commit f8734e014d3a5596be2edc6ee85dbda7589bb889
author Dominik Laskowski <domlaskowski@google.com> Fri Aug 26 09:06:59 2022 -0700
committer Dominik Laskowski <domlaskowski@google.com> Thu Sep 08 08:48:21 2022 -0700
tree fd30cadac81cfd364477ef0c9247fc8ea7b32dbf
parent f2595446af5d9bf2ca4b2e5bf07dfbbd842e61ec

SF: Enforce thread safety of active mode access

Provide two RefreshRateConfigs APIs for retrieving the active mode:
getActiveMode for access from the main thread (which does not need
to lock nor copy), and getActiveModePtr for other threads.

Bug: 241285191
Test: Build (-Wthread-safety)
Change-Id: If156d85861ec2d82a394ba181314a6ba3048974f

services/surfaceflinger/Scheduler/Scheduler.cpp

diff --git a/services/surfaceflinger/Scheduler/Scheduler.cpp b/services/surfaceflinger/Scheduler/Scheduler.cpp
index 55ae013..bec39a7 100644
--- a/services/surfaceflinger/Scheduler/Scheduler.cpp
+++ b/services/surfaceflinger/Scheduler/Scheduler.cpp
@@ -182,7 +182,7 @@
 
 impl::EventThread::GetVsyncPeriodFunction Scheduler::makeGetVsyncPeriodFunction() const {
     return [this](uid_t uid) {
-        const Fps refreshRate = holdRefreshRateConfigs()->getActiveMode()->getFps();
+        const Fps refreshRate = holdRefreshRateConfigs()->getActiveModePtr()->getFps();
         const nsecs_t currentPeriod = mVsyncSchedule->period().ns() ?: refreshRate.getPeriodNsecs();
 
         const auto frameRate = getFrameRateOverride(uid);
@@ -320,7 +320,7 @@
     // mode change is in progress. In that case we shouldn't dispatch an event
     // as it will be dispatched when the current mode changes.
     if (std::scoped_lock lock(mRefreshRateConfigsLock);
-        mRefreshRateConfigs->getActiveMode() != mPolicy.mode) {
+        mRefreshRateConfigs->getActiveModePtr() != mPolicy.mode) {
         return;
     }
 
@@ -453,7 +453,7 @@
     if (now - last > kIgnoreDelay) {
         const auto refreshRate = [&] {
             std::scoped_lock lock(mRefreshRateConfigsLock);
-            return mRefreshRateConfigs->getActiveMode()->getFps();
+            return mRefreshRateConfigs->getActiveModePtr()->getFps();
         }();
         resyncToHardwareVsync(false, refreshRate);
     }
@@ -577,7 +577,7 @@
     // magic number
     const Fps refreshRate = [&] {
         std::scoped_lock lock(mRefreshRateConfigsLock);
-        return mRefreshRateConfigs->getActiveMode()->getFps();
+        return mRefreshRateConfigs->getActiveModePtr()->getFps();
     }();
 
     constexpr Fps FPS_THRESHOLD_FOR_KERNEL_TIMER = 65_Hz;