rts: Mitigate races in capability interruption logic

1 files changed, 6 insertions, 6 deletions

diff --git a/rts/Schedule.c b/rts/Schedule.c
index 8af5a51d51..3796ae63de 100644
--- a/rts/Schedule.c
+++ b/rts/Schedule.c
@@ -405,7 +405,7 @@ schedule (Capability *initialCapability, Task *task)
      */
     if (RtsFlags.ConcFlags.ctxtSwitchTicks == 0
         && !emptyThreadQueues(cap)) {
-        cap->context_switch = 1;
+        RELAXED_STORE(&cap->context_switch, 1);
     }
 
 run_thread:
@@ -432,7 +432,7 @@ run_thread:
 #endif
 
     // reset the interrupt flag before running Haskell code
-    cap->interrupt = 0;
+    RELAXED_STORE(&cap->interrupt, false);
 
     cap->in_haskell = true;
     cap->idle = 0;
@@ -1132,12 +1132,12 @@ schedulePostRunThread (Capability *cap, StgTSO *t)
 static bool
 scheduleHandleHeapOverflow( Capability *cap, StgTSO *t )
 {
-    if (cap->r.rHpLim == NULL || cap->context_switch) {
+    if (cap->r.rHpLim == NULL || RELAXED_LOAD(&cap->context_switch)) {
         // Sometimes we miss a context switch, e.g. when calling
         // primitives in a tight loop, MAYBE_GC() doesn't check the
         // context switch flag, and we end up waiting for a GC.
         // See #1984, and concurrent/should_run/1984
-        cap->context_switch = 0;
+        RELAXED_STORE(&cap->context_switch, 0);
         appendToRunQueue(cap,t);
     } else {
         pushOnRunQueue(cap,t);
@@ -1238,8 +1238,8 @@ scheduleHandleYield( Capability *cap, StgTSO *t, uint32_t prev_what_next )
     // the CPU because the tick always arrives during GC).  This way
     // penalises threads that do a lot of allocation, but that seems
     // better than the alternative.
-    if (cap->context_switch != 0) {
-        cap->context_switch = 0;
+    if (RELAXED_LOAD(&cap->context_switch) != 0) {
+        RELAXED_STORE(&cap->context_switch, 0);
         appendToRunQueue(cap,t);
     } else {
         pushOnRunQueue(cap,t);