mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-03 02:11:08 +00:00
2b778ceb40
I used these shell commands: ../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright (cd ../glibc && git commit -am"[this commit message]") and then ignored the output, which consisted lines saying "FOO: warning: copyright statement not found" for each of 6694 files FOO. I then removed trailing white space from benchtests/bench-pthread-locks.c and iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c, to work around this diagnostic from Savannah: remote: *** pre-commit check failed ... remote: *** error: lines with trailing whitespace found remote: error: hook declined to update refs/heads/master
45 lines
1.8 KiB
C
45 lines
1.8 KiB
C
/* Copyright (C) 2005-2021 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 "pthreadP.h"
|
|
|
|
int
|
|
pthread_spin_unlock (pthread_spinlock_t *lock)
|
|
{
|
|
/* CONCURRENCTY NOTES:
|
|
|
|
The atomic_exchange_rel synchronizes-with the atomic_exhange_acq in
|
|
pthread_spin_lock.
|
|
|
|
On hppa we must not use a plain `stw` to reset the guard lock. This
|
|
has to do with the kernel compare-and-swap helper that is used to
|
|
implement all of the atomic operations.
|
|
|
|
The kernel CAS helper uses its own internal locks and that means that
|
|
to create a true happens-before relationship between any two threads,
|
|
the second thread must observe the internal lock having a value of 0
|
|
(it must attempt to take the lock with ldcw). This creates the
|
|
ordering required for a second thread to observe the effects of the
|
|
RMW of the kernel CAS helper in any other thread.
|
|
|
|
Therefore if a variable is used in an atomic macro it must always be
|
|
manipulated with atomic macros in order for memory ordering rules to
|
|
be preserved. */
|
|
atomic_exchange_rel (lock, 0);
|
|
return 0;
|
|
}
|