FIX (partially) #2703: bug in stack overflow handling when inside block

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

diff --git a/rts/Schedule.c b/rts/Schedule.c
index a41dd67..626c097 100644 (file)
--- a/rts/Schedule.c
+++ b/rts/Schedule.c
@@ -89,11 +89,6 @@ StgTSO *blackhole_queue = NULL;
  */
 rtsBool blackholes_need_checking = rtsFalse;
 
-/* flag set by signal handler to precipitate a context switch
- * LOCK: none (just an advisory flag)
- */
-int context_switch = 0;
-
 /* flag that tracks whether we have done any execution in this time slice.
  * LOCK: currently none, perhaps we should lock (but needs to be
  * updated in the fast path of the scheduler).
@@ -155,7 +150,7 @@ static rtsBool scheduleGetRemoteWork(Capability *cap);
 static void scheduleSendPendingMessages(void);
 static void scheduleActivateSpark(Capability *cap);
 #endif
-static void schedulePostRunThread(StgTSO *t);
+static void schedulePostRunThread(Capability *cap, StgTSO *t);
 static rtsBool scheduleHandleHeapOverflow( Capability *cap, StgTSO *t );
 static void scheduleHandleStackOverflow( Capability *cap, Task *task, 
                                         StgTSO *t);
@@ -504,7 +499,7 @@ schedule (Capability *initialCapability, Task *task)
      */
     if (RtsFlags.ConcFlags.ctxtSwitchTicks == 0
        && !emptyThreadQueues(cap)) {
-       context_switch = 1;
+       cap->context_switch = 1;
     }
         
 run_thread:
@@ -627,7 +622,7 @@ run_thread:
     CCCS = CCS_SYSTEM;
 #endif
     
-    schedulePostRunThread(t);
+    schedulePostRunThread(cap,t);
 
     t = threadStackUnderflow(task,t);
 
@@ -1069,7 +1064,7 @@ scheduleGetRemoteWork(Capability *cap)
  * ------------------------------------------------------------------------- */
 
 static void
-schedulePostRunThread (StgTSO *t)
+schedulePostRunThread (Capability *cap, StgTSO *t)
 {
     // We have to be able to catch transactions that are in an
     // infinite loop as a result of seeing an inconsistent view of
@@ -1090,8 +1085,7 @@ schedulePostRunThread (StgTSO *t)
             // ATOMICALLY_FRAME, aborting the (nested)
             // transaction, and saving the stack of any
             // partially-evaluated thunks on the heap.
-            throwToSingleThreaded_(&capabilities[0], t, 
-                                   NULL, rtsTrue, NULL);
+            throwToSingleThreaded_(cap, t, NULL, rtsTrue, NULL);
             
             ASSERT(get_itbl((StgClosure *)t->sp)->type == ATOMICALLY_FRAME);
         }
@@ -1179,12 +1173,12 @@ scheduleHandleHeapOverflow( Capability *cap, StgTSO *t )
               "--<< thread %ld (%s) stopped: HeapOverflow",
               (long)t->id, whatNext_strs[t->what_next]);
 
-    if (context_switch) {
+    if (cap->context_switch) {
         // Sometimes we miss a context switch, e.g. when calling
         // primitives in a tight loop, MAYBE_GC() doesn't check the
         // context switch flag, and we end up waiting for a GC.
         // See #1984, and concurrent/should_run/1984
-        context_switch = 0;
+        cap->context_switch = 0;
         addToRunQueue(cap,t);
     } else {
         pushOnRunQueue(cap,t);
@@ -1234,7 +1228,7 @@ scheduleHandleYield( Capability *cap, StgTSO *t, nat prev_what_next )
     // the CPU because the tick always arrives during GC).  This way
     // penalises threads that do a lot of allocation, but that seems
     // better than the alternative.
-    context_switch = 0;
+    cap->context_switch = 0;
     
     /* put the thread back on the run queue.  Then, if we're ready to
      * GC, check whether this is the last task to stop.  If so, wake
@@ -1435,6 +1429,7 @@ scheduleDoGC (Capability *cap, Task *task USED_IF_THREADS, rtsBool force_major)
        return cap;  // NOTE: task->cap might have changed here
     }
 
