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/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             cpumask_intersects(new_mask, &mt_fpu_cpumask)) {
 118                 cpumask_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 allowed, 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_or(&allowed, &p->thread.user_cpus_allowed, &p->cpus_allowed);
 177         cpumask_and(&mask, &allowed, cpu_active_mask);
 178
 179 out_unlock:
 180         read_unlock(&tasklist_lock);
 181         put_online_cpus();
 182         if (retval)
 183                 return retval;
 184         if (copy_to_user(user_mask_ptr, &mask, real_len))
 185                 return -EFAULT;
 186         return real_len;
 187 }
 188
 189
 190 static int __init fpaff_thresh(char *str)
 191 {
 192         get_option(&str, &fpaff_threshold);
 193         return 1;
 194 }
 195 __setup("fpaff=", fpaff_thresh);
 196
 197 /*
 198  * FPU Use Factor empirically derived from experiments on 34K
 199  */
 200 #define FPUSEFACTOR 2000
 201
 202 static __init int mt_fp_affinity_init(void)
 203 {
 204         if (fpaff_threshold >= 0) {
 205                 mt_fpemul_threshold = fpaff_threshold;
 206         } else {
 207                 mt_fpemul_threshold =
 208                         (FPUSEFACTOR * (loops_per_jiffy/(500000/HZ))) / HZ;
 209         }
 210         printk(KERN_DEBUG "FPU Affinity set after %ld emulations\n",
 211                mt_fpemul_threshold);
 212
 213         return 0;
 214 }
 215 arch_initcall(mt_fp_affinity_init);