mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-14 01:00:07 +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.
99 lines
2.5 KiB
C
99 lines
2.5 KiB
C
/* Unlock a rwlock. Generic version.
|
|
Copyright (C) 2000-2020 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 <pthread.h>
|
|
|
|
#include <pt-internal.h>
|
|
|
|
/* Unlock *RWLOCK, rescheduling a waiting writer thread or, if there
|
|
are no threads waiting for a write lock, rescheduling the reader
|
|
threads. */
|
|
int
|
|
__pthread_rwlock_unlock (pthread_rwlock_t *rwlock)
|
|
{
|
|
struct __pthread *wakeup;
|
|
|
|
__pthread_spin_wait (&rwlock->__lock);
|
|
|
|
assert (__pthread_spin_trylock (&rwlock->__held) == EBUSY);
|
|
|
|
if (rwlock->__readers > 1)
|
|
/* There are other readers. */
|
|
{
|
|
rwlock->__readers--;
|
|
__pthread_spin_unlock (&rwlock->__lock);
|
|
return 0;
|
|
}
|
|
|
|
if (rwlock->__readers == 1)
|
|
/* Last reader. */
|
|
rwlock->__readers = 0;
|
|
|
|
|
|
/* Wake someone else up. Try the writer queue first, then the
|
|
reader queue if that is empty. */
|
|
|
|
if (rwlock->__writerqueue)
|
|
{
|
|
wakeup = rwlock->__writerqueue;
|
|
__pthread_dequeue (wakeup);
|
|
|
|
/* We do not unlock RWLOCK->held: we are transferring the ownership
|
|
to the thread that we are waking up. */
|
|
|
|
__pthread_spin_unlock (&rwlock->__lock);
|
|
__pthread_wakeup (wakeup);
|
|
|
|
return 0;
|
|
}
|
|
|
|
if (rwlock->__readerqueue)
|
|
{
|
|
unsigned n = 0;
|
|
|
|
__pthread_queue_iterate (rwlock->__readerqueue, wakeup)
|
|
n++;
|
|
|
|
{
|
|
struct __pthread *wakeups[n];
|
|
unsigned i = 0;
|
|
|
|
__pthread_dequeuing_iterate (rwlock->__readerqueue, wakeup)
|
|
wakeups[i++] = wakeup;
|
|
|
|
rwlock->__readers += n;
|
|
rwlock->__readerqueue = 0;
|
|
|
|
__pthread_spin_unlock (&rwlock->__lock);
|
|
|
|
for (i = 0; i < n; i++)
|
|
__pthread_wakeup (wakeups[i]);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
|
|
/* Noone is waiting. Just unlock it. */
|
|
|
|
__pthread_spin_unlock (&rwlock->__held);
|
|
__pthread_spin_unlock (&rwlock->__lock);
|
|
return 0;
|
|
}
|
|
weak_alias (__pthread_rwlock_unlock, pthread_rwlock_unlock);
|