu_read_unlock(); 82 put_online_cpus(); 83 return -ESRCH; 84 } 85 86 /* Prevent p going away */ 87 get_task_struct(p); 88 rcu_read_unlock(); 89 90 if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) { 91 retval = -ENOMEM; 92 goto out_put_task; 93 } 94 if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) { 95 retval = -ENOMEM; 96 goto out_free_cpus_allowed; 97 } 98 if (!alloc_cpumask_var(&effective_mask, GFP_KERNEL)) { 99 retval = -ENOMEM; 100 goto out_free_new_mask; 101 } 102 retval = -EPERM; 103 if (!check_same_owner(p) && !capable(CAP_SYS_NICE)) 104 goto out_unlock; 105 106 retval = security_task_setscheduler(p); 107 if (retval) 108 goto out_unlock; 109 110 /* Record new user-specified CPU set for future reference */ 111 cpumask_copy(&p->thread.user_cpus_allowed, new_mask); 112 113 again: 114 /* Compute new global allowed CPU set if necessary */ 115 ti = task_thread_info(p); 116 if (test_ti_thread_flag(ti, TIF_FPUBOUND) && 117 cpus_intersects(*new_mask, mt_fpu_cpumask)) { 118 cpus_and(*effective_mask, *new_mask, mt_fpu_cpumask); 119 retval = set_cpus_allowed_ptr(p, effective_mask); 120 } else { 121 cpumask_copy(effective_mask, new_mask); 122 clear_ti_thread_flag(ti, TIF_FPUBOUND); 123 retval = set_cpus_allowed_ptr(p, new_mask); 124 } 125 126 if (!retval) { 127 cpuset_cpus_allowed(p, cpus_allowed); 128 if (!cpumask_subset(effective_mask, cpus_allowed)) { 129 /* 130 * We must have raced with a concurrent cpuset 131 * update. Just reset the cpus_allowed to the 132 * cpuset's cpus_allowed 133 */ 134 cpumask_copy(new_mask, cpus_allowed); 135 goto again; 136 } 137 } 138 out_unlock: 139 free_cpumask_var(effective_mask); 140 out_free_new_mask: 141 free_cpumask_var(new_mask); 142 out_free_cpus_allowed: 143 free_cpumask_var(cpus_allowed); 144 out_put_task: 145 put_task_struct(p); 146 put_online_cpus(); 147 return retval; 148 } 149 150 /* 151 * mipsmt_sys_sched_getaffinity - get the cpu affinity of a process 152 */ 153 asmlinkage long mipsmt_sys_sched_getaffinity(pid_t pid, unsigned int len, 154 unsigned long __user *user_mask_ptr) 155 { 156 unsigned int real_len; 157 cpumask_t mask; 158 int retval; 159 struct task_struct *p; 160 161 real_len = sizeof(mask); 162 if (len < real_len) 163 return -EINVAL; 164 165 get_online_cpus(); 166 read_lock(&tasklist_lock); 167 168 retval = -ESRCH; 169 p = find_process_by_pid(pid); 170 if (!p) 171 goto out_unlock; 172 retval = security_task_getscheduler(p); 173 if (retval) 174 goto out_unlock; 175 176 cpumask_and(&mask, &p->thread.user_cpus_allowed, cpu_possible_mask); 177 178 out_unlock: 179 read_unlock(&tasklist_lock); 180 put_online_cpus(); 181 if (retval) 182 return retval; 183 if (copy_to_user(user_mask_ptr, &mask, real_len)) 184 return -EFAULT; 185 return real_len; 186 } 187 188 189 static int __init fpaff_thresh(char *str) 190 { 191 get_option(&str, &fpaff_threshold); 192 return 1; 193 } 194 __setup("fpaff=", fpaff_thresh); 195 196 /* 197 * FPU Use Factor empirically derived from experiments on 34K 198 */ 199 #define FPUSEFACTOR 2000 200 201 static __init int mt_fp_affinity_init(void) 202 { 203 if (fpaff_threshold >= 0) { 204 mt_fpemul_threshold = fpaff_threshold; 205 } else { 206 mt_fpemul_threshold = 207 (FPUSEFACTOR * (loops_per_jiffy/(500000/HZ))) / HZ; 208 } 209 printk(KERN_DEBUG "FPU Affinity set after %ld emulations\n", 210 mt_fpemul_threshold); 211 212 return 0; 213 } 214 arch_initcall(mt_fp_affinity_init); 215