Fix #3156: ensure preconditions of splitLargeBlock()

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

diff --git a/rts/Schedule.c b/rts/Schedule.c
index 9792302..f376286 100644 (file)
--- a/rts/Schedule.c
+++ b/rts/Schedule.c
@@ -2235,9 +2235,7 @@ exitScheduler(
 {
     Task *task = NULL;
 
-    ACQUIRE_LOCK(&sched_mutex);
     task = newBoundTask();
-    RELEASE_LOCK(&sched_mutex);
 
     // If we haven't killed all the threads yet, do it now.
     if (sched_state < SCHED_SHUTTING_DOWN) {
@@ -2301,9 +2299,7 @@ performGC_(rtsBool force_major)
     // We must grab a new Task here, because the existing Task may be
     // associated with a particular Capability, and chained onto the 
     // suspended_ccalling_tasks queue.
-    ACQUIRE_LOCK(&sched_mutex);
     task = newBoundTask();
-    RELEASE_LOCK(&sched_mutex);
 
     waitForReturnCapability(&task->cap,task);
     scheduleDoGC(task->cap,task,force_major);
@@ -2440,9 +2436,16 @@ threadStackUnderflow (Task *task STG_UNUSED, StgTSO *tso)
 
     tso_size_w = tso_sizeW(tso);
 
-    if (tso_size_w < MBLOCK_SIZE_W || 
+    if (tso_size_w < MBLOCK_SIZE_W ||
+          // TSO is less than 2 mblocks (since the first mblock is
+          // shorter than MBLOCK_SIZE_W)
+        (tso_size_w - BLOCKS_PER_MBLOCK*BLOCK_SIZE_W) % MBLOCK_SIZE_W != 0 ||
+          // or TSO is not a whole number of megablocks (ensuring
+          // precondition of splitLargeBlock() below)
         (nat)(tso->stack + tso->stack_size - tso->sp) > tso->stack_size / 4) 
+          // or stack is using more than 1/4 of the available space
     {
+        // then do nothing
         return tso;
     }