Avoid a potential race condition on mDisplays

Update: The HWC1 path needed to be updated in light of a change to
SurfaceFlinger.h. The build now works for both paths.

Original Message:

The race could occur when transitioning in/out of VR flinger mode.
It is now avoided by ensuring that the primary |DisplayDevice| is always
created once |mStateLock| is released, and ensuring that all accesses
to the primary |DisplayDevice| are guarded by |mStateLock|.

Bug: 36194616
Bug: 37249613
Test: Compiled for both HWC1 and HWC2 surface flinger builds.
      Normal behavior is unchanged. Explicitly testing the race
      condition required instrumenting code with sleep statements.

Change-Id: I0b00e857a3b2fd01948a888db2f0715d2a8204c1

diff --git a/services/surfaceflinger/DisplayHardware/HWComposer.cpp b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
index 09434f6..32739b6 100644 (file)
--- a/services/surfaceflinger/DisplayHardware/HWComposer.cpp
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
@@ -206,7 +206,7 @@ void HWComposer::hotplug(const std::shared_ptr<HWC2::Display>& display,
         }
         disp = DisplayDevice::DISPLAY_EXTERNAL;
     }
-    mEventHandler->onHotplugReceived(disp,
+    mEventHandler->onHotplugReceived(this, disp,
             connected == HWC2::Connection::Connected);
 }
 

diff --git a/services/surfaceflinger/DisplayHardware/HWComposer.h b/services/surfaceflinger/DisplayHardware/HWComposer.h
index 81f1619..78d0307 100644 (file)
--- a/services/surfaceflinger/DisplayHardware/HWComposer.h
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.h
@@ -70,7 +70,7 @@ public:
         friend class HWComposer;
         virtual void onVSyncReceived(
             HWComposer* composer, int32_t disp, nsecs_t timestamp) = 0;
-        virtual void onHotplugReceived(int32_t disp, bool connected) = 0;
+        virtual void onHotplugReceived(HWComposer* composer, int32_t disp, bool connected) = 0;
         virtual void onInvalidateReceived(HWComposer* composer) = 0;
     protected:
         virtual ~EventHandler() {}

diff --git a/services/surfaceflinger/DisplayHardware/HWComposer_hwc1.cpp b/services/surfaceflinger/DisplayHardware/HWComposer_hwc1.cpp
index 5b5f1cf..dcb2913 100644 (file)
--- a/services/surfaceflinger/DisplayHardware/HWComposer_hwc1.cpp
+++ b/services/surfaceflinger/DisplayHardware/HWComposer_hwc1.cpp
@@ -315,7 +315,7 @@ void HWComposer::hotplug(int disp, int connected) {
     queryDisplayProperties(disp);
     // Do not teardown or recreate the primary display
     if (disp != HWC_DISPLAY_PRIMARY) {
-        mEventHandler.onHotplugReceived(disp, bool(connected));
+        mEventHandler.onHotplugReceived(this, disp, bool(connected));
     }
 }
 

diff --git a/services/surfaceflinger/DisplayHardware/HWComposer_hwc1.h b/services/surfaceflinger/DisplayHardware/HWComposer_hwc1.h
index f64d69a..4bc63bb 100644 (file)
--- a/services/surfaceflinger/DisplayHardware/HWComposer_hwc1.h
+++ b/services/surfaceflinger/DisplayHardware/HWComposer_hwc1.h
@@ -62,7 +62,7 @@ public:
         friend class HWComposer;
         virtual void onVSyncReceived(
             HWComposer* composer, int32_t disp, nsecs_t timestamp) = 0;
-        virtual void onHotplugReceived(int disp, bool connected) = 0;
+        virtual void onHotplugReceived(HWComposer* composer, int disp, bool connected) = 0;
         virtual void onInvalidateReceived(HWComposer* composer) = 0;
     protected:
         virtual ~EventHandler() {}

diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 26baaae..76a5d06 100644 (file)
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -598,7 +598,7 @@ void SurfaceFlinger::init() {
 
     // make the GLContext current so that we can create textures when creating
     // Layers (which may happens before we render something)
-    getDefaultDisplayDevice()->makeCurrent(mEGLDisplay, mEGLContext);
+    getDefaultDisplayDeviceLocked()->makeCurrent(mEGLDisplay, mEGLContext);
 
     mEventControlThread = new EventControlThread(this);
     mEventControlThread->run("EventControl", PRIORITY_URGENT_DISPLAY);
@@ -714,8 +714,11 @@ status_t SurfaceFlinger::getDisplayConfigs(const sp<IBinder>& display,
             info.density = density;
 
