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
__cilkrts_mutex_init(struct mutex * m)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
__cilkrts_mutex_lock(__cilkrts_worker * w,struct mutex * m)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
__cilkrts_mutex_trylock(__cilkrts_worker * w,struct mutex * m)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
__cilkrts_mutex_unlock(__cilkrts_worker * w,struct mutex * m)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
__cilkrts_mutex_destroy(__cilkrts_worker * w,struct mutex * m)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 */
122