nptl/tpp.c

   1 /* Thread Priority Protect helpers.
   2    Copyright (C) 2006 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, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <assert.h>
  22 #include <atomic.h>
  23 #include <errno.h>
  24 #include <pthreadP.h>
  25 #include <sched.h>
  26 #include <stdlib.h>
  27
  28
  29 int __sched_fifo_min_prio = -1;
  30 int __sched_fifo_max_prio = -1;
  31
  32 void
  33 __init_sched_fifo_prio (void)
  34 {
  35   __sched_fifo_max_prio = sched_get_priority_max (SCHED_FIFO);
  36   atomic_write_barrier ();
  37   __sched_fifo_min_prio = sched_get_priority_min (SCHED_FIFO);
  38 }
  39
  40 int
  41 __pthread_tpp_change_priority (int previous_prio, int new_prio)
  42 {
  43   struct pthread *self = THREAD_SELF;
  44   struct priority_protection_data *tpp = THREAD_GETMEM (self, tpp);
  45
  46   if (tpp == NULL)
  47     {
  48       if (__sched_fifo_min_prio == -1)
  49         __init_sched_fifo_prio ();
  50
  51       size_t size = sizeof *tpp;
  52       size += (__sched_fifo_max_prio - __sched_fifo_min_prio + 1)
  53               * sizeof (tpp->priomap[0]);
  54       tpp = calloc (size, 1);
  55       if (tpp == NULL)
  56         return ENOMEM;
  57       tpp->priomax = __sched_fifo_min_prio - 1;
  58       THREAD_SETMEM (self, tpp, tpp);
  59     }
  60
  61   assert (new_prio == -1
  62           || (new_prio >= __sched_fifo_min_prio
  63               && new_prio <= __sched_fifo_max_prio));
  64   assert (previous_prio == -1
  65           || (previous_prio >= __sched_fifo_min_prio
  66               && previous_prio <= __sched_fifo_max_prio));
  67
  68   int priomax = tpp->priomax;
  69   int newpriomax = priomax;
  70   if (new_prio != -1)
  71     {
  72       if (tpp->priomap[new_prio - __sched_fifo_min_prio] + 1 == 0)
  73         return EAGAIN;
  74       ++tpp->priomap[new_prio - __sched_fifo_min_prio];
  75       if (new_prio > priomax)
  76         newpriomax = new_prio;
  77     }
  78
  79   if (previous_prio != -1)
  80     {
  81       if (--tpp->priomap[previous_prio - __sched_fifo_min_prio] == 0
  82           && priomax == previous_prio
  83           && previous_prio > new_prio)
  84         {
  85           int i;
  86           for (i = previous_prio - 1; i >= __sched_fifo_min_prio; --i)
  87             if (tpp->priomap[i - __sched_fifo_min_prio])
  88               break;
  89           newpriomax = i;
  90         }
  91     }
  92
  93   if (priomax == newpriomax)
  94     return 0;
  95
  96   lll_lock (self->lock);
  97
  98   tpp->priomax = newpriomax;
  99
 100   int result = 0;
 101
 102   if ((self->flags & ATTR_FLAG_SCHED_SET) == 0)
 103     {
 104       if (__sched_getparam (self->tid, &self->schedparam) != 0)
 105         result = errno;
 106       else
 107         self->flags |= ATTR_FLAG_SCHED_SET;
 108     }
 109
 110   if ((self->flags & ATTR_FLAG_POLICY_SET) == 0)
 111     {
 112       self->schedpolicy = __sched_getscheduler (self->tid);
 113       if (self->schedpolicy == -1)
 114         result = errno;
 115       else
 116         self->flags |= ATTR_FLAG_POLICY_SET;
 117     }
 118
 119   if (result == 0)
 120     {
 121       struct sched_param sp = self->schedparam;
 122       if (sp.sched_priority < newpriomax || sp.sched_priority < priomax)
 123         {
 124           if (sp.sched_priority < newpriomax)
 125             sp.sched_priority = newpriomax;
 126
 127           if (__sched_setscheduler (self->tid, self->schedpolicy, &sp) < 0)
 128             result = errno;
 129         }
 130     }
 131
 132   lll_unlock (self->lock);
 133
 134   return result;
 135 }
 136
 137 int
 138 __pthread_current_priority (void)
 139 {
 140   struct pthread *self = THREAD_SELF;
 141   if ((self->flags & (ATTR_FLAG_POLICY_SET | ATTR_FLAG_SCHED_SET))
 142       == (ATTR_FLAG_POLICY_SET | ATTR_FLAG_SCHED_SET))
 143     return self->schedparam.sched_priority;
 144
 145   int result = 0;
 146
 147   lll_lock (self->lock);
 148
 149   if ((self->flags & ATTR_FLAG_SCHED_SET) == 0)
 150     {
 151       if (__sched_getparam (self->tid, &self->schedparam) != 0)
 152         result = -1;
 153       else
 154         self->flags |= ATTR_FLAG_SCHED_SET;
 155     }
 156
 157   if ((self->flags & ATTR_FLAG_POLICY_SET) == 0)
 158     {
 159       self->schedpolicy = __sched_getscheduler (self->tid);
 160       if (self->schedpolicy == -1)
 161         result = -1;
 162       else
 163         self->flags |= ATTR_FLAG_POLICY_SET;
 164     }
 165
 166   if (result != -1)
 167     result = self->schedparam.sched_priority;
 168
 169   lll_unlock (self->lock);
 170
 171   return result;
 172 }