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/RefreshRateConfigs.h

diff --git a/services/surfaceflinger/Scheduler/RefreshRateConfigs.h b/services/surfaceflinger/Scheduler/RefreshRateConfigs.h
index a79002e..b2cfb03 100644
--- a/services/surfaceflinger/Scheduler/RefreshRateConfigs.h
+++ b/services/surfaceflinger/Scheduler/RefreshRateConfigs.h
@@ -31,6 +31,7 @@
 #include "DisplayHardware/HWComposer.h"
 #include "Scheduler/OneShotTimer.h"
 #include "Scheduler/StrongTyping.h"
+#include "ThreadContext.h"
 
 namespace android::scheduler {
 
@@ -207,8 +208,11 @@
     // uses the primary range, not the app request range.
     DisplayModePtr getMaxRefreshRateByPolicy() const EXCLUDES(mLock);
 
-    void setActiveModeId(DisplayModeId) EXCLUDES(mLock);
-    DisplayModePtr getActiveMode() const EXCLUDES(mLock);
+    void setActiveModeId(DisplayModeId) EXCLUDES(mLock) REQUIRES(kMainThreadContext);
+
+    // See mActiveModeIt for thread safety.
+    DisplayModePtr getActiveModePtr() const EXCLUDES(mLock);
+    const DisplayMode& getActiveMode() const REQUIRES(kMainThreadContext);
 
     // Returns a known frame rate that is the closest to frameRate
     Fps findClosestKnownFrameRate(Fps frameRate) const;
@@ -332,6 +336,9 @@
 
     void constructAvailableRefreshRates() REQUIRES(mLock);
 
+    // See mActiveModeIt for thread safety.
+    DisplayModeIterator getActiveModeItLocked() const REQUIRES(mLock);
+
     std::pair<DisplayModePtr, GlobalSignals> getBestRefreshRateLocked(
             const std::vector<LayerRequirement>&, GlobalSignals) const REQUIRES(mLock);
 
@@ -345,10 +352,8 @@
 
     // Returns the highest refresh rate according to the current policy. May change at runtime. Only
     // uses the primary range, not the app request range.
+    const DisplayModePtr& getMaxRefreshRateByPolicyLocked() const REQUIRES(mLock);
     const DisplayModePtr& getMaxRefreshRateByPolicyLocked(int anchorGroup) const REQUIRES(mLock);
-    const DisplayModePtr& getMaxRefreshRateByPolicyLocked() const REQUIRES(mLock) {
-        return getMaxRefreshRateByPolicyLocked(mActiveModeIt->second->getGroup());
-    }
 
     const Policy* getCurrentPolicyLocked() const REQUIRES(mLock);
     bool isPolicyValidLocked(const Policy& policy) const REQUIRES(mLock);
@@ -361,7 +366,8 @@
     float calculateNonExactMatchingLayerScoreLocked(const LayerRequirement&, Fps refreshRate) const
             REQUIRES(mLock);
 
-    void updateDisplayModes(DisplayModes, DisplayModeId activeModeId) EXCLUDES(mLock);
+    void updateDisplayModes(DisplayModes, DisplayModeId activeModeId) EXCLUDES(mLock)
+            REQUIRES(kMainThreadContext);
 
     void initializeIdleTimer();
 
@@ -377,7 +383,10 @@
     // is also dependent, so must be reset as well.
     DisplayModes mDisplayModes GUARDED_BY(mLock);
 
-    DisplayModeIterator mActiveModeIt GUARDED_BY(mLock);
+    // Written under mLock exclusively from kMainThreadContext, so reads from kMainThreadContext
+    // need not be under mLock.
+    DisplayModeIterator mActiveModeIt GUARDED_BY(mLock) GUARDED_BY(kMainThreadContext);
+
     DisplayModeIterator mMinRefreshRateModeIt GUARDED_BY(mLock);
     DisplayModeIterator mMaxRefreshRateModeIt GUARDED_BY(mLock);