Enable DTrace on Solaris; based on a patch from Karel Gardas
[ghc.git] / rts / Messages.c
index 6a7c64d..5dec6c6 100644 (file)
@@ -28,8 +28,7 @@ void sendMessage(Capability *from_cap, Capability *to_cap, Message *msg)
 #ifdef DEBUG    
     {
         const StgInfoTable *i = msg->header.info;
-        if (i != &stg_MSG_WAKEUP_info &&
-            i != &stg_MSG_THROWTO_info &&
+        if (i != &stg_MSG_THROWTO_info &&
             i != &stg_MSG_BLACKHOLE_info &&
             i != &stg_MSG_TRY_WAKEUP_info &&
             i != &stg_IND_info && // can happen if a MSG_BLACKHOLE is revoked
@@ -71,21 +70,7 @@ executeMessage (Capability *cap, Message *m)
 loop:
     write_barrier(); // allow m->header to be modified by another thread
     i = m->header.info;
-    if (i == &stg_MSG_WAKEUP_info)
-    {
-        // the plan is to eventually get rid of these and use
-        // TRY_WAKEUP instead.
-        MessageWakeup *w = (MessageWakeup *)m;
-        StgTSO *tso = w->tso;
-        debugTraceCap(DEBUG_sched, cap, "message: wakeup thread %ld", 
-                      (lnat)tso->id);
-        ASSERT(tso->cap == cap);
-        ASSERT(tso->why_blocked == BlockedOnMsgWakeup);
-        ASSERT(tso->block_info.closure == (StgClosure *)m);
-        tso->why_blocked = NotBlocked;
-        appendToRunQueue(cap, tso);
-    }
-    else if (i == &stg_MSG_TRY_WAKEUP_info)
+    if (i == &stg_MSG_TRY_WAKEUP_info)
     {
         StgTSO *tso = ((MessageWakeup *)m)->tso;
         debugTraceCap(DEBUG_sched, cap, "message: try wakeup thread %ld", 
@@ -113,11 +98,13 @@ loop:
         r = throwToMsg(cap, t);
 
         switch (r) {
-        case THROWTO_SUCCESS:
+        case THROWTO_SUCCESS: {
             // this message is done
-            unlockClosure((StgClosure*)m, &stg_MSG_NULL_info);
-            tryWakeupThread(cap, t->source);
+            StgTSO *source = t->source;
+            doneWithMsgThrowTo(t);
+            tryWakeupThread(cap, source);
             break;
+        }
         case THROWTO_BLOCKED:
             // unlock the message
             unlockClosure((StgClosure*)m, &stg_MSG_THROWTO_info);
@@ -176,7 +163,7 @@ nat messageBlackHole(Capability *cap, MessageBlackHole *msg)
     const StgInfoTable *info;
     StgClosure *p;
     StgBlockingQueue *bq;
-    StgClosure *bh = msg->bh;
+    StgClosure *bh = UNTAG_CLOSURE(msg->bh);
     StgTSO *owner;
 
     debugTraceCap(DEBUG_sched, cap, "message: thread %d blocking on blackhole %p", 
@@ -190,6 +177,7 @@ nat messageBlackHole(Capability *cap, MessageBlackHole *msg)
     // all.
     if (info != &stg_BLACKHOLE_info && 
         info != &stg_CAF_BLACKHOLE_info && 
+        info != &__stg_EAGER_BLACKHOLE_info &&
         info != &stg_WHITEHOLE_info) {
         // if it is a WHITEHOLE, then a thread is in the process of
         // trying to BLACKHOLE it.  But we know that it was once a
@@ -198,9 +186,12 @@ nat messageBlackHole(Capability *cap, MessageBlackHole *msg)
         return 0;
     }
 
