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/* Thread Priority Protect helpers.
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Copyright (C) 2006-2018 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Jakub Jelinek <jakub@redhat.com>, 2006.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <assert.h>
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#include <atomic.h>
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#include <errno.h>
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#include <pthreadP.h>
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#include <sched.h>
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#include <stdlib.h>
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#include <atomic.h>
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int __sched_fifo_min_prio = -1;
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int __sched_fifo_max_prio = -1;
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/* We only want to initialize __sched_fifo_min_prio and __sched_fifo_max_prio
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once. The standard solution would be similar to pthread_once, but then
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readers would need to use an acquire fence. In this specific case,
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initialization is comprised of just idempotent writes to two variables
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that have an initial value of -1. Therefore, we can treat each variable as
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a separate, at-least-once initialized value. This enables using just
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relaxed MO loads and stores, but requires that consumers check for
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initialization of each value that is to be used; see
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__pthread_tpp_change_priority for an example.
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*/
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void
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__init_sched_fifo_prio (void)
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{
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atomic_store_relaxed (&__sched_fifo_max_prio,
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__sched_get_priority_max (SCHED_FIFO));
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atomic_store_relaxed (&__sched_fifo_min_prio,
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__sched_get_priority_min (SCHED_FIFO));
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}
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int
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__pthread_tpp_change_priority (int previous_prio, int new_prio)
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{
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struct pthread *self = THREAD_SELF;
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struct priority_protection_data *tpp = THREAD_GETMEM (self, tpp);
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int fifo_min_prio = atomic_load_relaxed (&__sched_fifo_min_prio);
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int fifo_max_prio = atomic_load_relaxed (&__sched_fifo_max_prio);
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if (tpp == NULL)
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{
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/* See __init_sched_fifo_prio. We need both the min and max prio,
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so need to check both, and run initialization if either one is
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not initialized. The memory model's write-read coherence rule
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makes this work. */
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if (fifo_min_prio == -1 || fifo_max_prio == -1)
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{
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__init_sched_fifo_prio ();
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fifo_min_prio = atomic_load_relaxed (&__sched_fifo_min_prio);
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fifo_max_prio = atomic_load_relaxed (&__sched_fifo_max_prio);
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}
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size_t size = sizeof *tpp;
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size += (fifo_max_prio - fifo_min_prio + 1)
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* sizeof (tpp->priomap[0]);
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tpp = calloc (size, 1);
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if (tpp == NULL)
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return ENOMEM;
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tpp->priomax = fifo_min_prio - 1;
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THREAD_SETMEM (self, tpp, tpp);
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}
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assert (new_prio == -1
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|| (new_prio >= fifo_min_prio
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&& new_prio <= fifo_max_prio));
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assert (previous_prio == -1
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|| (previous_prio >= fifo_min_prio
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&& previous_prio <= fifo_max_prio));
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int priomax = tpp->priomax;
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int newpriomax = priomax;
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if (new_prio != -1)
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{
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if (tpp->priomap[new_prio - fifo_min_prio] + 1 == 0)
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return EAGAIN;
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++tpp->priomap[new_prio - fifo_min_prio];
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if (new_prio > priomax)
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newpriomax = new_prio;
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}
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if (previous_prio != -1)
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{
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if (--tpp->priomap[previous_prio - fifo_min_prio] == 0
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&& priomax == previous_prio
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&& previous_prio > new_prio)
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{
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int i;
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for (i = previous_prio - 1; i >= fifo_min_prio; --i)
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if (tpp->priomap[i - fifo_min_prio])
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break;
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newpriomax = i;
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}
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}
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if (priomax == newpriomax)
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return 0;
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/* See CREATE THREAD NOTES in nptl/pthread_create.c. */
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lll_lock (self->lock, LLL_PRIVATE);
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tpp->priomax = newpriomax;
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int result = 0;
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if ((self->flags & ATTR_FLAG_SCHED_SET) == 0)
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{
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if (__sched_getparam (self->tid, &self->schedparam) != 0)
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result = errno;
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else
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self->flags |= ATTR_FLAG_SCHED_SET;
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}
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if ((self->flags & ATTR_FLAG_POLICY_SET) == 0)
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{
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self->schedpolicy = __sched_getscheduler (self->tid);
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if (self->schedpolicy == -1)
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result = errno;
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else
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self->flags |= ATTR_FLAG_POLICY_SET;
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}
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if (result == 0)
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{
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struct sched_param sp = self->schedparam;
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if (sp.sched_priority < newpriomax || sp.sched_priority < priomax)
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{
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if (sp.sched_priority < newpriomax)
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sp.sched_priority = newpriomax;
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if (__sched_setscheduler (self->tid, self->schedpolicy, &sp) < 0)
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result = errno;
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}
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}
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lll_unlock (self->lock, LLL_PRIVATE);
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return result;
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}
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int
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__pthread_current_priority (void)
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{
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struct pthread *self = THREAD_SELF;
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if ((self->flags & (ATTR_FLAG_POLICY_SET | ATTR_FLAG_SCHED_SET))
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== (ATTR_FLAG_POLICY_SET | ATTR_FLAG_SCHED_SET))
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return self->schedparam.sched_priority;
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int result = 0;
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/* See CREATE THREAD NOTES in nptl/pthread_create.c. */
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lll_lock (self->lock, LLL_PRIVATE);
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if ((self->flags & ATTR_FLAG_SCHED_SET) == 0)
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{
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if (__sched_getparam (self->tid, &self->schedparam) != 0)
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result = -1;
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else
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self->flags |= ATTR_FLAG_SCHED_SET;
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}
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if ((self->flags & ATTR_FLAG_POLICY_SET) == 0)
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{
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self->schedpolicy = __sched_getscheduler (self->tid);
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if (self->schedpolicy == -1)
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result = -1;
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else
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self->flags |= ATTR_FLAG_POLICY_SET;
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}
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if (result != -1)
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result = self->schedparam.sched_priority;
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lll_unlock (self->lock, LLL_PRIVATE);
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return result;
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}
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