+    setContextSwitches();
     for (i=0; i < n_capabilities; i++) {
        debugTrace(DEBUG_sched, "ready_to_gc, grabbing all the capabilies (%d/%d)", i, n_capabilities);
        if (cap != &capabilities[i]) {
@@ -1445,7 +1440,6 @@ scheduleDoGC (Capability *cap, Task *task USED_IF_THREADS, rtsBool force_major)
            // all the Capabilities, but even so it's a slightly
            // unsavoury invariant.
            task->cap = pcap;
-           context_switch = 1;
            waitForReturnCapability(&pcap, task);
            if (pcap != &capabilities[i]) {
                barf("scheduleDoGC: got the wrong capability");
@@ -1954,7 +1948,6 @@ initScheduler(void)
 
   blackhole_queue   = END_TSO_QUEUE;
 
-  context_switch = 0;
   sched_state    = SCHED_RUNNING;
   recent_activity = ACTIVITY_YES;
 
@@ -2132,10 +2125,17 @@ threadStackOverflow(Capability *cap, StgTSO *tso)
   }
 
   /* Try to double the current stack size.  If that takes us over the
-   * maximum stack size for this thread, then use the maximum instead.
-   * Finally round up so the TSO ends up as a whole number of blocks.
+   * maximum stack size for this thread, then use the maximum instead
+   * (that is, unless we're already at or over the max size and we
+   * can't raise the StackOverflow exception (see above), in which
+   * case just double the size). Finally round up so the TSO ends up as
+   * a whole number of blocks.
    */
-  new_stack_size = stg_min(tso->stack_size * 2, tso->max_stack_size);
+  if (tso->stack_size >= tso->max_stack_size) {
+      new_stack_size = tso->stack_size * 2;
+  } else { 
+      new_stack_size = stg_min(tso->stack_size * 2, tso->max_stack_size);
+  }
   new_tso_size   = (lnat)BLOCK_ROUND_UP(new_stack_size * sizeof(W_) + 
                                       TSO_STRUCT_SIZE)/sizeof(W_);
   new_tso_size = round_to_mblocks(new_tso_size);  /* Be MBLOCK-friendly */
@@ -2192,7 +2192,7 @@ static StgTSO *
 threadStackUnderflow (Task *task STG_UNUSED, StgTSO *tso)
 {
     bdescr *bd, *new_bd;
-    lnat new_tso_size_w, tso_size_w;
+    lnat free_w, tso_size_w;
     StgTSO *new_tso;
 
     tso_size_w = tso_sizeW(tso);
@@ -2207,19 +2207,19 @@ threadStackUnderflow (Task *task STG_UNUSED, StgTSO *tso)
     // while we are moving the TSO:
     lockClosure((StgClosure *)tso);
 
-    new_tso_size_w = round_to_mblocks(tso_size_w/2);
-
-    debugTrace(DEBUG_sched, "thread %ld: reducing TSO size from %lu words to %lu",
-               (long)tso->id, tso_size_w, new_tso_size_w);
+    // this is the number of words we'll free
+    free_w = round_to_mblocks(tso_size_w/2);
 
     bd = Bdescr((StgPtr)tso);
-    new_bd = splitLargeBlock(bd, new_tso_size_w / BLOCK_SIZE_W);
-    new_bd->free = bd->free;
+    new_bd = splitLargeBlock(bd, free_w / BLOCK_SIZE_W);
     bd->free = bd->start + TSO_STRUCT_SIZEW;
 
     new_tso = (StgTSO *)new_bd->start;
     memcpy(new_tso,tso,TSO_STRUCT_SIZE);
-    new_tso->stack_size = new_tso_size_w - TSO_STRUCT_SIZEW;
+    new_tso->stack_size = new_bd->free - new_tso->stack;
+
+    debugTrace(DEBUG_sched, "thread %ld: reducing TSO size from %lu words to %lu",
+               (long)tso->id, tso_size_w, tso_sizeW(new_tso));
 
     tso->what_next = ThreadRelocated;
     tso->_link = new_tso; // no write barrier reqd: same generation
@@ -2247,7 +2247,7 @@ void
 interruptStgRts(void)
 {
     sched_state = SCHED_INTERRUPTING;
-    context_switch = 1;
+    setContextSwitches();
     wakeUpRts();
 }