1 files changed, 20 insertions, 8 deletions

diff --git a/rts/sm/GC.c b/rts/sm/GC.c
index 3b65219927..928f4448d3 100644
--- a/rts/sm/GC.c
+++ b/rts/sm/GC.c
@@ -338,6 +338,13 @@ GarbageCollect (rtsBool force_major_gc,
       }
   } else {
       scavenge_capability_mut_lists(gct->cap);
+      for (n = 0; n < n_capabilities; n++) {
+          if (gc_threads[n]->idle) {
+              markCapability(mark_root, gct, &capabilities[n],
+                             rtsTrue/*don't mark sparks*/);
+              scavenge_capability_mut_lists(&capabilities[n]);
+          }
+      }
   }
 
   // follow roots from the CAF list (used by GHCi)
@@ -401,7 +408,11 @@ GarbageCollect (rtsBool force_major_gc,
           pruneSparkQueue(&capabilities[n]);
       }
   } else {
-      pruneSparkQueue(gct->cap);
+      for (n = 0; n < n_capabilities; n++) {
+          if (n == cap->no || gc_threads[n]->idle) {
+              pruneSparkQueue(&capabilities[n]);
+         }
+      }
   }
 #endif
 
@@ -808,6 +819,7 @@ new_gc_thread (nat n, gc_thread *t)
 #endif
 
     t->thread_index = n;
+    t->idle = rtsFalse;
     t->free_blocks = NULL;
     t->gc_count = 0;
 
@@ -1114,7 +1126,7 @@ waitForGcThreads (Capability *cap USED_IF_THREADS)
 
     while(retry) {
         for (i=0; i < n_threads; i++) {
-            if (i == me) continue;
+            if (i == me || gc_threads[i]->idle) continue;
             if (gc_threads[i]->wakeup != GC_THREAD_STANDING_BY) {
                 prodCapability(&capabilities[i], cap->running_task);
             }
@@ -1122,7 +1134,7 @@ waitForGcThreads (Capability *cap USED_IF_THREADS)
         for (j=0; j < 10; j++) {
             retry = rtsFalse;
             for (i=0; i < n_threads; i++) {
-                if (i == me) continue;
+                if (i == me || gc_threads[i]->idle) continue;
                 write_barrier();
                 interruptCapability(&capabilities[i]);
                 if (gc_threads[i]->wakeup != GC_THREAD_STANDING_BY) {
@@ -1154,8 +1166,8 @@ wakeup_gc_threads (nat me USED_IF_THREADS)
     if (n_gc_threads == 1) return;
 
     for (i=0; i < n_gc_threads; i++) {
-        if (i == me) continue;
-	inc_running();
+        if (i == me || gc_threads[i]->idle) continue;
+        inc_running();
         debugTrace(DEBUG_gc, "waking up gc thread %d", i);
         if (gc_threads[i]->wakeup != GC_THREAD_STANDING_BY) barf("wakeup_gc_threads");
 
@@ -1178,7 +1190,7 @@ shutdown_gc_threads (nat me USED_IF_THREADS)
     if (n_gc_threads == 1) return;
 
     for (i=0; i < n_gc_threads; i++) {
-        if (i == me) continue;
+        if (i == me || gc_threads[i]->idle) continue;
         while (gc_threads[i]->wakeup != GC_THREAD_WAITING_TO_CONTINUE) { write_barrier(); }
     }
 #endif
@@ -1192,8 +1204,8 @@ releaseGCThreads (Capability *cap USED_IF_THREADS)
     const nat me = cap->no;
     nat i;
     for (i=0; i < n_threads; i++) {
-        if (i == me) continue;
-        if (gc_threads[i]->wakeup != GC_THREAD_WAITING_TO_CONTINUE) 
+        if (i == me || gc_threads[i]->idle) continue;
+        if (gc_threads[i]->wakeup != GC_THREAD_WAITING_TO_CONTINUE)
             barf("releaseGCThreads");
         
         gc_threads[i]->wakeup = GC_THREAD_INACTIVE;