Commit 4753cf73 authored by's avatar
Browse files

Capability stopping when waiting for GC

parent 297b05a9
......@@ -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)
globalWorkToDo (void)
......@@ -276,6 +279,21 @@ releaseCapability_ (Capability* cap)
/* 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);
// 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
......@@ -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.
......@@ -1405,7 +1405,8 @@ scheduleDoGC (Capability *cap, Task *task USED_IF_THREADS, rtsBool force_major)
StgTSO *t;
rtsBool heap_census;
static volatile StgWord waiting_for_gc;
/* extern static volatile StgWord waiting_for_gc;
lives inside capability.c */
rtsBool was_waiting;
nat i;
......@@ -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 {
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