diff options
| -rw-r--r-- | rts/Capability.c | 27 | ||||
| -rw-r--r-- | rts/Capability.h | 3 | ||||
| -rw-r--r-- | rts/Schedule.c | 7 |
3 files changed, 35 insertions, 2 deletions
diff --git a/rts/Capability.c b/rts/Capability.c index 444532480d..0f03621003 100644 --- a/rts/Capability.c +++ b/rts/Capability.c @@ -40,6 +40,9 @@ Capability *capabilities = NULL; // locking, so we don't do that. Capability *last_free_capability; +/* GC indicator, in scope for the scheduler, init'ed to false */ +volatile StgWord waiting_for_gc = 0; + #if defined(THREADED_RTS) STATIC_INLINE rtsBool globalWorkToDo (void) @@ -276,6 +279,21 @@ releaseCapability_ (Capability* cap) return; } + /* if waiting_for_gc was the reason to release the cap: thread + comes from yieldCap->releaseAndQueueWorker. Unconditionally set + cap. free and return (see default after the if-protected other + special cases). Thread will wait on cond.var and re-acquire the + same cap after GC (GC-triggering cap. calls releaseCap and + enters the spare_workers case) + */ + if (waiting_for_gc) { + last_free_capability = cap; // needed? + trace(TRACE_sched | DEBUG_sched, + "GC pending, set capability %d free", cap->no); + return; + } + + // If the next thread on the run queue is a bound thread, // give this Capability to the appropriate Task. if (!emptyRunQueue(cap) && cap->run_queue_hd->bound) { @@ -453,7 +471,14 @@ yieldCapability (Capability** pCap, Task *task) // The fast path has no locking, if we don't enter this while loop - while ( cap->returning_tasks_hd != NULL || !anyWorkForMe(cap,task) ) { + while ( waiting_for_gc + /* i.e. another capability triggered HeapOverflow, is busy + getting capabilities (stopping their owning tasks) */ + || cap->returning_tasks_hd != NULL + /* cap reserved for another task */ + || !anyWorkForMe(cap,task) + /* cap/task have no work */ + ) { debugTrace(DEBUG_sched, "giving up capability %d", cap->no); // We must now release the capability and wait to be woken up diff --git a/rts/Capability.h b/rts/Capability.h index 959ab50b3e..f13afe2117 100644 --- a/rts/Capability.h +++ b/rts/Capability.h @@ -162,6 +162,9 @@ extern Capability *capabilities; // extern Capability *last_free_capability; +// GC indicator, in scope for the scheduler +extern volatile StgWord waiting_for_gc; + // Acquires a capability at a return point. If *cap is non-NULL, then // this is taken as a preference for the Capability we wish to // acquire. diff --git a/rts/Schedule.c b/rts/Schedule.c index 94aac6ccc4..1b5afefc4f 100644 --- a/rts/Schedule.c +++ b/rts/Schedule.c @@ -1405,7 +1405,8 @@ scheduleDoGC (Capability *cap, Task *task USED_IF_THREADS, rtsBool force_major) StgTSO *t; rtsBool heap_census; #ifdef THREADED_RTS - static volatile StgWord waiting_for_gc; + /* extern static volatile StgWord waiting_for_gc; + lives inside capability.c */ rtsBool was_waiting; nat i; #endif @@ -1422,6 +1423,10 @@ scheduleDoGC (Capability *cap, Task *task USED_IF_THREADS, rtsBool force_major) // the other tasks to sleep and stay asleep. // + /* Other capabilities are prevented from running yet more Haskell + threads if waiting_for_gc is set. Tested inside + yieldCapability() and releaseCapability() in Capability.c */ + was_waiting = cas(&waiting_for_gc, 0, 1); if (was_waiting) { do { |