-    // we know at this point that the closure 
+    // The blackhole must indirect to a TSO, a BLOCKING_QUEUE, an IND,
+    // or a value.
 loop:
-    p = ((StgInd*)bh)->indirectee;
+    // NB. VOLATILE_LOAD(), because otherwise gcc hoists the load
+    // and turns this into an infinite loop.
+    p = UNTAG_CLOSURE((StgClosure*)VOLATILE_LOAD(&((StgInd*)bh)->indirectee));
     info = p->header.info;
 
     if (info == &stg_IND_info)
@@ -214,7 +205,7 @@ loop:
 
     else if (info == &stg_TSO_info)
     {
-        owner = deRefTSO((StgTSO *)p);
+        owner = (StgTSO*)p;
 
 #ifdef THREADED_RTS
         if (owner->cap != cap) {
@@ -244,7 +235,21 @@ loop:
         bq->link = owner->bq;
         owner->bq = bq;
         dirty_TSO(cap, owner); // we modified owner->bq
-        
+
+        // If the owner of the blackhole is currently runnable, then
+        // bump it to the front of the run queue.  This gives the
+        // blocked-on thread a little boost which should help unblock
+        // this thread, and may avoid a pile-up of other threads
+        // becoming blocked on the same BLACKHOLE (#3838).
+        //
+        // NB. we check to make sure that the owner is not the same as
+        // the current thread, since in that case it will not be on
+        // the run queue.
+        if (owner->why_blocked == NotBlocked && owner->id != msg->tso->id) {
+            removeFromRunQueue(cap, owner);
+            pushOnRunQueue(cap,owner);
+        }
+
         // point to the BLOCKING_QUEUE from the BLACKHOLE
         write_barrier(); // make the BQ visible
         ((StgInd*)bh)->indirectee = (StgClosure *)bq;
@@ -262,7 +267,7 @@ loop:
 
         ASSERT(bq->bh == bh);
 
-        owner = deRefTSO(bq->owner);
+        owner = bq->owner;
 
         ASSERT(owner != END_TSO_QUEUE);
 
@@ -280,15 +285,64 @@ loop:
 
         if (info == &stg_BLOCKING_QUEUE_CLEAN_info) {
             bq->header.info = &stg_BLOCKING_QUEUE_DIRTY_info;
-            recordClosureMutated(cap,bq);
+            recordClosureMutated(cap,(StgClosure*)bq);
         }
 
         debugTraceCap(DEBUG_sched, cap, "thread %d blocked on thread %d", 
                       (lnat)msg->tso->id, (lnat)owner->id);
 
+        // See above, #3838
+        if (owner->why_blocked == NotBlocked && owner->id != msg->tso->id) {
+            removeFromRunQueue(cap, owner);
+            pushOnRunQueue(cap,owner);
+        }
+
         return 1; // blocked
     }
     
     return 0; // not blocked
 }
 
+// A shorter version of messageBlackHole(), that just returns the
+// owner (or NULL if the owner cannot be found, because the blackhole
+// has been updated in the meantime).
+
+StgTSO * blackHoleOwner (StgClosure *bh)
+{
+    const StgInfoTable *info;
+    StgClosure *p;
+
+    info = bh->header.info;
+
+    if (info != &stg_BLACKHOLE_info &&
+        info != &stg_CAF_BLACKHOLE_info && 
+        info != &__stg_EAGER_BLACKHOLE_info &&
+        info != &stg_WHITEHOLE_info) {
+        return NULL;
+    }
+
+    // The blackhole must indirect to a TSO, a BLOCKING_QUEUE, an IND,
+    // or a value.
+loop:
+    // NB. VOLATILE_LOAD(), because otherwise gcc hoists the load
+    // and turns this into an infinite loop.
+    p = UNTAG_CLOSURE((StgClosure*)VOLATILE_LOAD(&((StgInd*)bh)->indirectee));
+    info = p->header.info;
+
+    if (info == &stg_IND_info) goto loop;
+
+    else if (info == &stg_TSO_info)
+    {
+        return (StgTSO*)p;
+    }
+    else if (info == &stg_BLOCKING_QUEUE_CLEAN_info || 
+             info == &stg_BLOCKING_QUEUE_DIRTY_info)
+    {
+        StgBlockingQueue *bq = (StgBlockingQueue *)p;
+        return bq->owner;
+    }
+    
+    return NULL; // not blocked
+}
+
+