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/* 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
#if BOOST_VERSION >= 103500
#include <boost/thread/shared_mutex.hpp>
#undef assert
#define assert xassert
#endif
namespace mongo {
/* mutex time stats */
class MutexInfo {
unsigned long long start, enter, timeLocked; // all in microseconds
int locked;
public:
MutexInfo() : 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;
}
};
#if BOOST_VERSION >= 103500
//#if 0
class MongoMutex {
MutexInfo _minfo;
boost::shared_mutex _m;
ThreadLocalValue<int> _state;
public:
/**
* @return
* > 0 write lock
* = 0 no lock
* < 0 read lock
*/
int getState(){ return _state.get(); }
void assertWriteLocked() { assert( _state.get() > 0 ); }
bool atLeastReadLocked() { return _state.get() != 0; }
void assertAtLeastReadLocked() { assert(atLeastReadLocked()); }
void lock() {
DEV cout << "LOCK" << endl;
int s = _state.get();
if( s > 0 ) {
_state.set(s+1);
return;
}
massert("internal error: locks are not upgradeable", s == 0 );
_state.set(1);
_m.lock();
_minfo.entered();
}
void unlock() {
DEV cout << "UNLOCK" << endl;
int s = _state.get();
if( s > 1 ) {
_state.set(s-1);
return;
}
assert( s == 1 );
_state.set(0);
_minfo.leaving();
_m.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);
_m.lock_shared();
}
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; }
};
#else
/* this will be for old versions of boost */
class MongoMutex {
MutexInfo _minfo;
boost::recursive_mutex m;
public:
MongoMutex() { }
void lock() {
#if BOOST_VERSION >= 103500
m.lock();
#else
boost::detail::thread::lock_ops<boost::recursive_mutex>::lock(m);
#endif
_minfo.entered();
}
void unlock() {
_minfo.leaving();
#if BOOST_VERSION >= 103500
m.unlock();
#else
boost::detail::thread::lock_ops<boost::recursive_mutex>::unlock(m);
#endif
}
void lock_shared() { lock(); }
void unlock_shared() { unlock(); }
MutexInfo& info() { return _minfo; }
void assertWriteLocked() {
assert( info().isLocked() );
}
void assertAtLeastReadLocked() {
assert( info().isLocked() );
}
bool atLeastReadLocked() { return info().isLocked(); }
int getState(){ return info().isLocked() ? 1 : 0; }
};
#endif
extern MongoMutex &dbMutex;
void dbunlocking_write();
void dbunlocking_read();
struct writelock {
writelock(const string& ns) {
dbMutex.lock();
}
~writelock() {
dbunlocking_write();
dbMutex.unlock();
}
};
struct readlock {
readlock(const string& ns) {
dbMutex.lock_shared();
}
~readlock() {
dbunlocking_read();
dbMutex.unlock_shared();
}
};
class mongolock {
bool _writelock;
public:
mongolock(bool write) : _writelock(write) {
if( _writelock ) {
dbMutex.lock();
}
else
dbMutex.lock_shared();
}
~mongolock() {
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("") { }
~dblock() {
}
};
// eliminate
inline void assertInWriteLock() { dbMutex.assertWriteLocked(); }
}
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