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
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
|
// @file mutex.h
/* 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.
*/
#pragma once
#include <map>
#include <set>
namespace mongo {
extern bool __destroyingStatics;
class mutex;
// only used on _DEBUG builds:
class MutexDebugger {
typedef const char * mid; // mid = mutex ID
typedef map<mid,int> Preceeding;
map< mid, int > maxNest;
boost::thread_specific_ptr< Preceeding > us;
map< mid, set<mid> > followers;
boost::mutex &x;
unsigned magic;
public:
// set these to create an assert that
// b must never be locked before a
// so
// a.lock(); b.lock(); is fine
// b.lock(); alone is fine too
// only checked on _DEBUG builds.
string a,b;
void aBreakPoint(){}
void programEnding();
MutexDebugger();
void entering(mid m) {
if( magic != 0x12345678 ) return;
Preceeding *_preceeding = us.get();
if( _preceeding == 0 )
us.reset( _preceeding = new Preceeding() );
Preceeding &preceeding = *_preceeding;
if( a == m ) {
aBreakPoint();
if( preceeding[b.c_str()] ) {
cout << "mutex problem " << b << " was locked before " << a << endl;
assert(false);
}
}
preceeding[m]++;
if( preceeding[m] > 1 ) {
// recursive re-locking.
if( preceeding[m] > maxNest[m] )
maxNest[m] = preceeding[m];
return;
}
bool failed = false;
string err;
{
boost::mutex::scoped_lock lk(x);
followers[m];
for( Preceeding::iterator i = preceeding.begin(); i != preceeding.end(); i++ ) {
if( m != i->first && i->second > 0 ) {
followers[i->first].insert(m);
if( followers[m].count(i->first) != 0 ){
failed = true;
stringstream ss;
mid bad = i->first;
ss << "mutex problem" <<
"\n when locking " << m <<
"\n " << bad << " was already locked and should not be."
"\n set a and b above to debug.\n";
stringstream q;
for( Preceeding::iterator i = preceeding.begin(); i != preceeding.end(); i++ ) {
if( i->first != m && i->first != bad && i->second > 0 )
q << " " << i->first << '\n';
}
string also = q.str();
if( !also.empty() )
ss << "also locked before " << m << " in this thread (no particular order):\n" << also;
err = ss.str();
break;
}
}
}
}
if( failed ) {
cout << err << endl;
assert( 0 );
}
}
void leaving(mid m) {
if( magic != 0x12345678 ) return;
Preceeding& preceeding = *us.get();
preceeding[m]--;
if( preceeding[m] < 0 ) {
cout << "ERROR: lock count for " << m << " is " << preceeding[m] << endl;
assert( preceeding[m] >= 0 );
}
}
};
extern MutexDebugger &mutexDebugger;
// If you create a local static instance of this class, that instance will be destroyed
// before all global static objects are destroyed, so __destroyingStatics will be set
// to true before the global static variables are destroyed.
class StaticObserver : boost::noncopyable {
public:
~StaticObserver() { __destroyingStatics = true; }
};
// On pthread systems, it is an error to destroy a mutex while held. Static global
// mutexes may be held upon shutdown in our implementation, and this way we avoid
// destroying them.
class mutex : boost::noncopyable {
public:
#if defined(_DEBUG)
const char *_name;
#endif
#if defined(_DEBUG)
mutex(const char *name)
: _name(name)
#else
mutex(const char *)
#endif
{
_m = new boost::mutex();
}
~mutex() {
if( !__destroyingStatics ) {
delete _m;
}
}
class scoped_lock : boost::noncopyable {
#if defined(_DEBUG)
mongo::mutex *mut;
#endif
public:
scoped_lock( mongo::mutex &m ) : _l( m.boost() ) {
#if defined(_DEBUG)
mut = &m;
mutexDebugger.entering(mut->_name);
#endif
}
~scoped_lock() {
#if defined(_DEBUG)
mutexDebugger.leaving(mut->_name);
#endif
}
boost::mutex::scoped_lock &boost() { return _l; }
private:
boost::mutex::scoped_lock _l;
};
private:
boost::mutex &boost() { return *_m; }
boost::mutex *_m;
};
typedef mutex::scoped_lock scoped_lock;
typedef boost::recursive_mutex::scoped_lock recursive_scoped_lock;
}
|
