void TestEnqueue( int p ) {
REMARK("Testing task::enqueue for %d threads\n", p);
for(int mode=0;mode<3;++mode) {
tbb::task_scheduler_init init(p);
EnqueuedTask::nCompletedPairs = EnqueuedTask::nOrderedPairs = 0;
for(int i=0; i<nTracks; ++i) {
TaskTracks[i] = -1; // to accomodate for the starting call
EnqueuedTask::FireTwoTasks(TaskTracks+i);
}
ProgressMonitor pm;
tbb::tbb_thread thr( pm );
if(mode==1) {
// do some parallel work in the meantime
for(int i=0; i<10; i++) {
TaskGenerator& g = *new( tbb::task::allocate_root() ) TaskGenerator(2,5);
tbb::task::spawn_root_and_wait(g);
TimedYield( 1E-6 );
}
}
if( mode==2 ) {
// Additionally enqueue a bunch of empty tasks. The goal is to test that tasks
// allocated and enqueued by a thread are safe to use after the thread leaves TBB.
tbb::task* root = new (tbb::task::allocate_root()) tbb::empty_task;
root->set_ref_count(100);
for( int i=0; i<100; ++i )
tbb::task::enqueue( *new (root->allocate_child()) tbb::empty_task );
init.terminate(); // master thread deregistered
}
thr.join();
ASSERT(EnqueuedTask::nCompletedPairs==nTracks*PairsPerTrack, NULL);
ASSERT(EnqueuedTask::nOrderedPairs<EnqueuedTask::nCompletedPairs,
"all task pairs executed in enqueue order; de facto guarantee is too strong?");
}
}
void operator() ( ) {
int track_snapshot[nTracks];
int stall_count = 0, uneven_progress_count = 0, last_progress_mask = 0;
for(int i=0; i<nTracks; ++i)
track_snapshot[i]=0;
bool completed;
do {
// Yield repeatedly for at least 1 usec
TimedYield( 1E-6 );
int overall_progress = 0, progress_mask = 0;
const int all_progressed = (1<<nTracks) - 1;
completed = true;
for(int i=0; i<nTracks; ++i) {
int ti = TaskTracks[i];
int pi = ti-track_snapshot[i];
if( pi ) progress_mask |= 1<<i;
overall_progress += pi;
completed = completed && ti==PairsPerTrack;
track_snapshot[i]=ti;
}
// The constants in the next asserts are subjective and may need correction.
if( overall_progress )
stall_count=0;
else {
++stall_count;
// no progress; consider it dead.
ASSERT(stall_count < stall_threshold, "no progress on enqueued tasks; deadlock, or the machine is heavily oversubscribed?");
}
if( progress_mask==all_progressed || progress_mask^last_progress_mask ) {
uneven_progress_count = 0;
last_progress_mask = progress_mask;
}
else if ( overall_progress > 2 ) {
++uneven_progress_count;
// The threshold of 32 is 4x bigger than what was observed on a 8-core machine with oversubscription.
ASSERT_WARNING(uneven_progress_count < 32,
"some enqueued tasks seem stalling; no simultaneous progress, or the machine is oversubscribed? Investigate if repeated");
}
} while( !completed );
}