Fix race condition in wakeupThreadOnCapability() (#2574)

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

diff --git a/rts/Capability.c b/rts/Capability.c
index 0f03621..1f1a1ae 100644 (file)
--- a/rts/Capability.c
+++ b/rts/Capability.c
@@ -540,57 +540,40 @@ yieldCapability (Capability** pCap, Task *task)
  * ------------------------------------------------------------------------- */
 
 void
-wakeupThreadOnCapability (Capability *cap, StgTSO *tso)
+wakeupThreadOnCapability (Capability *my_cap, 
+                          Capability *other_cap, 
+                          StgTSO *tso)
 {
-    ASSERT(tso->cap == cap);
-    ASSERT(tso->bound ? tso->bound->cap == cap : 1);
-    ASSERT_LOCK_HELD(&cap->lock);
+    ACQUIRE_LOCK(&other_cap->lock);
 
-    tso->cap = cap;
+    // ASSUMES: cap->lock is held (asserted in wakeupThreadOnCapability)
+    if (tso->bound) {
+       ASSERT(tso->bound->cap == tso->cap);
+       tso->bound->cap = other_cap;
+    }
+    tso->cap = other_cap;
+
+    ASSERT(tso->bound ? tso->bound->cap == other_cap : 1);
 
-    if (cap->running_task == NULL) {
+    if (other_cap->running_task == NULL) {
        // nobody is running this Capability, we can add our thread
        // directly onto the run queue and start up a Task to run it.
-       appendToRunQueue(cap,tso);
 
-       // start it up
-       cap->running_task = myTask(); // precond for releaseCapability_()
-       trace(TRACE_sched, "resuming capability %d", cap->no);
-       releaseCapability_(cap);
+       other_cap->running_task = myTask(); 
+            // precond for releaseCapability_() and appendToRunQueue()
+
+       appendToRunQueue(other_cap,tso);
+
+       trace(TRACE_sched, "resuming capability %d", other_cap->no);
+       releaseCapability_(other_cap);
     } else {
-       appendToWakeupQueue(cap,tso);
+       appendToWakeupQueue(my_cap,other_cap,tso);
        // someone is running on this Capability, so it cannot be
        // freed without first checking the wakeup queue (see
        // releaseCapability_).
     }
-}
 
-void
-wakeupThreadOnCapability_lock (Capability *cap, StgTSO *tso)
-{
-    ACQUIRE_LOCK(&cap->lock);
-    migrateThreadToCapability (cap, tso);
-    RELEASE_LOCK(&cap->lock);
-}
-
-void
-migrateThreadToCapability (Capability *cap, StgTSO *tso)
-{
-    // ASSUMES: cap->lock is held (asserted in wakeupThreadOnCapability)
-    if (tso->bound) {
-       ASSERT(tso->bound->cap == tso->cap);
-       tso->bound->cap = cap;
-    }
-    tso->cap = cap;
-    wakeupThreadOnCapability(cap,tso);
-}
-
-void
-migrateThreadToCapability_lock (Capability *cap, StgTSO *tso)
-{
-    ACQUIRE_LOCK(&cap->lock);
-    migrateThreadToCapability (cap, tso);
-    RELEASE_LOCK(&cap->lock);
+    RELEASE_LOCK(&other_cap->lock);
 }
 
 /* ----------------------------------------------------------------------------
@@ -818,7 +801,7 @@ markSomeCapabilities (evac_fn evac, void *user, nat i0, nat delta)
        }
 
 #if defined(THREADED_RTS)
-        markSparkQueue (evac, user, cap);
+        traverseSparkQueue (evac, user, cap);
 #endif
     }