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tile: use atomic op to unlock pthread_spinlock_t 

Atomic ops are issued directly from the core, rather than
potentially sitting in the write buffer, so can improve the
performance of other waiters.  In addition, if we didn't end
up pulling a copy of the cache line where the lock is into cache,
by using an atomic op we don't have to acquire the cache line
before we can unlock.
This commit is contained in:
Chris Metcalf 2012-11-06 09:43:58 -05:00
parent a0bce338e8
commit 351dc60c55
2 changed files with 37 additions and 0 deletions
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4
ports/ChangeLog.tile
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2012-11-06 Chris Metcalf <cmetcalf@tilera.com>
* sysdeps/tile/nptl/pthread_spin_unlock.c: New file.
2012-11-05 Chris Metcalf <cmetcalf@tilera.com>
* sysdeps/tile/math_private.h: Provide additional no-op defines

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ports/sysdeps/tile/nptl/pthread_spin_unlock.c Normal file
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/* pthread_spin_unlock -- unlock a spin lock. Tile version.
Copyright (C) 2012 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
<http://www.gnu.org/licenses/>. */
#include "pthreadP.h"
#include <atomic.h>
int
pthread_spin_unlock (pthread_spinlock_t *lock)
{
#ifdef __tilegx__
/* Use exchange() to bypass the write buffer. */
atomic_exchange_rel (lock, 0);
#else
atomic_full_barrier ();
*lock = 0;
#endif
return 0;
}