src/mongo/db/d_concurrency.cpp
ExcludeAllWrites::ExcludeAllWrites() : 
        lk(cc().lockStatus.excluder, d.writeExcluder), 
        gslk()
    {
        LOG(3) << "ExcludeAllWrites" << endl;
        wassert( !d.dbMutex.isWriteLocked() );
    }
/** Notes on d.writeExcluder
        we want to be able to block any attempted write while allowing reads; additionally 
        force non-greedy acquisition so that reads can continue -- 
        that is, disallow greediness of write lock acquisitions.  This is for that purpose.  The 
        #1 need is by groupCommitWithLimitedLocks() but useful elsewhere such as for lock and fsync.
    */
Notes on d.writeExcluder
we want to be able to block any attempted write while allowing reads; additionally
force non-greedy acquisition so that reads can continue
that is, disallow greediness of write lock acquisitions.  This is for that purpose.  The
1 need is by groupCommitWithLimitedLocks() but useful elsewhere such as for lock and fsync.
Notes on d . writeExcluder we want to be able to block any attempted write while allowing reads ; additionally force non - greedy acquisition so that reads can continue that is disallow greediness of write lock acquisitions . This is for that purpose . The 1 need is by groupCommitWithLimitedLocks () but useful elsewhere such as for lock and fsync .
ExcludeAllWrites::ExcludeAllWrites() : 
        lk(cc().lockStatus.excluder, d.writeExcluder), 
        gslk()
    {
        LOG(3) << "ExcludeAllWrites" << endl;
        wassert( !d.dbMutex.isWriteLocked() );
    }
ExcludeAllWrites :: ExcludeAllWrites ( ) : lk ( cc ( ) . lockStatus . excluder , d . writeExcluder ) , gslk ( ) { LOG ( 3 ) << " " << endl ; wassert ( ! d . dbMutex . isWriteLocked ( ) ) ; }
Notes on d.writeExcluder
we want to be able to block any attempted write while allowing reads; additionally
force non-greedy acquisition so that reads can continue 
that is, disallow greediness of write lock acquisitions.
Notes on d . writeExcluder we want to be able to block any attempted write while allowing reads ; additionally force non - greedy acquisition so that reads can continue that is disallow greediness of write lock acquisitions .