Commit 1120322b authored by Simon Marlow's avatar Simon Marlow
Browse files

fix a rather subtle SMP bug in anyWorkForMe()

parent 4dfe2a24
......@@ -53,19 +53,23 @@ globalWorkToDo (void)
anyWorkForMe( Capability *cap, Task *task )
// If the run queue is not empty, then we only wake up the guy who
// can run the thread at the head, even if there is some other
// reason for this task to run (eg. interrupted=rtsTrue).
if (!emptyRunQueue(cap)) {
if (cap->run_queue_hd->bound == NULL) {
return (task->tso == NULL);
} else {
return (cap->run_queue_hd->bound == task);
} else if (task->tso == NULL && !emptySparkPoolCap(cap)) {
return rtsTrue;
if (task->tso != NULL) {
// A bound task only runs if its thread is on the run queue of
// the capability on which it was woken up. Otherwise, we
// can't be sure that we have the right capability: the thread
// might be woken up on some other capability, and task->cap
// could change under our feet.
return (!emptyRunQueue(cap) && cap->run_queue_hd->bound == task);
} else {
// A vanilla worker task runs if either (a) there is a
// lightweight thread at the head of the run queue, or (b)
// there are sparks to execute, or (c) there is some other
// global condition to check, such as threads blocked on
// blackholes.
return ((!emptyRunQueue(cap) && cap->run_queue_hd->bound == NULL)
|| !emptySparkPoolCap(cap)
|| globalWorkToDo());
return globalWorkToDo();
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