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