1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
|
/* Copyright (c) 2010, Google Inc.
* All rights reserved.
*
* 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 Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* 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
* OWNER 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.
*/
// The OS-specific header included below must provide two calls:
// base::internal::SpinLockDelay() and base::internal::SpinLockWake().
// See spinlock_internal.h for the spec of SpinLockWake().
// void SpinLockDelay(volatile Atomic32 *w, int32 value, int loop)
// SpinLockDelay() generates an apprproate spin delay on iteration "loop" of a
// spin loop on location *w, whose previously observed value was "value".
// SpinLockDelay() may do nothing, may yield the CPU, may sleep a clock tick,
// or may wait for a delay that can be truncated by a call to SpinlockWake(w).
// In all cases, it must return in bounded time even if SpinlockWake() is not
// called.
#include "base/spinlock_internal.h"
#if defined(_WIN32)
#include "base/spinlock_win32-inl.h"
#elif defined(__linux__) && !defined(__native_client__)
#include "base/spinlock_linux-inl.h"
#else
#include "base/spinlock_posix-inl.h"
#endif
namespace base {
namespace internal {
// See spinlock_internal.h for spec.
int32 SpinLockWait(volatile Atomic32 *w, int n,
const SpinLockWaitTransition trans[]) {
int32 v;
bool done = false;
for (int loop = 0; !done; loop++) {
v = base::subtle::Acquire_Load(w);
int i;
for (i = 0; i != n && v != trans[i].from; i++) {
}
if (i == n) {
SpinLockDelay(w, v, loop); // no matching transition
} else if (trans[i].to == v || // null transition
base::subtle::Acquire_CompareAndSwap(w, v, trans[i].to) == v) {
done = trans[i].done;
}
}
return v;
}
} // namespace internal
} // namespace base
|
