Bug 1868744 - If JS engine triggered a GC slice, don't trigger another too soon from CCGCScheduler, r=jonco

Differential Revision: https://phabricator.services.mozilla.com/D195755

dom/base/CCGCScheduler.cpp

@@ -622,6 +622,16 @@ void CCGCScheduler::PokeMinorGC(JS::GCReason aReason) {
   EnsureGCRunner(0);
 }
 
+void CCGCScheduler::EnsureOrResetGCRunner() {
+  if (!mGCRunner) {
+    EnsureGCRunner(0);
+    return;
+  }
+
+  mGCRunner->ResetTimer(TimeDuration::FromMilliseconds(
+      StaticPrefs::javascript_options_gc_delay_interslice()));
+}
+
 void CCGCScheduler::EnsureGCRunner(TimeDuration aDelay) {
   if (mGCRunner) {
     return;

dom/base/CCGCScheduler.h

@@ -191,6 +191,10 @@ class CCGCScheduler {
    */
   void EnsureGCRunner(TimeDuration aDelay);
 
+  // If GCRunner isn't active, this calls EnsureGCRunner(0). Otherwise the timer
+  // is reset.
+  void EnsureOrResetGCRunner();
+
   void EnsureCCRunner(TimeDuration aDelay, TimeDuration aBudget);
 
   // State modification

dom/base/nsJSEnvironment.cpp

@@ -1873,7 +1873,7 @@ static void DOMGCSliceCallback(JSContext* aCx, JS::GCProgress aProgress,
         // If incremental GC wasn't triggered by GCTimerFired, we may not have a
         // runner to ensure all the slices are handled. So, create the runner
         // here.
-        sScheduler->EnsureGCRunner(0);
+        sScheduler->EnsureOrResetGCRunner();
       }
 
       if (sScheduler->IsCCNeeded(TimeStamp::Now(),

xpcom/threads/IdleTaskRunner.cpp

@@ -259,6 +259,11 @@ void IdleTaskRunner::SetTimerInternal(TimeDuration aDelay) {
   if (mTimerActive) {
     return;
   }
+  ResetTimer(aDelay);
+}
+
+void IdleTaskRunner::ResetTimer(TimeDuration aDelay) {
+  mTimerActive = false;
 
   if (!mTimer) {
     mTimer = NS_NewTimer();

xpcom/threads/IdleTaskRunner.h

@@ -69,8 +69,11 @@ class IdleTaskRunner {
   // period, or null if not running during idle time.
   void SetIdleDeadline(mozilla::TimeStamp aDeadline);
 
+  // If the timer is already active, SetTimer doesn't do anything.
   void SetTimer(TimeDuration aDelay, nsIEventTarget* aTarget);
 
+  void ResetTimer(TimeDuration aDelay);
+
   // Update the minimum idle time that this callback would be invoked for.
   void SetMinimumUsefulBudget(int64_t aMinimumUsefulBudget);