mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-22 13:00:06 +00:00
130 lines
3.8 KiB
C
130 lines
3.8 KiB
C
/* Copyright (C) 2003-2016 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003.
|
|
|
|
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
|
|
<http://www.gnu.org/licenses/>. */
|
|
|
|
#include <errno.h>
|
|
#include <sysdep.h>
|
|
#include <lowlevellock.h>
|
|
#include <futex-internal.h>
|
|
#include <pthread.h>
|
|
#include <pthreadP.h>
|
|
#include <stap-probe.h>
|
|
#include <elide.h>
|
|
|
|
|
|
/* Acquire write lock for RWLOCK. */
|
|
static int __attribute__((noinline))
|
|
__pthread_rwlock_wrlock_slow (pthread_rwlock_t *rwlock)
|
|
{
|
|
int result = 0;
|
|
int futex_shared =
|
|
rwlock->__data.__shared == LLL_PRIVATE ? FUTEX_PRIVATE : FUTEX_SHARED;
|
|
|
|
/* Caller has taken the lock. */
|
|
|
|
while (1)
|
|
{
|
|
/* Make sure we are not holding the rwlock as a writer. This is
|
|
a deadlock situation we recognize and report. */
|
|
if (__builtin_expect (rwlock->__data.__writer
|
|
== THREAD_GETMEM (THREAD_SELF, tid), 0))
|
|
{
|
|
result = EDEADLK;
|
|
break;
|
|
}
|
|
|
|
/* Remember that we are a writer. */
|
|
if (++rwlock->__data.__nr_writers_queued == 0)
|
|
{
|
|
/* Overflow on number of queued writers. */
|
|
--rwlock->__data.__nr_writers_queued;
|
|
result = EAGAIN;
|
|
break;
|
|
}
|
|
|
|
int waitval = rwlock->__data.__writer_wakeup;
|
|
|
|
/* Free the lock. */
|
|
lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
|
|
|
|
/* Wait for the writer or reader(s) to finish. We do not check the
|
|
return value because we decide how to continue based on the state of
|
|
the rwlock. */
|
|
futex_wait_simple (&rwlock->__data.__writer_wakeup, waitval,
|
|
futex_shared);
|
|
|
|
/* Get the lock. */
|
|
lll_lock (rwlock->__data.__lock, rwlock->__data.__shared);
|
|
|
|
/* To start over again, remove the thread from the writer list. */
|
|
--rwlock->__data.__nr_writers_queued;
|
|
|
|
/* Get the rwlock if there is no writer and no reader. */
|
|
if (rwlock->__data.__writer == 0 && rwlock->__data.__nr_readers == 0)
|
|
{
|
|
/* Mark self as writer. */
|
|
rwlock->__data.__writer = THREAD_GETMEM (THREAD_SELF, tid);
|
|
|
|
LIBC_PROBE (wrlock_acquire_write, 1, rwlock);
|
|
break;
|
|
}
|
|
}
|
|
|
|
/* We are done, free the lock. */
|
|
lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
|
|
|
|
return result;
|
|
}
|
|
|
|
/* Fast path of acquiring write lock for RWLOCK. */
|
|
|
|
int
|
|
__pthread_rwlock_wrlock (pthread_rwlock_t *rwlock)
|
|
{
|
|
LIBC_PROBE (wrlock_entry, 1, rwlock);
|
|
|
|
if (ELIDE_LOCK (rwlock->__data.__rwelision,
|
|
rwlock->__data.__lock == 0
|
|
&& rwlock->__data.__writer == 0
|
|
&& rwlock->__data.__nr_readers == 0))
|
|
return 0;
|
|
|
|
/* Make sure we are alone. */
|
|
lll_lock (rwlock->__data.__lock, rwlock->__data.__shared);
|
|
|
|
/* Get the rwlock if there is no writer and no reader. */
|
|
if (__glibc_likely((rwlock->__data.__writer |
|
|
rwlock->__data.__nr_readers) == 0))
|
|
{
|
|
/* Mark self as writer. */
|
|
rwlock->__data.__writer = THREAD_GETMEM (THREAD_SELF, tid);
|
|
|
|
LIBC_PROBE (wrlock_acquire_write, 1, rwlock);
|
|
|
|
/* We are done, free the lock. */
|
|
lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
|
|
|
|
return 0;
|
|
}
|
|
|
|
return __pthread_rwlock_wrlock_slow (rwlock);
|
|
}
|
|
|
|
|
|
weak_alias (__pthread_rwlock_wrlock, pthread_rwlock_wrlock)
|
|
hidden_def (__pthread_rwlock_wrlock)
|