110 lines
3.5 KiB
C
110 lines
3.5 KiB
C
/* spin_mutex.c -*-C-*-
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*
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*************************************************************************
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*
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* @copyright
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* Copyright (C) 2009-2013, Intel Corporation
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* All rights reserved.
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*
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* @copyright
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* * Neither the name of Intel Corporation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* @copyright
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
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* WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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**************************************************************************/
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#include "spin_mutex.h"
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#include "bug.h"
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#include "os.h"
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#include "stats.h"
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// TBD (11/30/12): We should be doing a conditional test-xchg instead
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// of an unconditional xchg operation for the spin mutex.
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/* m->lock == 1 means that mutex M is locked */
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#define TRY_ACQUIRE(m) (__cilkrts_xchg(&(m)->lock, 1) == 0)
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/* ICC 11.1+ understands release semantics and generates an
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ordinary store with a software memory barrier. */
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#if __ICC >= 1110
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#define RELEASE(m) __sync_lock_release(&(m)->lock)
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#else
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#define RELEASE(m) __cilkrts_xchg(&(m)->lock, 0)
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#endif
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spin_mutex* spin_mutex_create()
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{
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spin_mutex* mutex = (spin_mutex*)__cilkrts_malloc(sizeof(spin_mutex));
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spin_mutex_init(mutex);
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return mutex;
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}
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void spin_mutex_init(struct spin_mutex *m)
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{
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// Use a simple assignment so Inspector doesn't bug us about the
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// interlocked exchange doing a read of an uninitialized variable.
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// By definition there can't be a race when we're initializing the
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// lock...
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m->lock = 0;
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}
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void spin_mutex_lock(struct spin_mutex *m)
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{
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int count;
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const int maxspin = 1000; /* SWAG */
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if (!TRY_ACQUIRE(m)) {
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count = 0;
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do {
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do {
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__cilkrts_short_pause();
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if (++count >= maxspin) {
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/* let the OS reschedule every once in a while */
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__cilkrts_yield();
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count = 0;
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}
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} while (m->lock != 0);
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} while (!TRY_ACQUIRE(m));
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}
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}
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int spin_mutex_trylock(struct spin_mutex *m)
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{
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return TRY_ACQUIRE(m);
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}
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void spin_mutex_unlock(struct spin_mutex *m)
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{
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RELEASE(m);
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}
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void spin_mutex_destroy(struct spin_mutex *m)
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{
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__cilkrts_free(m);
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}
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/* End spin_mutex.c */
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