rts/Schedule: Eliminate data races on recent_activity

We cannot safely use relaxed atomics here.

3 files changed, 12 insertions, 12 deletions

diff --git a/rts/Capability.c b/rts/Capability.c
index 5ebe6c8b46..3031d283c4 100644
--- a/rts/Capability.c
+++ b/rts/Capability.c
@@ -85,7 +85,7 @@ STATIC_INLINE bool
 globalWorkToDo (void)
 {
     return RELAXED_LOAD(&sched_state) >= SCHED_INTERRUPTING
-        || recent_activity == ACTIVITY_INACTIVE; // need to check for deadlock
+      || RELAXED_LOAD(&recent_activity) == ACTIVITY_INACTIVE; // need to check for deadlock
 }
 #endif
 
diff --git a/rts/Schedule.c b/rts/Schedule.c
index a9ae7a4ce4..e8bb9c1bf0 100644
--- a/rts/Schedule.c
+++ b/rts/Schedule.c
@@ -440,7 +440,7 @@ run_thread:
     dirty_TSO(cap,t);
     dirty_STACK(cap,t->stackobj);
 
-    switch (recent_activity)
+    switch (SEQ_CST_LOAD(&recent_activity))
     {
     case ACTIVITY_DONE_GC: {
         // ACTIVITY_DONE_GC means we turned off the timer signal to
@@ -461,7 +461,7 @@ run_thread:
         // wakeUpRts().
         break;
     default:
-        recent_activity = ACTIVITY_YES;
+        SEQ_CST_STORE(&recent_activity, ACTIVITY_YES);
     }
 
     traceEventRunThread(cap, t);
@@ -939,7 +939,7 @@ scheduleDetectDeadlock (Capability **pcap, Task *task)
          * we won't eagerly start a full GC just because we don't have
          * any threads to run currently.
          */
-        if (recent_activity != ACTIVITY_INACTIVE) return;
+        if (SEQ_CST_LOAD(&recent_activity) != ACTIVITY_INACTIVE) return;
 #endif
         if (task->incall->tso && task->incall->tso->why_blocked == BlockedOnIOCompletion) return;
 
@@ -1880,14 +1880,14 @@ delete_threads_and_gc:
 
     traceSparkCounters(cap);
 
-    switch (recent_activity) {
+    switch (SEQ_CST_LOAD(&recent_activity)) {
     case ACTIVITY_INACTIVE:
         if (force_major) {
             // We are doing a GC because the system has been idle for a
             // timeslice and we need to check for deadlock.  Record the
             // fact that we've done a GC and turn off the timer signal;
             // it will get re-enabled if we run any threads after the GC.
-            recent_activity = ACTIVITY_DONE_GC;
+            SEQ_CST_STORE(&recent_activity, ACTIVITY_DONE_GC);
 #if !defined(PROFILING)
             stopTimer();
 #endif
@@ -1899,7 +1899,7 @@ delete_threads_and_gc:
         // the GC might have taken long enough for the timer to set
         // recent_activity = ACTIVITY_MAYBE_NO or ACTIVITY_INACTIVE,
         // but we aren't necessarily deadlocked:
-        recent_activity = ACTIVITY_YES;
+        SEQ_CST_STORE(&recent_activity, ACTIVITY_YES);
         break;
 
     case ACTIVITY_DONE_GC:
@@ -2701,7 +2701,7 @@ initScheduler(void)
 #endif
 
   sched_state    = SCHED_RUNNING;
-  recent_activity = ACTIVITY_YES;
+  SEQ_CST_STORE(&recent_activity, ACTIVITY_YES);
 
 
   /* Initialise the mutex and condition variables used by
diff --git a/rts/Timer.c b/rts/Timer.c
index 057cffc7c9..990eba6b05 100644
--- a/rts/Timer.c
+++ b/rts/Timer.c
@@ -106,16 +106,16 @@ handle_tick(int unused STG_UNUSED)
    * for threads that are deadlocked.  However, ensure we wait
    * at least interIdleGCWait (+RTS -Iw) between idle GCs.
    */
-  switch (recent_activity) {
+  switch (SEQ_CST_LOAD(&recent_activity)) {
   case ACTIVITY_YES:
-      recent_activity = ACTIVITY_MAYBE_NO;
+      SEQ_CST_STORE(&recent_activity, ACTIVITY_MAYBE_NO);
       idle_ticks_to_gc = RtsFlags.GcFlags.idleGCDelayTime /
                          RtsFlags.MiscFlags.tickInterval;
       break;
   case ACTIVITY_MAYBE_NO:
       if (idle_ticks_to_gc == 0 && inter_gc_ticks_to_gc == 0) {
           if (RtsFlags.GcFlags.doIdleGC) {
-              recent_activity = ACTIVITY_INACTIVE;
+              SEQ_CST_STORE(&recent_activity, ACTIVITY_INACTIVE);
               inter_gc_ticks_to_gc = RtsFlags.GcFlags.interIdleGCWait /
                                      RtsFlags.MiscFlags.tickInterval;
 #if defined(THREADED_RTS)
@@ -124,7 +124,7 @@ handle_tick(int unused STG_UNUSED)
               // the GC.
 #endif
           } else {
-              recent_activity = ACTIVITY_DONE_GC;
+              SEQ_CST_STORE(&recent_activity, ACTIVITY_DONE_GC);
               // disable timer signals (see #1623, #5991, #9105)
               // but only if we're not profiling (e.g. passed -h or -p RTS
               // flags). If we are profiling we need to keep the timer active