libcilkrts/runtime/worker_mutex.c

   1 /* worker_mutex.c                  -*-C-*-
   2  *
   3  *************************************************************************
   4  *
   5  *  @copyright
   6  *  Copyright (C) 2009-2013, Intel Corporation
   7  *  All rights reserved.
   8  *
   9  *  @copyright
  10  *  Redistribution and use in source and binary forms, with or without
  11  *  modification, are permitted provided that the following conditions
  12  *  are met:
  13  *
  14  *    * Redistributions of source code must retain the above copyright
  15  *      notice, this list of conditions and the following disclaimer.
  16  *    * Redistributions in binary form must reproduce the above copyright
  17  *      notice, this list of conditions and the following disclaimer in
  18  *      the documentation and/or other materials provided with the
  19  *      distribution.
  20  *    * Neither the name of Intel Corporation nor the names of its
  21  *      contributors may be used to endorse or promote products derived
  22  *      from this software without specific prior written permission.
  23  *
  24  *  @copyright
  25  *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  26  *  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  27  *  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  28  *  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  29  *  HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  30  *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  31  *  BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
  32  *  OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  33  *  AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  34  *  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
  35  *  WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  36  *  POSSIBILITY OF SUCH DAMAGE.
  37  **************************************************************************/
  38
  39 #include "worker_mutex.h"
  40 #include "bug.h"
  41 #include "os.h"
  42 #include "stats.h"
  43
  44 /* m->lock == 1 means that mutex M is locked */
  45 #define TRY_ACQUIRE(m) (__cilkrts_xchg(&(m)->lock, 1) == 0)
  46
  47 /* ICC 11.1+ understands release semantics and generates an
  48    ordinary store with a software memory barrier. */
  49 #if __ICC >= 1110
  50 #define RELEASE(m) __sync_lock_release(&(m)->lock)
  51 #else
  52 #define RELEASE(m) __cilkrts_xchg(&(m)->lock, 0)
  53 #endif
  54
  55 void __cilkrts_mutex_init(struct mutex *m)
  56 {
  57     m->owner = 0;
  58
  59     // Use a simple assignment so Inspector doesn't bug us about the
  60     // interlocked exchange doing a read of an uninitialized variable.
  61     // By definition there can't be a race when we're initializing the
  62     // lock...
  63     m->lock = 0;
  64 }
  65
  66 void __cilkrts_mutex_lock(__cilkrts_worker *w, struct mutex *m)
  67 {
  68     int count;
  69     const int maxspin = 1000; /* SWAG */
  70
  71     NOTE_INTERVAL(w, INTERVAL_MUTEX_LOCK);
  72     if (!TRY_ACQUIRE(m)) {
  73         START_INTERVAL(w, INTERVAL_MUTEX_LOCK_SPINNING);
  74         count = 0;
  75         do {
  76             do {
  77                 __cilkrts_short_pause();
  78                 if (++count >= maxspin) {
  79                     STOP_INTERVAL(w, INTERVAL_MUTEX_LOCK_SPINNING);
  80                     START_INTERVAL(w, INTERVAL_MUTEX_LOCK_YIELDING);
  81                     /* let the OS reschedule every once in a while */
  82                     __cilkrts_yield();
  83                     STOP_INTERVAL(w, INTERVAL_MUTEX_LOCK_YIELDING);
  84                     START_INTERVAL(w, INTERVAL_MUTEX_LOCK_SPINNING);
  85                     count = 0;
  86                 }
  87             } while (m->lock != 0);
  88         } while (!TRY_ACQUIRE(m));
  89         STOP_INTERVAL(w, INTERVAL_MUTEX_LOCK_SPINNING);
  90     }
  91
  92     CILK_ASSERT(m->owner == 0);
  93     m->owner = w;
  94 }
  95
  96 int __cilkrts_mutex_trylock(__cilkrts_worker *w, struct mutex *m)
  97 {
  98     NOTE_INTERVAL(w, INTERVAL_MUTEX_TRYLOCK);
  99     if (TRY_ACQUIRE(m)) {
 100         CILK_ASSERT(m->owner == 0);
 101         m->owner = w;
 102         return 1;
 103     } else {
 104         return 0;
 105     }
 106 }
 107
 108 void __cilkrts_mutex_unlock(__cilkrts_worker *w, struct mutex *m)
 109 {
 110     CILK_ASSERT(m->owner == w);
 111     m->owner = 0;
 112     RELEASE(m);
 113 }
 114
 115 void __cilkrts_mutex_destroy(__cilkrts_worker *w, struct mutex *m)
 116 {
 117     (void)w; /* unused */
 118     (void)m; /* unused */
 119 }
 120
 121 /* End worker_mutex.c */