nptl/tpp.c

   1 /* Thread Priority Protect helpers.
   2    Copyright (C) 2006-2013 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Jakub Jelinek <jakub@redhat.com>, 2006.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <assert.h>
  21 #include <atomic.h>
  22 #include <errno.h>
  23 #include <pthreadP.h>
  24 #include <sched.h>
  25 #include <stdlib.h>
  26
  27
  28 int __sched_fifo_min_prio = -1;
  29 int __sched_fifo_max_prio = -1;
  30
  31 void
  32 __init_sched_fifo_prio (void)
  33 {
  34   __sched_fifo_max_prio = sched_get_priority_max (SCHED_FIFO);
  35   atomic_write_barrier ();
  36   __sched_fifo_min_prio = sched_get_priority_min (SCHED_FIFO);
  37 }
  38
  39 int
  40 __pthread_tpp_change_priority (int previous_prio, int new_prio)
  41 {
  42   struct pthread *self = THREAD_SELF;
  43   struct priority_protection_data *tpp = THREAD_GETMEM (self, tpp);
  44
  45   if (tpp == NULL)
  46     {
  47       if (__sched_fifo_min_prio == -1)
  48         __init_sched_fifo_prio ();
  49
  50       size_t size = sizeof *tpp;
  51       size += (__sched_fifo_max_prio - __sched_fifo_min_prio + 1)
  52               * sizeof (tpp->priomap[0]);
  53       tpp = calloc (size, 1);
  54       if (tpp == NULL)
  55         return ENOMEM;
  56       tpp->priomax = __sched_fifo_min_prio - 1;
  57       THREAD_SETMEM (self, tpp, tpp);
  58     }
  59
  60   assert (new_prio == -1
  61           || (new_prio >= __sched_fifo_min_prio
  62               && new_prio <= __sched_fifo_max_prio));
  63   assert (previous_prio == -1
  64           || (previous_prio >= __sched_fifo_min_prio
  65               && previous_prio <= __sched_fifo_max_prio));
  66
  67   int priomax = tpp->priomax;
  68   int newpriomax = priomax;
  69   if (new_prio != -1)
  70     {
  71       if (tpp->priomap[new_prio - __sched_fifo_min_prio] + 1 == 0)
  72         return EAGAIN;
  73       ++tpp->priomap[new_prio - __sched_fifo_min_prio];
  74       if (new_prio > priomax)
  75         newpriomax = new_prio;
  76     }
  77
  78   if (previous_prio != -1)
  79     {
  80       if (--tpp->priomap[previous_prio - __sched_fifo_min_prio] == 0
  81           && priomax == previous_prio
  82           && previous_prio > new_prio)
  83         {
  84           int i;
  85           for (i = previous_prio - 1; i >= __sched_fifo_min_prio; --i)
  86             if (tpp->priomap[i - __sched_fifo_min_prio])
  87               break;
  88           newpriomax = i;
  89         }
  90     }
  91
  92   if (priomax == newpriomax)
  93     return 0;
  94
  95   lll_lock (self->lock, LLL_PRIVATE);
  96
  97   tpp->priomax = newpriomax;
  98
  99   int result = 0;
 100
 101   if ((self->flags & ATTR_FLAG_SCHED_SET) == 0)
 102     {
 103       if (__sched_getparam (self->tid, &self->schedparam) != 0)
 104         result = errno;
 105       else
 106         self->flags |= ATTR_FLAG_SCHED_SET;
 107     }
 108
 109   if ((self->flags & ATTR_FLAG_POLICY_SET) == 0)
 110     {
 111       self->schedpolicy = __sched_getscheduler (self->tid);
 112       if (self->schedpolicy == -1)
 113         result = errno;
 114       else
 115         self->flags |= ATTR_FLAG_POLICY_SET;
 116     }
 117
 118   if (result == 0)
 119     {
 120       struct sched_param sp = self->schedparam;
 121       if (sp.sched_priority < newpriomax || sp.sched_priority < priomax)
 122         {
 123           if (sp.sched_priority < newpriomax)
 124             sp.sched_priority = newpriomax;
 125
 126           if (__sched_setscheduler (self->tid, self->schedpolicy, &sp) < 0)
 127             result = errno;
 128         }
 129     }
 130
 131   lll_unlock (self->lock, LLL_PRIVATE);
 132
 133   return result;
 134 }
 135
 136 int
 137 __pthread_current_priority (void)
 138 {
 139   struct pthread *self = THREAD_SELF;
 140   if ((self->flags & (ATTR_FLAG_POLICY_SET | ATTR_FLAG_SCHED_SET))
 141       == (ATTR_FLAG_POLICY_SET | ATTR_FLAG_SCHED_SET))
 142     return self->schedparam.sched_priority;
 143
 144   int result = 0;
 145
 146   lll_lock (self->lock, LLL_PRIVATE);
 147
 148   if ((self->flags & ATTR_FLAG_SCHED_SET) == 0)
 149     {
 150       if (__sched_getparam (self->tid, &self->schedparam) != 0)
 151         result = -1;
 152       else
 153         self->flags |= ATTR_FLAG_SCHED_SET;
 154     }
 155
 156   if ((self->flags & ATTR_FLAG_POLICY_SET) == 0)
 157     {
 158       self->schedpolicy = __sched_getscheduler (self->tid);
 159       if (self->schedpolicy == -1)
 160         result = -1;
 161       else
 162         self->flags |= ATTR_FLAG_POLICY_SET;
 163     }
 164
 165   if (result != -1)
 166     result = self->schedparam.sched_priority;
 167
 168   lll_unlock (self->lock, LLL_PRIVATE);
 169
 170   return result;
 171 }