Don't Terminate the ticker thread (#3748)

[ghc-hetmet.git] / rts / Schedule.c

diff --git a/rts/Schedule.c b/rts/Schedule.c
index cfdb392..c61bbc7 100644 (file)
--- a/rts/Schedule.c
+++ b/rts/Schedule.c
@@ -463,7 +463,11 @@ run_thread:
         if (prev == ACTIVITY_DONE_GC) {
             startTimer();
         }
-    } else {
+    } else if (recent_activity != ACTIVITY_INACTIVE) {
+        // If we reached ACTIVITY_INACTIVE, then don't reset it until
+        // we've done the GC.  The thread running here might just be
+        // the IO manager thread that handle_tick() woke up via
+        // wakeUpRts().
         recent_activity = ACTIVITY_YES;
     }
 #endif
@@ -705,7 +709,7 @@ schedulePushWork(Capability *cap USED_IF_THREADS,
     Capability *free_caps[n_capabilities], *cap0;
     nat i, n_free_caps;
 
-    // migration can be turned off with +RTS -qg
+    // migration can be turned off with +RTS -qm
     if (!RtsFlags.ParFlags.migrate) return;
 
     // Check whether we have more threads on our run queue, or sparks
@@ -775,7 +779,6 @@ schedulePushWork(Capability *cap USED_IF_THREADS,
                    setTSOLink(cap, prev, t);
                    prev = t;
                } else {
-                   debugTrace(DEBUG_sched, "pushing thread %lu to capability %d", (unsigned long)t->id, free_caps[i]->no);
                    appendToRunQueue(free_caps[i],t);
 
             traceEventMigrateThread (cap, t, free_caps[i]->no);
@@ -1328,6 +1331,17 @@ scheduleHandleThreadFinished (Capability *cap STG_UNUSED, Task *task, StgTSO *t)
 #ifdef DEBUG
          removeThreadLabel((StgWord)task->tso->id);
 #endif
+
+          // We no longer consider this thread and task to be bound to
+          // each other.  The TSO lives on until it is GC'd, but the
+          // task is about to be released by the caller, and we don't
+          // want anyone following the pointer from the TSO to the
+          // defunct task (which might have already been
+          // re-used). This was a real bug: the GC updated
+          // tso->bound->tso which lead to a deadlock.
+          t->bound = NULL;
+          task->tso = NULL;
+
          return rtsTrue; // tells schedule() to return
       }
 
@@ -1937,6 +1951,7 @@ Capability *
 scheduleWaitThread (StgTSO* tso, /*[out]*/HaskellObj* ret, Capability *cap)
 {
     Task *task;
+    StgThreadID id;
 
     // We already created/initialised the Task
     task = cap->running_task;
@@ -1952,14 +1967,15 @@ scheduleWaitThread (StgTSO* tso, /*[out]*/HaskellObj* ret, Capability *cap)
 
     appendToRunQueue(cap,tso);
 
-    debugTrace(DEBUG_sched, "new bound thread (%lu)", (unsigned long)tso->id);
+    id = tso->id;
+    debugTrace(DEBUG_sched, "new bound thread (%lu)", (unsigned long)id);
 
     cap = schedule(cap,task);
 
     ASSERT(task->stat != NoStatus);
     ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
 
-    debugTrace(DEBUG_sched, "bound thread (%lu) finished", (unsigned long)task->tso->id);
+    debugTrace(DEBUG_sched, "bound thread (%lu) finished", (unsigned long)id);
     return cap;
 }
 
@@ -2089,7 +2105,8 @@ exitScheduler(
     if (sched_state < SCHED_SHUTTING_DOWN) {
        sched_state = SCHED_INTERRUPTING;
         waitForReturnCapability(&task->cap,task);
-       scheduleDoGC(task->cap,task,rtsFalse);    
+       scheduleDoGC(task->cap,task,rtsFalse);
+        ASSERT(task->tso == NULL);
         releaseCapability(task->cap);
     }
     sched_state = SCHED_SHUTTING_DOWN;
@@ -2099,6 +2116,7 @@ exitScheduler(
        nat i;
        
        for (i = 0; i < n_capabilities; i++) {
+            ASSERT(task->tso == NULL);
            shutdownCapability(&capabilities[i], task, wait_foreign);
        }
     }
@@ -2546,7 +2564,8 @@ raiseExceptionHelper (StgRegTable *reg, StgTSO *tso, StgClosure *exception)
                SET_HDR(raise_closure, &stg_raise_info, CCCS);
                raise_closure->payload[0] = exception;
            }
-           UPD_IND(((StgUpdateFrame *)p)->updatee,(StgClosure *)raise_closure);
+           UPD_IND(cap, ((StgUpdateFrame *)p)->updatee,
+                    (StgClosure *)raise_closure);
            p = next;
            continue;