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/* worker_mutex.c -*-C-*-
*
*************************************************************************
*
* @copyright
* Copyright (C) 2009-2011
* Intel Corporation
*
* @copyright
* This file is part of the Intel Cilk Plus Library. This library is free
* software; you can redistribute it and/or modify it under the
* terms of the GNU General Public License as published by the
* Free Software Foundation; either version 3, or (at your option)
* any later version.
*
* @copyright
* This 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 General Public License for more details.
*
* @copyright
* Under Section 7 of GPL version 3, you are granted additional
* permissions described in the GCC Runtime Library Exception, version
* 3.1, as published by the Free Software Foundation.
*
* @copyright
* You should have received a copy of the GNU General Public License and
* a copy of the GCC Runtime Library Exception along with this program;
* see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
* <http://www.gnu.org/licenses/>.
**************************************************************************/
#include "worker_mutex.h"
#include "bug.h"
#include "os.h"
#include "stats.h"
/* m->lock == 1 means that mutex M is locked */
#define TRY_ACQUIRE(m) (__cilkrts_xchg(&(m)->lock, 1) == 0)
/* ICC 11.1+ understands release semantics and generates an
ordinary store with a software memory barrier. */
#if __ICC >= 1110
#define RELEASE(m) __sync_lock_release(&(m)->lock)
#else
#define RELEASE(m) __cilkrts_xchg(&(m)->lock, 0)
#endif
void __cilkrts_mutex_init(struct mutex *m)
{
m->owner = 0;
// Use a simple assignment so Inspector doesn't bug us about the
// interlocked exchange doing a read of an uninitialized variable.
// By definition there can't be a race when we're initializing the
// lock...
m->lock = 0;
}
void __cilkrts_mutex_lock(__cilkrts_worker *w, struct mutex *m)
{
int count;
const int maxspin = 1000; /* SWAG */
NOTE_INTERVAL(w, INTERVAL_MUTEX_LOCK);
if (!TRY_ACQUIRE(m)) {
START_INTERVAL(w, INTERVAL_MUTEX_LOCK_SPINNING);
count = 0;
do {
do {
__cilkrts_short_pause();
if (++count >= maxspin) {
STOP_INTERVAL(w, INTERVAL_MUTEX_LOCK_SPINNING);
START_INTERVAL(w, INTERVAL_MUTEX_LOCK_YIELDING);
/* let the OS reschedule every once in a while */
__cilkrts_yield();
STOP_INTERVAL(w, INTERVAL_MUTEX_LOCK_YIELDING);
START_INTERVAL(w, INTERVAL_MUTEX_LOCK_SPINNING);
count = 0;
}
} while (m->lock != 0);
} while (!TRY_ACQUIRE(m));
STOP_INTERVAL(w, INTERVAL_MUTEX_LOCK_SPINNING);
}
CILK_ASSERT(m->owner == 0);
m->owner = w;
}
int __cilkrts_mutex_trylock(__cilkrts_worker *w, struct mutex *m)
{
NOTE_INTERVAL(w, INTERVAL_MUTEX_TRYLOCK);
if (TRY_ACQUIRE(m)) {
CILK_ASSERT(m->owner == 0);
m->owner = w;
return 1;
} else {
return 0;
}
}
void __cilkrts_mutex_unlock(__cilkrts_worker *w, struct mutex *m)
{
CILK_ASSERT(m->owner == w);
m->owner = 0;
RELEASE(m);
}
void __cilkrts_mutex_destroy(__cilkrts_worker *w, struct mutex *m)
{
(void)w; /* unused */
(void)m; /* unused */
}
/* End worker_mutex.c */
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