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Bug Fix: Fixed situation in which the memory block is left unlocked

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This commit is contained in:
Itay Grudev 2020-09-08 23:15:17 +01:00
parent a136c734c9
commit 81052d9a61
1 changed files with 17 additions and 14 deletions
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31
singleapplication.cpp
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@ -76,7 +76,6 @@ SingleApplication::SingleApplication( int &argc, char *argv[], bool allowSeconda
// Initialize the shared memory block // Initialize the shared memory block
d->memory->lock(); d->memory->lock();
d->initializeMemoryBlock(); d->initializeMemoryBlock();
d->memory->unlock();
} else { } else {
// Attempt to attach to the memory segment // Attempt to attach to the memory segment
if( ! d->memory->attach() ){ if( ! d->memory->attach() ){
@ -85,6 +84,7 @@ SingleApplication::SingleApplication( int &argc, char *argv[], bool allowSeconda
delete d; delete d;
::exit( EXIT_FAILURE ); ::exit( EXIT_FAILURE );
} }
d->memory->lock();
} }
auto *inst = static_cast<InstancesInfo*>( d->memory->data() ); auto *inst = static_cast<InstancesInfo*>( d->memory->data() );
@ -93,24 +93,27 @@ SingleApplication::SingleApplication( int &argc, char *argv[], bool allowSeconda
// Make sure the shared memory block is initialised and in consistent state // Make sure the shared memory block is initialised and in consistent state
while( true ){ while( true ){
d->memory->lock(); // If the shared memory block's checksum is valid continue
if( d->blockChecksum() == inst->checksum ) break;
if( d->blockChecksum() == inst->checksum ) break; // If more than 5s have elapsed, assume the primary instance crashed and
// assume it's position
if( time.elapsed() > 5000 ){
qWarning() << "SingleApplication: Shared memory block has been in an inconsistent state from more than 5s. Assuming primary instance failure.";
d->initializeMemoryBlock();
}
if( time.elapsed() > 5000 ){ // Otherwise wait for a random period and try again. The random sleep here
qWarning() << "SingleApplication: Shared memory block has been in an inconsistent state from more than 5s. Assuming primary instance failure."; // limits the probability of a collision between two racing apps and
d->initializeMemoryBlock(); // allows the app to initialise faster
} d->memory->unlock();
d->memory->unlock();
// Random sleep here limits the probability of a collision between two racing apps
#if QT_VERSION >= QT_VERSION_CHECK( 5, 10, 0 ) #if QT_VERSION >= QT_VERSION_CHECK( 5, 10, 0 )
QThread::sleep( QRandomGenerator::global()->bounded( 8u, 18u )); QThread::sleep( QRandomGenerator::global()->bounded( 8u, 18u ));
#else #else
qsrand( QDateTime::currentMSecsSinceEpoch() % std::numeric_limits<uint>::max() ); qsrand( QDateTime::currentMSecsSinceEpoch() % std::numeric_limits<uint>::max() );
QThread::sleep( 8 + static_cast <unsigned long>( static_cast <float>( qrand() ) / RAND_MAX * 10 )); QThread::sleep( 8 + static_cast <unsigned long>( static_cast <float>( qrand() ) / RAND_MAX * 10 ));
#endif #endif
d->memory->lock();
} }
if( inst->primary == false ){ if( inst->primary == false ){