Verified Commit efee8978 authored by Jon Coppeard's avatar Jon Coppeard Committed by ma1
Browse files

Bug 1828024 - Require the helper thread lock in the GC helper thread count getter r=sfink 

This makes us take a lock to read this state (we already lock when writing it).

Also it adds a release assert in case something goes wrong with the thread
count calculations, as a crash is preferable to the potential deadlock.

Differential Revision: https://phabricator.services.mozilla.com/D181257
parent 30d19aa0

js/src/gc/GC.cpp

+7 −2
Original line number Diff line number Diff line
@@ -1331,6 +1331,11 @@ void GCRuntime::assertNoMarkingWork() const { 
}

#endif



static size_t GetGCParallelThreadCount() {

  AutoLockHelperThreadState lock;

  return HelperThreadState().getGCParallelThreadCount(lock);

}



bool GCRuntime::updateMarkersVector() {

  MOZ_ASSERT(helperThreadCount >= 1,

             "There must always be at least one mark task");
@@ -1339,8 +1344,8 @@ bool GCRuntime::updateMarkersVector() { 


  // Limit worker count to number of GC parallel tasks that can run

  // concurrently, otherwise one thread can deadlock waiting on another.

  size_t targetCount = std::min(markingWorkerCount(),

                                HelperThreadState().getGCParallelThreadCount());

  size_t targetCount =

      std::min(markingWorkerCount(), GetGCParallelThreadCount());



  if (markers.length() > targetCount) {

    return markers.resize(targetCount);

js/src/gc/ParallelMarking.cpp

+4 −0
Original line number Diff line number Diff line
@@ -103,6 +103,10 @@ bool ParallelMarker::markOneColor(MarkColor color, SliceBudget& sliceBudget) { 
  {

    AutoLockHelperThreadState lock;



    // There should always be enough parallel tasks to run our marking work.

    MOZ_RELEASE_ASSERT(HelperThreadState().getGCParallelThreadCount(lock) >=

                       workerCount());



    for (size_t i = 0; i < workerCount(); i++) {

      gc->startTask(*tasks[i], lock);

    }

js/src/vm/HelperThreadState.h

+4 −2
Original line number Diff line number Diff line
@@ -333,9 +333,11 @@ class GlobalHelperThreadState { 


  GCParallelTaskList& gcParallelWorklist() { return gcParallelWorklist_; }



  size_t getGCParallelThreadCount() const { return gcParallelThreadCount; }

  size_t getGCParallelThreadCount(const AutoLockHelperThreadState& lock) const {

    return gcParallelThreadCount;

  }

  void setGCParallelThreadCount(size_t count,

                                const AutoLockHelperThreadState&) {

                                const AutoLockHelperThreadState& lock) {

    MOZ_ASSERT(count >= 1);

    MOZ_ASSERT(count <= threadCount);

    gcParallelThreadCount = count;