static rtsBool
scheduleHandleYield( Capability *cap, StgTSO *t, nat prev_what_next )
{
- // Reset the context switch flag. We don't do this just before
- // running the thread, because that would mean we would lose ticks
- // during GC, which can lead to unfair scheduling (a thread hogs
- // the CPU because the tick always arrives during GC). This way
- // penalises threads that do a lot of allocation, but that seems
- // better than the alternative.
- cap->context_switch = 0;
-
/* put the thread back on the run queue. Then, if we're ready to
* GC, check whether this is the last task to stop. If so, wake
* up the GC thread. getThread will block during a GC until the
* GC is finished.
*/
-#ifdef DEBUG
- if (t->what_next != prev_what_next) {
- debugTrace(DEBUG_sched,
- "--<< thread %ld (%s) stopped to switch evaluators",
- (long)t->id, what_next_strs[t->what_next]);
- }
-#endif
-
+
ASSERT(t->_link == END_TSO_QUEUE);
// Shortcut if we're just switching evaluators: don't bother
// doing stack squeezing (which can be expensive), just run the
// thread.
- if (t->what_next != prev_what_next) {
+ if (cap->context_switch == 0 && t->what_next != prev_what_next) {
+ debugTrace(DEBUG_sched,
+ "--<< thread %ld (%s) stopped to switch evaluators",
+ (long)t->id, what_next_strs[t->what_next]);
return rtsTrue;
}
+ // Reset the context switch flag. We don't do this just before
+ // running the thread, because that would mean we would lose ticks
+ // during GC, which can lead to unfair scheduling (a thread hogs
+ // the CPU because the tick always arrives during GC). This way
+ // penalises threads that do a lot of allocation, but that seems
+ // better than the alternative.
+ cap->context_switch = 0;
+
IF_DEBUG(sanity,
//debugBelch("&& Doing sanity check on yielding TSO %ld.", t->id);
checkTSO(t));