mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-26 04:31:03 +00:00
5a82c74822
Also, change sources.redhat.com to sourceware.org.
This patch was automatically generated by running the following shell
script, which uses GNU sed, and which avoids modifying files imported
from upstream:
sed -ri '
s,(http|ftp)(://(.*\.)?(gnu|fsf|sourceware)\.org($|[^.]|\.[^a-z])),https\2,g
s,(http|ftp)(://(.*\.)?)sources\.redhat\.com($|[^.]|\.[^a-z]),https\2sourceware.org\4,g
' \
$(find $(git ls-files) -prune -type f \
! -name '*.po' \
! -name 'ChangeLog*' \
! -path COPYING ! -path COPYING.LIB \
! -path manual/fdl-1.3.texi ! -path manual/lgpl-2.1.texi \
! -path manual/texinfo.tex ! -path scripts/config.guess \
! -path scripts/config.sub ! -path scripts/install-sh \
! -path scripts/mkinstalldirs ! -path scripts/move-if-change \
! -path INSTALL ! -path locale/programs/charmap-kw.h \
! -path po/libc.pot ! -path sysdeps/gnu/errlist.c \
! '(' -name configure \
-execdir test -f configure.ac -o -f configure.in ';' ')' \
! '(' -name preconfigure \
-execdir test -f preconfigure.ac ';' ')' \
-print)
and then by running 'make dist-prepare' to regenerate files built
from the altered files, and then executing the following to cleanup:
chmod a+x sysdeps/unix/sysv/linux/riscv/configure
# Omit irrelevant whitespace and comment-only changes,
# perhaps from a slightly-different Autoconf version.
git checkout -f \
sysdeps/csky/configure \
sysdeps/hppa/configure \
sysdeps/riscv/configure \
sysdeps/unix/sysv/linux/csky/configure
# Omit changes that caused a pre-commit check to fail like this:
# remote: *** error: sysdeps/powerpc/powerpc64/ppc-mcount.S: trailing lines
git checkout -f \
sysdeps/powerpc/powerpc64/ppc-mcount.S \
sysdeps/unix/sysv/linux/s390/s390-64/syscall.S
# Omit change that caused a pre-commit check to fail like this:
# remote: *** error: sysdeps/sparc/sparc64/multiarch/memcpy-ultra3.S: last line does not end in newline
git checkout -f sysdeps/sparc/sparc64/multiarch/memcpy-ultra3.S
69 lines
3.0 KiB
C
69 lines
3.0 KiB
C
/* Copyright (C) 2002-2019 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
|
|
|
|
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 <errno.h>
|
|
#include "pthreadP.h"
|
|
#include <atomic.h>
|
|
|
|
/* See pthread_rwlock_common.c for an overview. */
|
|
int
|
|
__pthread_rwlock_trywrlock (pthread_rwlock_t *rwlock)
|
|
{
|
|
/* When in a trywrlock, we can acquire the write lock if it is in states
|
|
#1 (idle and read phase) and #5 (idle and write phase), and also in #6
|
|
(readers waiting, write phase) if we prefer writers.
|
|
If we observe any other state, we are allowed to fail and do not need to
|
|
"synchronize memory" as specified by POSIX (hence relaxed MO is
|
|
sufficient for the first load and the CAS failure path).
|
|
We face a similar issue as in tryrdlock in that we need to both avoid
|
|
live-locks / starvation and must not fail spuriously (see there for
|
|
further comments) -- and thus must loop until we get a definitive
|
|
observation or state change. */
|
|
unsigned int r = atomic_load_relaxed (&rwlock->__data.__readers);
|
|
bool prefer_writer =
|
|
(rwlock->__data.__flags != PTHREAD_RWLOCK_PREFER_READER_NP);
|
|
while (((r & PTHREAD_RWLOCK_WRLOCKED) == 0)
|
|
&& (((r >> PTHREAD_RWLOCK_READER_SHIFT) == 0)
|
|
|| (prefer_writer && ((r & PTHREAD_RWLOCK_WRPHASE) != 0))))
|
|
{
|
|
/* Try to transition to states #7 or #8 (i.e., acquire the lock). */
|
|
if (atomic_compare_exchange_weak_acquire (
|
|
&rwlock->__data.__readers, &r,
|
|
r | PTHREAD_RWLOCK_WRPHASE | PTHREAD_RWLOCK_WRLOCKED))
|
|
{
|
|
/* We have become the primary writer and we cannot have shared
|
|
the PTHREAD_RWLOCK_FUTEX_USED flag with someone else, so we
|
|
can simply enable blocking (see full wrlock code). */
|
|
atomic_store_relaxed (&rwlock->__data.__writers_futex, 1);
|
|
/* If we started a write phase, we need to enable readers to
|
|
wait. If we did not, we must not change it because other threads
|
|
may have set the PTHREAD_RWLOCK_FUTEX_USED in the meantime. */
|
|
if ((r & PTHREAD_RWLOCK_WRPHASE) == 0)
|
|
atomic_store_relaxed (&rwlock->__data.__wrphase_futex, 1);
|
|
atomic_store_relaxed (&rwlock->__data.__cur_writer,
|
|
THREAD_GETMEM (THREAD_SELF, tid));
|
|
return 0;
|
|
}
|
|
/* TODO Back-off. */
|
|
/* See above. */
|
|
}
|
|
return EBUSY;
|
|
}
|
|
|
|
strong_alias (__pthread_rwlock_trywrlock, pthread_rwlock_trywrlock)
|