sf: Fix incorrect state reporting in dumpsys

Dumpsys utility access layer compositionType variable
with out proper protection. These variables are modified
during hwc_prepare call. Existing HAL lock protection is not
sufficient to address this issue. Failure to do this will
result in incorrect state reporting in dumpsys.

A new drawLock mutex in HWComposer that will be used in both
dumpsys and draw calls to ensure correct state is accessed.

Change-Id: I6289e0a3d1f5bbf35a18ddcd0538c9cda3e96c27

2 files changed, 4 insertions, 0 deletions

diff --git a/services/surfaceflinger/DisplayHardware/HWComposer.cpp b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
index f123e6dd0..bc67dfda7 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.cpp
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
@@ -733,6 +733,7 @@ status_t HWComposer::setFramebufferTarget(int32_t id,
 }
 
 status_t HWComposer::prepare() {
+    Mutex::Autolock _l(mDrawLock);
     for (size_t i=0 ; i<mNumDisplays ; i++) {
         DisplayData& disp(mDisplayData[i]);
         if (disp.framebufferTarget) {
@@ -1375,6 +1376,7 @@ HWComposer::LayerListIterator HWComposer::end(int32_t id) {
 }
 
 void HWComposer::dump(String8& result) const {
+    Mutex::Autolock _l(mDrawLock);
     if (mHwc) {
         result.appendFormat("Hardware Composer state (version %8x):\n", hwcApiVersion(mHwc));
         result.appendFormat("  mDebugForceFakeVSync=%d\n", mDebugForceFakeVSync);
diff --git a/services/surfaceflinger/DisplayHardware/HWComposer.h b/services/surfaceflinger/DisplayHardware/HWComposer.h
index 1969349d8..c8d2b57e6 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.h
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.h
@@ -369,6 +369,8 @@ private:
 
     // protected by mLock
     mutable Mutex mLock;
+    // synchronization between Draw call and Dumpsys call
+    mutable Mutex mDrawLock;
     mutable nsecs_t mLastHwVSync[HWC_NUM_PHYSICAL_DISPLAY_TYPES];
 
     // thread-safe