mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-26 15:00:06 +00:00
8ba6ad703c
900778283a ("htl: make pthread_spin_lock really spin") made
pthread_spin_lock really spin and not block, but the current users of
__pthread_spin_lock were assuming that it blocks, i.e. they use it as a
lightweight mutex fitting in just one int.
__pthread_spin_wait provides that support back.
69 lines
1.7 KiB
C
69 lines
1.7 KiB
C
/* Post a semaphore. Generic version.
|
|
Copyright (C) 2005-2020 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
|
|
The GNU C Library is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU Lesser General Public
|
|
License as published by the Free Software Foundation; either
|
|
version 2.1 of the License, or (at your option) any later version.
|
|
|
|
The GNU C Library is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
Lesser General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Lesser General Public
|
|
License along with the GNU C Library; if not, see
|
|
<https://www.gnu.org/licenses/>. */
|
|
|
|
#include <semaphore.h>
|
|
#include <assert.h>
|
|
|
|
#include <pt-internal.h>
|
|
|
|
int
|
|
__sem_post (sem_t *sem)
|
|
{
|
|
struct __pthread *wakeup;
|
|
|
|
__pthread_spin_wait (&sem->__lock);
|
|
if (sem->__value > 0)
|
|
/* Do a quick up. */
|
|
{
|
|
if (sem->__value == SEM_VALUE_MAX)
|
|
{
|
|
__pthread_spin_unlock (&sem->__lock);
|
|
errno = EOVERFLOW;
|
|
return -1;
|
|
}
|
|
|
|
assert (sem->__queue == NULL);
|
|
sem->__value++;
|
|
__pthread_spin_unlock (&sem->__lock);
|
|
return 0;
|
|
}
|
|
|
|
if (sem->__queue == NULL)
|
|
/* No one waiting. */
|
|
{
|
|
sem->__value = 1;
|
|
__pthread_spin_unlock (&sem->__lock);
|
|
return 0;
|
|
}
|
|
|
|
/* Wake someone up. */
|
|
|
|
/* First dequeue someone. */
|
|
wakeup = sem->__queue;
|
|
__pthread_dequeue (wakeup);
|
|
|
|
/* Then drop the lock and transfer control. */
|
|
__pthread_spin_unlock (&sem->__lock);
|
|
|
|
__pthread_wakeup (wakeup);
|
|
|
|
return 0;
|
|
}
|
|
|
|
strong_alias (__sem_post, sem_post);
|