/
concurrency.h
354 lines (305 loc) · 9.52 KB
/
concurrency.h
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/*
* Copyright (C) 2010 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/>.
*/
/* concurrency.h
mongod concurrency rules & notes will be placed here.
Mutex heirarchy (1 = "leaf")
name level
Logstream::mutex 1
ClientCursor::ccmutex 2
dblock 3
End func name with _inlock to indicate "caller must lock before calling".
*/
#pragma once
#include "../util/concurrency/rwlock.h"
#include "../util/mmap.h"
namespace mongo {
string sayClientState();
bool haveClient();
void curopWaitingForLock( int type );
void curopGotLock();
/* mutex time stats */
class MutexInfo {
unsigned long long start, enter, timeLocked; // all in microseconds
int locked;
public:
MutexInfo() : timeLocked(0) , locked(0) {
start = curTimeMicros64();
}
void entered() {
if ( locked == 0 )
enter = curTimeMicros64();
locked++;
assert( locked >= 1 );
}
void leaving() {
locked--;
assert( locked >= 0 );
if ( locked == 0 )
timeLocked += curTimeMicros64() - enter;
}
int isLocked() const {
return locked;
}
void getTimingInfo(unsigned long long &s, unsigned long long &tl) const {
s = start;
tl = timeLocked;
}
unsigned long long getTimeLocked() const {
return timeLocked;
}
};
class MongoMutex {
MutexInfo _minfo;
RWLock _m;
ThreadLocalValue<int> _state;
/* we use a separate TLS value for releasedEarly - that is ok as
our normal/common code path, we never even touch it.
*/
ThreadLocalValue<bool> _releasedEarly;
public:
MongoMutex(const char * name) : _m(name) { }
/**
* @return
* > 0 write lock
* = 0 no lock
* < 0 read lock
*/
int getState() { return _state.get(); }
bool isWriteLocked() { return getState() > 0; }
void assertWriteLocked() {
assert( getState() > 0 );
DEV assert( !_releasedEarly.get() );
}
bool atLeastReadLocked() { return _state.get() != 0; }
void assertAtLeastReadLocked() { assert(atLeastReadLocked()); }
bool _checkWriteLockAlready(){
//DEV cout << "LOCK" << endl;
DEV assert( haveClient() );
int s = _state.get();
if( s > 0 ) {
_state.set(s+1);
return true;
}
massert( 10293 , (string)"internal error: locks are not upgradeable: " + sayClientState() , s == 0 );
return false;
}
void lock() {
if ( _checkWriteLockAlready() )
return;
_state.set(1);
curopWaitingForLock( 1 );
_m.lock();
curopGotLock();
_minfo.entered();
MongoFile::lockAll();
}
bool lock_try( int millis ) {
if ( _checkWriteLockAlready() )
return true;
curopWaitingForLock( 1 );
bool got = _m.lock_try( millis );
curopGotLock();
if ( got ){
_minfo.entered();
_state.set(1);
MongoFile::lockAll();
}
return got;
}
void unlock() {
//DEV cout << "UNLOCK" << endl;
int s = _state.get();
if( s > 1 ) {
_state.set(s-1);
return;
}
if( s != 1 ) {
if( _releasedEarly.get() ) {
_releasedEarly.set(false);
return;
}
massert( 12599, "internal error: attempt to unlock when wasn't in a write lock", false);
}
MongoFile::unlockAll();
_state.set(0);
_minfo.leaving();
_m.unlock();
}
/* unlock (write lock), and when unlock() is called later,
be smart then and don't unlock it again.
*/
void releaseEarly() {
assert( getState() == 1 ); // must not be recursive
assert( !_releasedEarly.get() );
_releasedEarly.set(true);
unlock();
}
void lock_shared() {
//DEV cout << " LOCKSHARED" << endl;
int s = _state.get();
if( s ) {
if( s > 0 ) {
// already in write lock - just be recursive and stay write locked
_state.set(s+1);
return;
}
else {
// already in read lock - recurse
_state.set(s-1);
return;
}
}
_state.set(-1);
curopWaitingForLock( -1 );
_m.lock_shared();
curopGotLock();
}
bool lock_shared_try( int millis ) {
int s = _state.get();
if ( s ){
// we already have a lock, so no need to try
lock_shared();
return true;
}
bool got = _m.lock_shared_try( millis );
if ( got )
_state.set(-1);
return got;
}
void unlock_shared() {
//DEV cout << " UNLOCKSHARED" << endl;
int s = _state.get();
if( s > 0 ) {
assert( s > 1 ); /* we must have done a lock write first to have s > 1 */
_state.set(s-1);
return;
}
if( s < -1 ) {
_state.set(s+1);
return;
}
assert( s == -1 );
_state.set(0);
_m.unlock_shared();
}
MutexInfo& info() { return _minfo; }
};
extern MongoMutex &dbMutex;
inline void dbunlocking_write() { }
inline void dbunlocking_read() { }
struct writelock {
writelock(const string& ns) {
dbMutex.lock();
}
~writelock() {
DESTRUCTOR_GUARD(
dbunlocking_write();
dbMutex.unlock();
);
}
};
struct readlock {
readlock(const string& ns) {
dbMutex.lock_shared();
}
~readlock() {
DESTRUCTOR_GUARD(
dbunlocking_read();
dbMutex.unlock_shared();
);
}
};
struct readlocktry {
readlocktry( const string&ns , int tryms ){
_got = dbMutex.lock_shared_try( tryms );
}
~readlocktry() {
if ( _got ){
dbunlocking_read();
dbMutex.unlock_shared();
}
}
bool got() const { return _got; }
private:
bool _got;
};
struct writelocktry {
writelocktry( const string&ns , int tryms ){
_got = dbMutex.lock_try( tryms );
}
~writelocktry() {
if ( _got ){
dbunlocking_read();
dbMutex.unlock();
}
}
bool got() const { return _got; }
private:
bool _got;
};
struct readlocktryassert : public readlocktry {
readlocktryassert(const string& ns, int tryms) :
readlocktry(ns,tryms) {
uassert(13142, "timeout getting readlock", got());
}
};
/** assure we have at least a read lock - they key with this being
if you have a write lock, that's ok too.
*/
struct atleastreadlock {
atleastreadlock( const string& ns ){
_prev = dbMutex.getState();
if ( _prev == 0 )
dbMutex.lock_shared();
}
~atleastreadlock(){
if ( _prev == 0 )
dbMutex.unlock_shared();
}
private:
int _prev;
};
class mongolock {
bool _writelock;
public:
mongolock(bool write) : _writelock(write) {
if( _writelock ) {
dbMutex.lock();
}
else
dbMutex.lock_shared();
}
~mongolock() {
DESTRUCTOR_GUARD(
if( _writelock ) {
dbunlocking_write();
dbMutex.unlock();
} else {
dbunlocking_read();
dbMutex.unlock_shared();
}
);
}
/* this unlocks, does NOT upgrade. that works for our current usage */
void releaseAndWriteLock();
};
/* use writelock and readlock instead */
struct dblock : public writelock {
dblock() : writelock("") { }
};
// eliminate
inline void assertInWriteLock() { dbMutex.assertWriteLocked(); }
}