Fix another subtle shutdown deadlock

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

diff --git a/rts/Schedule.c b/rts/Schedule.c
index 499cf77..aedd6b7 100644 (file)
--- a/rts/Schedule.c
+++ b/rts/Schedule.c
@@ -340,7 +340,14 @@ schedule (Capability *initialCapability, Task *task)
 #endif
        /* scheduleDoGC() deletes all the threads */
        cap = scheduleDoGC(cap,task,rtsFalse);
-       break;
+
+        // after scheduleDoGC(), we must be shutting down.  Either some
+        // other Capability did the final GC, or we did it above,
+        // either way we can fall through to the SCHED_SHUTTING_DOWN
+        // case now.
+        ASSERT(sched_state == SCHED_SHUTTING_DOWN);
+        // fall through
+
     case SCHED_SHUTTING_DOWN:
        debugTrace(DEBUG_sched, "SCHED_SHUTTING_DOWN");
        // If we are a worker, just exit.  If we're a bound thread
@@ -1467,6 +1474,13 @@ scheduleDoGC (Capability *cap, Task *task USED_IF_THREADS, rtsBool force_major)
     nat i;
 #endif
 
+    if (sched_state == SCHED_SHUTTING_DOWN) {
+        // The final GC has already been done, and the system is
+        // shutting down.  We'll probably deadlock if we try to GC
+        // now.
+        return cap;
+    }
+
 #ifdef THREADED_RTS
     // In order to GC, there must be no threads running Haskell code.
     // Therefore, the GC thread needs to hold *all* the capabilities,