libcilkrts/runtime/worker_mutex.c

   1 /* worker_mutex.c                  -*-C-*-
   2  *
   3  *************************************************************************
   4  *
   5  *  Copyright (C) 2009-2016, Intel Corporation
   6  *  All rights reserved.
   7  *
   8  *  Redistribution and use in source and binary forms, with or without
   9  *  modification, are permitted provided that the following conditions
  10  *  are met:
  11  *
  12  *    * Redistributions of source code must retain the above copyright
  13  *      notice, this list of conditions and the following disclaimer.
  14  *    * Redistributions in binary form must reproduce the above copyright
  15  *      notice, this list of conditions and the following disclaimer in
  16  *      the documentation and/or other materials provided with the
  17  *      distribution.
  18  *    * Neither the name of Intel Corporation nor the names of its
  19  *      contributors may be used to endorse or promote products derived
  20  *      from this software without specific prior written permission.
  21  *
  22  *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  23  *  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  24  *  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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  30  *  AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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  34  *
  35  *  *********************************************************************
  36  *
  37  *  PLEASE NOTE: This file is a downstream copy of a file mainitained in
  38  *  a repository at cilkplus.org. Changes made to this file that are not
  39  *  submitted through the contribution process detailed at
  40  *  http://www.cilkplus.org/submit-cilk-contribution will be lost the next
  41  *  time that a new version is released. Changes only submitted to the
  42  *  GNU compiler collection or posted to the git repository at
  43  *  https://bitbucket.org/intelcilkruntime/intel-cilk-runtime.git are
  44  *  not tracked.
  45  *
  46  *  We welcome your contributions to this open source project. Thank you
  47  *  for your assistance in helping us improve Cilk Plus.
  48  **************************************************************************/
  49
  50 #include "worker_mutex.h"
  51 #include "bug.h"
  52 #include "os.h"
  53 #include "stats.h"
  54
  55 /* m->lock == 1 means that mutex M is locked */
  56 #define TRY_ACQUIRE(m) (__cilkrts_xchg(&(m)->lock, 1) == 0)
  57
  58 /* ICC 11.1+ understands release semantics and generates an
  59    ordinary store with a software memory barrier. */
  60 #if __ICC >= 1110
  61 #define RELEASE(m) __sync_lock_release(&(m)->lock)
  62 #else
  63 #define RELEASE(m) __cilkrts_xchg(&(m)->lock, 0)
  64 #endif
  65
  66 void __cilkrts_mutex_init(struct mutex *m)
  67 {
  68     m->owner = 0;
  69
  70     // Use a simple assignment so Inspector doesn't bug us about the
  71     // interlocked exchange doing a read of an uninitialized variable.
  72     // By definition there can't be a race when we're initializing the
  73     // lock...
  74     m->lock = 0;
  75 }
  76
  77 void __cilkrts_mutex_lock(__cilkrts_worker *w, struct mutex *m)
  78 {
  79     int count;
  80     const int maxspin = 1000; /* SWAG */
  81
  82     NOTE_INTERVAL(w, INTERVAL_MUTEX_LOCK);
  83     if (!TRY_ACQUIRE(m)) {
  84         START_INTERVAL(w, INTERVAL_MUTEX_LOCK_SPINNING);
  85         count = 0;
  86         do {
  87             do {
  88                 __cilkrts_short_pause();
  89                 if (++count >= maxspin) {
  90                     STOP_INTERVAL(w, INTERVAL_MUTEX_LOCK_SPINNING);
  91                     START_INTERVAL(w, INTERVAL_MUTEX_LOCK_YIELDING);
  92                     /* let the OS reschedule every once in a while */
  93                     __cilkrts_yield();
  94                     STOP_INTERVAL(w, INTERVAL_MUTEX_LOCK_YIELDING);
  95                     START_INTERVAL(w, INTERVAL_MUTEX_LOCK_SPINNING);
  96                     count = 0;
  97                 }
  98             } while (m->lock != 0);
  99         } while (!TRY_ACQUIRE(m));
 100         STOP_INTERVAL(w, INTERVAL_MUTEX_LOCK_SPINNING);
 101     }
 102
 103     CILK_ASSERT(m->owner == 0);
 104     m->owner = w;
 105 }
 106
 107 int __cilkrts_mutex_trylock(__cilkrts_worker *w, struct mutex *m)
 108 {
 109     NOTE_INTERVAL(w, INTERVAL_MUTEX_TRYLOCK);
 110     if (TRY_ACQUIRE(m)) {
 111         CILK_ASSERT(m->owner == 0);
 112         m->owner = w;
 113         return 1;
 114     } else {
 115         return 0;
 116     }
 117 }
 118
 119 void __cilkrts_mutex_unlock(__cilkrts_worker *w, struct mutex *m)
 120 {
 121     CILK_ASSERT(m->owner == w);
 122     m->owner = 0;
 123     RELEASE(m);
 124 }
 125
 126 void __cilkrts_mutex_destroy(__cilkrts_worker *w, struct mutex *m)
 127 {
 128     (void)w; /* unused */
 129     (void)m; /* unused */
 130 }
 131
 132 /* End worker_mutex.c */