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Commit 8f8374d7 authored by Dan Stoza's avatar Dan Stoza
Browse files

DispSync: Actually wait forever 

When computeNextEventTimeLocked returns INT64_MAX (because there are
currently no listeners), wait until the condition variable is
signaled instead of waiting for a long timeout. Since the condition
variable timeout is specified using CLOCK_REALTIME behind the scenes,
we can receive false wakeups in the presence of large system clock
changes.

Bug: 28152577
Change-Id: I88dbab5d5d0776cb25dea76a4574db055b308fd1
parent 6328134d

services/surfaceflinger/DispSync.cpp

+10 −6
Original line number Diff line number Diff line
@@ -97,7 +97,6 @@ public: 
    virtual bool threadLoop() {

        status_t err;

        nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);

        nsecs_t nextEventTime = 0;



        while (true) {

            Vector<CallbackInvocation> callbackInvocations;
@@ -127,16 +126,21 @@ public: 
                    continue;

                }



                nextEventTime = computeNextEventTimeLocked(now);

                targetTime = nextEventTime;

                targetTime = computeNextEventTimeLocked(now);



                bool isWakeup = false;



                if (now < targetTime) {

                    if (kTraceDetailedInfo) ATRACE_NAME("DispSync waiting");



                    if (targetTime == INT64_MAX) {

                        ALOGV("[%s] Waiting forever", mName);

                        err = mCond.wait(mMutex);

                    } else {

                        ALOGV("[%s] Waiting until %" PRId64, mName,

                                ns2us(targetTime));

                    if (kTraceDetailedInfo) ATRACE_NAME("DispSync waiting");

                        err = mCond.waitRelative(mMutex, targetTime - now);

                    }



                    if (err == TIMED_OUT) {

                        isWakeup = true;