Make the running_finalizers flag task-local

Fixes a bug reported by Lennart Augustsson, whereby we could get an
incorrect error from the RTS about re-entry from a finalizer,

4 files changed, 23 insertions, 10 deletions

diff --git a/rts/RtsAPI.c b/rts/RtsAPI.c
index 6e6621841e..2479f2038a 100644
--- a/rts/RtsAPI.c
+++ b/rts/RtsAPI.c
@@ -538,7 +538,9 @@ rts_lock (void)
     Capability *cap;
     Task *task;
 
-    if (running_finalizers) {
+    task = newBoundTask();
+
+    if (task->running_finalizers) {
         errorBelch("error: a C finalizer called back into Haskell.\n"
                    "   This was previously allowed, but is disallowed in GHC 6.10.2 and later.\n"
                    "   To create finalizers that may call back into Haskell, use\n"
@@ -546,8 +548,6 @@ rts_lock (void)
         stg_exit(EXIT_FAILURE);
     }
 
-    task = newBoundTask();
-
     cap = NULL;
     waitForReturnCapability(&cap, task);
     return (Capability *)cap;
diff --git a/rts/Task.c b/rts/Task.c
index 9707251ca3..98f083c112 100644
--- a/rts/Task.c
+++ b/rts/Task.c
@@ -153,6 +153,7 @@ newTask (rtsBool worker)
     task->cap           = NULL;
     task->worker        = worker;
     task->stopped       = rtsFalse;
+    task->running_finalizers = rtsFalse;
     task->stat          = NoStatus;
     task->ret           = NULL;
     task->n_spare_incalls = 0;
diff --git a/rts/Task.h b/rts/Task.h
index c2b58f2c45..2e0a4b83fa 100644
--- a/rts/Task.h
+++ b/rts/Task.h
@@ -134,6 +134,9 @@ typedef struct Task_ {
     rtsBool    worker;          // == rtsTrue if this is a worker Task
     rtsBool    stopped;         // this task has stopped or exited Haskell
 
+    // So that we can detect when a finalizer illegally calls back into Haskell
+    rtsBool running_finalizers;
+
     SchedulerStatus  stat;      // return status
     StgClosure **    ret;       // return value
 
diff --git a/rts/Weak.c b/rts/Weak.c
index 94bead3752..5546514243 100644
--- a/rts/Weak.c
+++ b/rts/Weak.c
@@ -21,9 +21,6 @@
 
 StgWeak *weak_ptr_list;
 
-// So that we can detect when a finalizer illegally calls back into Haskell
-rtsBool running_finalizers = rtsFalse;
-
 void
 runCFinalizer(void *fn, void *ptr, void *env, StgWord flag)
 {
@@ -37,8 +34,12 @@ void
 runAllCFinalizers(StgWeak *list)
 {
     StgWeak *w;
+    Task *task;
 
-    running_finalizers = rtsTrue;
+    task = myTask();
+    if (task != NULL) {
+        task->running_finalizers = rtsTrue;
+    }
 
     for (w = list; w; w = w->link) {
 	StgArrWords *farr;
@@ -52,7 +53,9 @@ runAllCFinalizers(StgWeak *list)
 	                  farr->payload[3]);
     }
 
-    running_finalizers = rtsFalse;
+    if (task != NULL) {
+        task->running_finalizers = rtsFalse;
+    }
 }
 
 /*
@@ -78,8 +81,12 @@ scheduleFinalizers(Capability *cap, StgWeak *list)
     StgMutArrPtrs *arr;
     StgWord size;
     nat n, i;
+    Task *task;
 
-    running_finalizers = rtsTrue;
+    task = myTask();
+    if (task != NULL) {
+        task->running_finalizers = rtsTrue;
+    }
 
     // count number of finalizers, and kill all the weak pointers first...
     n = 0;
@@ -114,7 +121,9 @@ scheduleFinalizers(Capability *cap, StgWeak *list)
 	SET_HDR(w, &stg_DEAD_WEAK_info, w->header.prof.ccs);
     }
 	
-    running_finalizers = rtsFalse;
+    if (task != NULL) {
+        task->running_finalizers = rtsFalse;
+    }
 
     // No finalizers to run?
     if (n == 0) return;