arch/mips/kernel/mips-mt-fpaff.c

   1 /*
   2  * General MIPS MT support routines, usable in AP/SP and SMVP.
   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/sched/task.h>
  13 #include <linux/cred.h>
  14 #include <linux/security.h>
  15 #include <linux/types.h>
  16 #include <linux/uaccess.h>
  17
  18 /*
  19  * CPU mask used to set process affinity for MT VPEs/TCs with FPUs
  20  */
  21 cpumask_t mt_fpu_cpumask;
  22
  23 static int fpaff_threshold = -1;
  24 unsigned long mt_fpemul_threshold;
  25
  26 /*
  27  * Replacement functions for the sys_sched_setaffinity() and
  28  * sys_sched_getaffinity() system calls, so that we can integrate
  29  * FPU affinity with the user's requested processor affinity.
  30  * This code is 98% identical with the sys_sched_setaffinity()
  31  * and sys_sched_getaffinity() system calls, and should be
  32  * updated when kernel/sched/core.c changes.
  33  */
  34
  35 /*
  36  * find_process_by_pid - find a process with a matching PID value.
  37  * used in sys_sched_set/getaffinity() in kernel/sched/core.c, so
  38  * cloned here.
  39  */
  40 static inline struct task_struct *find_process_by_pid(pid_t pid)
  41 {
  42         return pid ? find_task_by_vpid(pid) : current;
  43 }
  44
  45 /*
  46  * check the target process has a UID that matches the current process's
  47  */
  48 static bool check_same_owner(struct task_struct *p)
  49 {
  50         const struct cred *cred = current_cred(), *pcred;
  51         bool match;
  52
  53         rcu_read_lock();
  54         pcred = __task_cred(p);
  55         match = (uid_eq(cred->euid, pcred->euid) ||
  56                  uid_eq(cred->euid, pcred->uid));
  57         rcu_read_unlock();
  58         return match;
  59 }
  60
  61 /*
  62  * mipsmt_sys_sched_setaffinity - set the cpu affinity of a process
  63  */
  64 asmlinkage long mipsmt_sys_sched_setaffinity(pid_t pid, unsigned int len,
  65                                       unsigned long __user *user_mask_ptr)
  66 {
  67         cpumask_var_t cpus_allowed, new_mask, effective_mask;
  68         struct thread_info *ti;
  69         struct task_struct *p;
  70         int retval;
  71
  72         if (len < sizeof(new_mask))
  73                 return -EINVAL;
  74
  75         if (copy_from_user(&new_mask, user_mask_ptr, sizeof(new_mask)))
  76                 return -EFAULT;
  77
  78         get_online_cpus();
  79         rcu_read_lock();
  80
  81         p = find_process_by_pid(pid);
  82         if (!p) {
  83                 rcu_read_unlock();
  84                 put_online_cpus();
  85                 return -ESRCH;
  86         }
  87
  88         /* Prevent p going away */
  89         get_task_struct(p);
  90         rcu_read_unlock();
  91
  92         if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
  93                 retval = -ENOMEM;
  94                 goto out_put_task;
  95         }
  96         if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
  97                 retval = -ENOMEM;
  98                 goto out_free_cpus_allowed;
  99         }
 100         if (!alloc_cpumask_var(&effective_mask, GFP_KERNEL)) {
 101                 retval = -ENOMEM;
 102                 goto out_free_new_mask;
 103         }
 104         if (!check_same_owner(p) && !capable(CAP_SYS_NICE)) {
 105                 retval = -EPERM;
 106                 goto out_unlock;
 107         }
 108
 109         retval = security_task_setscheduler(p);
 110         if (retval)
 111                 goto out_unlock;
 112
 113         /* Record new user-specified CPU set for future reference */
 114         cpumask_copy(&p->thread.user_cpus_allowed, new_mask);
 115
 116  again:
 117         /* Compute new global allowed CPU set if necessary */
 118         ti = task_thread_info(p);
 119         if (test_ti_thread_flag(ti, TIF_FPUBOUND) &&
 120             cpumask_intersects(new_mask, &mt_fpu_cpumask)) {
 121                 cpumask_and(effective_mask, new_mask, &mt_fpu_cpumask);
 122                 retval = set_cpus_allowed_ptr(p, effective_mask);
 123         } else {
 124                 cpumask_copy(effective_mask, new_mask);
 125                 clear_ti_thread_flag(ti, TIF_FPUBOUND);
 126                 retval = set_cpus_allowed_ptr(p, new_mask);
 127         }
 128
 129         if (!retval) {
 130                 cpuset_cpus_allowed(p, cpus_allowed);
 131                 if (!cpumask_subset(effective_mask, cpus_allowed)) {
 132                         /*
 133                          * We must have raced with a concurrent cpuset
 134                          * update. Just reset the cpus_allowed to the
 135                          * cpuset's cpus_allowed
 136                          */
 137                         cpumask_copy(new_mask, cpus_allowed);
 138                         goto again;
 139                 }
 140         }
 141 out_unlock:
 142         free_cpumask_var(effective_mask);
 143 out_free_new_mask:
 144         free_cpumask_var(new_mask);
 145 out_free_cpus_allowed:
 146         free_cpumask_var(cpus_allowed);
 147 out_put_task:
 148         put_task_struct(p);
 149         put_online_cpus();
 150         return retval;
 151 }
 152
 153 /*
 154  * mipsmt_sys_sched_getaffinity - get the cpu affinity of a process
 155  */
 156 asmlinkage long mipsmt_sys_sched_getaffinity(pid_t pid, unsigned int len,
 157                                       unsigned long __user *user_mask_ptr)
 158 {
 159         unsigned int real_len;
 160         cpumask_t allowed, mask;
 161         int retval;
 162         struct task_struct *p;
 163
 164         real_len = sizeof(mask);
 165         if (len < real_len)
 166                 return -EINVAL;
 167
 168         get_online_cpus();
 169         read_lock(&tasklist_lock);
 170
 171         retval = -ESRCH;
 172         p = find_process_by_pid(pid);
 173         if (!p)
 174                 goto out_unlock;
 175         retval = security_task_getscheduler(p);
 176         if (retval)
 177                 goto out_unlock;
 178
 179         cpumask_or(&allowed, &p->thread.user_cpus_allowed, &p->cpus_allowed);
 180         cpumask_and(&mask, &allowed, cpu_active_mask);
 181
 182 out_unlock:
 183         read_unlock(&tasklist_lock);
 184         put_online_cpus();
 185         if (retval)
 186                 return retval;
 187         if (copy_to_user(user_mask_ptr, &mask, real_len))
 188                 return -EFAULT;
 189         return real_len;
 190 }
 191
 192
 193 static int __init fpaff_thresh(char *str)
 194 {
 195         get_option(&str, &fpaff_threshold);
 196         return 1;
 197 }
 198 __setup("fpaff=", fpaff_thresh);
 199
 200 /*
 201  * FPU Use Factor empirically derived from experiments on 34K
 202  */
 203 #define FPUSEFACTOR 2000
 204
 205 static __init int mt_fp_affinity_init(void)
 206 {
 207         if (fpaff_threshold >= 0) {
 208                 mt_fpemul_threshold = fpaff_threshold;
 209         } else {
 210                 mt_fpemul_threshold =
 211                         (FPUSEFACTOR * (loops_per_jiffy/(500000/HZ))) / HZ;
 212         }
 213         printk(KERN_DEBUG "FPU Affinity set after %ld emulations\n",
 214                mt_fpemul_threshold);
 215
 216         return 0;
 217 }
 218 arch_initcall(mt_fp_affinity_init);