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Commit 90055aa0 authored by Ady Abraham's avatar Ady Abraham
Browse files

FenceTimeline: Fix a potential race condition 

FenceTimeline::updateSignalTimes checks if mQueue is empty without
grabbing the lock. This can lead a situaltion that a threads calls
pop() on an empty queue.

Test: boot
Bug: 132735340
Change-Id: I3007bfc1161797cb4d853506bb354e820bc9105d
parent 3f8312b5

libs/ui/FenceTime.cpp

+1 −1
Original line number Diff line number Diff line
@@ -279,8 +279,8 @@ void FenceTimeline::push(const std::shared_ptr<FenceTime>& fence) { 
}



void FenceTimeline::updateSignalTimes() {

    while (!mQueue.empty()) {

    std::lock_guard<std::mutex> lock(mMutex);

    while (!mQueue.empty()) {

        std::shared_ptr<FenceTime> fence = mQueue.front().lock();

        if (!fence) {

            // The shared_ptr no longer exists and no one cares about the

libs/ui/include/ui/FenceTime.h

+2 −1
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ 


#include <ui/Fence.h>

#include <utils/Flattenable.h>

#include <utils/Mutex.h>

#include <utils/Timers.h>



#include <atomic>
@@ -159,7 +160,7 @@ public: 


private:

    mutable std::mutex mMutex;

    std::queue<std::weak_ptr<FenceTime>> mQueue;

    std::queue<std::weak_ptr<FenceTime>> mQueue GUARDED_BY(mMutex);

};



// Used by test code to create or get FenceTimes for a given Fence.