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

   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/cpumask.h>
   7 #include <linux/delay.h>
   8 #include <linux/kernel.h>
   9 #include <linux/init.h>
  10 #include <linux/sched.h>
  11 #include <linux/security.h>
  12 #include <linux/types.h>
  13 #include <asm/uaccess.h>
  14
  15 /*
  16  * CPU mask used to set process affinity for MT VPEs/TCs with FPUs
  17  */
  18 cpumask_t mt_fpu_cpumask;
  19
  20 static int fpaff_threshold = -1;
  21 unsigned long mt_fpemul_threshold = 0;
  22
  23 /*
  24  * Replacement functions for the sys_sched_setaffinity() and
  25  * sys_sched_getaffinity() system calls, so that we can integrate
  26  * FPU affinity with the user's requested processor affinity.
  27  * This code is 98% identical with the sys_sched_setaffinity()
  28  * and sys_sched_getaffinity() system calls, and should be
  29  * updated when kernel/sched.c changes.
  30  */
  31
  32 /*
  33  * find_process_by_pid - find a process with a matching PID value.
  34  * used in sys_sched_set/getaffinity() in kernel/sched.c, so
  35  * cloned here.
  36  */
  37 static inline struct task_struct *find_process_by_pid(pid_t pid)
  38 {
  39         return pid ? find_task_by_pid(pid) : current;
  40 }
  41
  42
  43 /*
  44  * mipsmt_sys_sched_setaffinity - set the cpu affinity of a process
  45  */
  46 asmlinkage long mipsmt_sys_sched_setaffinity(pid_t pid, unsigned int len,
  47                                       unsigned long __user *user_mask_ptr)
  48 {
  49         cpumask_t new_mask;
  50         cpumask_t effective_mask;
  51         int retval;
  52         struct task_struct *p;
  53         struct thread_info *ti;
  54
  55         if (len < sizeof(new_mask))
  56                 return -EINVAL;
  57
  58         if (copy_from_user(&new_mask, user_mask_ptr, sizeof(new_mask)))
  59                 return -EFAULT;
  60
  61         get_online_cpus();
  62         read_lock(&tasklist_lock);
  63
  64         p = find_process_by_pid(pid);
  65         if (!p) {
  66                 read_unlock(&tasklist_lock);
  67                 put_online_cpus();
  68                 return -ESRCH;
  69         }
  70
  71         /*
  72          * It is not safe to call set_cpus_allowed with the
  73          * tasklist_lock held.  We will bump the task_struct's
  74          * usage count and drop tasklist_lock before invoking
  75          * set_cpus_allowed.
  76          */
  77         get_task_struct(p);
  78
  79         retval = -EPERM;
  80         if ((current->euid != p->euid) && (current->euid != p->uid) &&
  81                         !capable(CAP_SYS_NICE)) {
  82                 read_unlock(&tasklist_lock);
  83                 goto out_unlock;
  84         }
  85
  86         retval = security_task_setscheduler(p, 0, NULL);
  87         if (retval)
  88                 goto out_unlock;
  89
  90         /* Record new user-specified CPU set for future reference */
  91         p->thread.user_cpus_allowed = new_mask;
  92
  93         /* Unlock the task list */
  94         read_unlock(&tasklist_lock);
  95
  96         /* Compute new global allowed CPU set if necessary */
  97         ti = task_thread_info(p);
  98         if (test_ti_thread_flag(ti, TIF_FPUBOUND) &&
  99             cpus_intersects(new_mask, mt_fpu_cpumask)) {
 100                 cpus_and(effective_mask, new_mask, mt_fpu_cpumask);
 101                 retval = set_cpus_allowed(p, effective_mask);
 102         } else {
 103                 clear_ti_thread_flag(ti, TIF_FPUBOUND);
 104                 retval = set_cpus_allowed(p, new_mask);
 105         }
 106
 107 out_unlock:
 108         put_task_struct(p);
 109         put_online_cpus();
 110         return retval;
 111 }
 112
 113 /*
 114  * mipsmt_sys_sched_getaffinity - get the cpu affinity of a process
 115  */
 116 asmlinkage long mipsmt_sys_sched_getaffinity(pid_t pid, unsigned int len,
 117                                       unsigned long __user *user_mask_ptr)
 118 {
 119         unsigned int real_len;
 120         cpumask_t mask;
 121         int retval;
 122         struct task_struct *p;
 123
 124         real_len = sizeof(mask);
 125         if (len < real_len)
 126                 return -EINVAL;
 127
 128         get_online_cpus();
 129         read_lock(&tasklist_lock);
 130
 131         retval = -ESRCH;
 132         p = find_process_by_pid(pid);
 133         if (!p)
 134                 goto out_unlock;
 135         retval = security_task_getscheduler(p);
 136         if (retval)
 137                 goto out_unlock;
 138
 139         cpus_and(mask, p->thread.user_cpus_allowed, cpu_possible_map);
 140
 141 out_unlock:
 142         read_unlock(&tasklist_lock);
 143         put_online_cpus();
 144         if (retval)
 145                 return retval;
 146         if (copy_to_user(user_mask_ptr, &mask, real_len))
 147                 return -EFAULT;
 148         return real_len;
 149 }
 150
 151
 152 static int __init fpaff_thresh(char *str)
 153 {
 154         get_option(&str, &fpaff_threshold);
 155         return 1;
 156 }
 157 __setup("fpaff=", fpaff_thresh);
 158
 159 /*
 160  * FPU Use Factor empirically derived from experiments on 34K
 161  */
 162 #define FPUSEFACTOR 333
 163
 164 static __init int mt_fp_affinity_init(void)
 165 {
 166         if (fpaff_threshold >= 0) {
 167                 mt_fpemul_threshold = fpaff_threshold;
 168         } else {
 169                 mt_fpemul_threshold =
 170                         (FPUSEFACTOR * (loops_per_jiffy/(500000/HZ))) / HZ;
 171         }
 172         printk(KERN_DEBUG "FPU Affinity set after %ld emulations\n",
 173                mt_fpemul_threshold);
 174
 175         return 0;
 176 }
 177 arch_initcall(mt_fp_affinity_init);