blob: 6e30a4cb00c0f5f07944d87098e5f20a8072b639 (
plain)
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
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
|
// spin_lock.cpp
/* Copyright 2009 10gen Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "mongo/pch.h" // todo eliminate this include
#include "mongo/util/concurrency/spin_lock.h"
#include <time.h>
namespace mongo {
SpinLock::~SpinLock() {
#if defined(_WIN32)
DeleteCriticalSection(&_cs);
#elif defined(__USE_XOPEN2K)
pthread_spin_destroy(&_lock);
#endif
}
SpinLock::SpinLock()
#if defined(_WIN32)
{ InitializeCriticalSectionAndSpinCount(&_cs, 4000); }
#elif defined(__USE_XOPEN2K)
{ pthread_spin_init( &_lock , 0 ); }
#elif defined(__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4)
: _locked( false ) { }
#else
: _mutex( "SpinLock" ) { }
#endif
#if defined(__USE_XOPEN2K)
NOINLINE_DECL void SpinLock::_lk() {
/**
* this is designed to perform close to the default spin lock
* the reason for the mild insanity is to prevent horrible performance
* when contention spikes
* it allows spinlocks to be used in many more places
* which is good because even with this change they are about 8x faster on linux
*/
for ( int i=0; i<1000; i++ ) {
if ( pthread_spin_trylock( &_lock ) == 0 )
return;
#if defined(__i386__) || defined(__x86_64__)
asm volatile ( "pause" ) ; // maybe trylock does this; just in case.
#endif
}
for ( int i=0; i<1000; i++ ) {
if ( pthread_spin_trylock( &_lock ) == 0 )
return;
pthread_yield();
}
struct timespec t;
t.tv_sec = 0;
t.tv_nsec = 5000000;
while ( pthread_spin_trylock( &_lock ) != 0 ) {
nanosleep(&t, NULL);
}
}
#elif defined(__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4)
void SpinLock::lock() {
// fast path
if (!_locked && !__sync_lock_test_and_set(&_locked, true)) {
return;
}
// wait for lock
int wait = 1000;
while ((wait-- > 0) && (_locked)) {
#if defined(__i386__) || defined(__x86_64__)
asm volatile ( "pause" ) ;
#endif
}
// if failed to grab lock, sleep
struct timespec t;
t.tv_sec = 0;
t.tv_nsec = 5000000;
while (__sync_lock_test_and_set(&_locked, true)) {
nanosleep(&t, NULL);
}
}
#endif
bool SpinLock::isfast() {
#if defined(_WIN32) || defined(__USE_XOPEN2K) || defined(__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4)
return true;
#else
return false;
#endif
}
} // namespace mongo
|
