/usr/include/mongo/util/concurrency/mutexdebugger.h is in mongodb-dev 1:2.4.9-1ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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 | // @file mutexdebugger.h
/**
* Copyright (C) 2012 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#pragma once
#include "mongo/client/undef_macros.h"
#include <iostream>
#include <map>
#include <set>
#include <sstream>
#include <string>
#include "boost/thread/mutex.hpp"
#include "mongo/client/redef_macros.h"
#include "mongo/util/assert_util.h"
namespace mongo {
/** only used on _DEBUG builds.
MutexDebugger checks that we always acquire locks for multiple mutexes in a consistent (acyclic) order.
If we were inconsistent we could deadlock.
*/
class MutexDebugger {
typedef const char * mid; // mid = mutex ID
typedef std::map<mid,int> Preceeding;
std::map< mid, int > maxNest;
boost::thread_specific_ptr< Preceeding > us;
std::map< mid, std::set<mid> > followers;
boost::mutex &x;
unsigned magic;
void aBreakPoint() { } // for debugging
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.
std::string a,b;
/** outputs some diagnostic info on mutexes (on _DEBUG builds) */
void programEnding();
MutexDebugger();
std::string currentlyLocked() const {
Preceeding *_preceeding = us.get();
if( _preceeding == 0 )
return "";
Preceeding &preceeding = *_preceeding;
std::stringstream q;
for( Preceeding::const_iterator i = preceeding.begin(); i != preceeding.end(); i++ ) {
if( i->second > 0 )
q << " " << i->first << ' ' << i->second << '\n';
}
return q.str();
}
void entering(mid m) {
if( this == 0 || m == 0 ) return;
verify( magic == 0x12345678 );
Preceeding *_preceeding = us.get();
if( _preceeding == 0 )
us.reset( _preceeding = new Preceeding() );
Preceeding &preceeding = *_preceeding;
if( a == m ) {
aBreakPoint();
if( preceeding[b.c_str()] ) {
std::cout << "****** MutexDebugger error! warning " << b << " was locked before " << a << std::endl;
verify(false);
}
}
preceeding[m]++;
if( preceeding[m] > 1 ) {
// recursive re-locking.
if( preceeding[m] > maxNest[m] )
maxNest[m] = preceeding[m];
return;
}
bool failed = false;
std::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;
std::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";
std::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';
}
std::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 ) {
std::cout << err << std::endl;
verify( 0 );
}
}
void leaving(mid m) {
if( this == 0 || m == 0 ) return; // still in startup pre-main()
Preceeding& preceeding = *us.get();
preceeding[m]--;
if( preceeding[m] < 0 ) {
std::cout << "ERROR: lock count for " << m << " is " << preceeding[m] << std::endl;
verify( preceeding[m] >= 0 );
}
}
};
extern MutexDebugger &mutexDebugger;
}
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