             // TODO: this needs to go away (currently needed only by webkit)
-            sp<const DisplayDevice> hw(getDefaultDisplayDevice());
-            info.orientation = hw->getOrientation();
+            {
+                Mutex::Autolock _l(mStateLock);
+                sp<const DisplayDevice> hw(getDefaultDisplayDeviceLocked());
+                info.orientation = hw->getOrientation();
+            }
         } else {
             // TODO: where should this value come from?
             static const int TV_DENSITY = 213;
@@ -772,10 +775,13 @@ int SurfaceFlinger::getActiveConfig(const sp<IBinder>& display) {
         ALOGE("%s : display is NULL", __func__);
         return BAD_VALUE;
     }
+
+    Mutex::Autolock _l(mStateLock);
     sp<DisplayDevice> device(getDisplayDevice(display));
     if (device != NULL) {
         return device->getActiveConfig();
     }
+
     return BAD_VALUE;
 }
 
@@ -863,6 +869,7 @@ status_t SurfaceFlinger::getDisplayColorModes(const sp<IBinder>& display,
 }
 
 android_color_mode_t SurfaceFlinger::getActiveColorMode(const sp<IBinder>& display) {
+    Mutex::Autolock _l(mStateLock);
     sp<DisplayDevice> device(getDisplayDevice(display));
     if (device != nullptr) {
         return device->getActiveColorMode();
@@ -1124,55 +1131,60 @@ void SurfaceFlinger::getCompositorTiming(CompositorTiming* compositorTiming) {
     *compositorTiming = mCompositorTiming;
 }
 
-void SurfaceFlinger::onHotplugReceived(int32_t disp, bool connected) {
-    ALOGV("onHotplugReceived(%d, %s)", disp, connected ? "true" : "false");
-    if (disp == DisplayDevice::DISPLAY_PRIMARY) {
-        Mutex::Autolock lock(mStateLock);
-
-        // All non-virtual displays are currently considered secure.
-        bool isSecure = true;
-
-        int32_t type = DisplayDevice::DISPLAY_PRIMARY;
+void SurfaceFlinger::createDefaultDisplayDevice() {
+    const int32_t type = DisplayDevice::DISPLAY_PRIMARY;
+    wp<IBinder> token = mBuiltinDisplays[type];
 
-        // When we're using the vr composer, the assumption is that we've
-        // already created the IBinder object for the primary display.
-        if (!mHwc->isUsingVrComposer()) {
-            createBuiltinDisplayLocked(DisplayDevice::DISPLAY_PRIMARY);
+    // All non-virtual displays are currently considered secure.
+    const bool isSecure = true;
+
+    sp<IGraphicBufferProducer> producer;
+    sp<IGraphicBufferConsumer> consumer;
+    BufferQueue::createBufferQueue(&producer, &consumer, new GraphicBufferAlloc());
+
+    sp<FramebufferSurface> fbs = new FramebufferSurface(*mHwc, type, consumer);
+
+    bool hasWideColorModes = false;
+    std::vector<android_color_mode_t> modes = getHwComposer().getColorModes(
+        type);
+    for (android_color_mode_t colorMode : modes) {
+        switch (colorMode) {
+            case HAL_COLOR_MODE_DISPLAY_P3:
+            case HAL_COLOR_MODE_ADOBE_RGB:
+            case HAL_COLOR_MODE_DCI_P3:
+                hasWideColorModes = true;
+                break;
+            default:
+                break;
         }
+    }
+    sp<DisplayDevice> hw = new DisplayDevice(this, DisplayDevice::DISPLAY_PRIMARY, type, isSecure,
+                                             token, fbs, producer, mRenderEngine->getEGLConfig(),
+                                             hasWideColorModes && hasWideColorDisplay);
+    mDisplays.add(token, hw);
+    android_color_mode defaultColorMode = HAL_COLOR_MODE_NATIVE;
+    if (hasWideColorModes && hasWideColorDisplay) {
+        defaultColorMode = HAL_COLOR_MODE_SRGB;
+    }
+    setActiveColorModeInternal(hw, defaultColorMode);
+}
 
-        wp<IBinder> token = mBuiltinDisplays[type];
+void SurfaceFlinger::onHotplugReceived(HWComposer* composer, int32_t disp, bool connected) {
+    ALOGV("onHotplugReceived(%d, %s)", disp, connected ? "true" : "false");
 
-        sp<IGraphicBufferProducer> producer;
-        sp<IGraphicBufferConsumer> consumer;
-        BufferQueue::createBufferQueue(&producer, &consumer,
-                new GraphicBufferAlloc());
-
-        sp<FramebufferSurface> fbs = new FramebufferSurface(*mHwc,
-                DisplayDevice::DISPLAY_PRIMARY, consumer);
-
-        bool hasWideColorModes = false;
-        std::vector<android_color_mode_t> modes = getHwComposer().getColorModes(type);
-        for (android_color_mode_t colorMode : modes) {
-            switch (colorMode) {
-                case HAL_COLOR_MODE_DISPLAY_P3:
-                case HAL_COLOR_MODE_ADOBE_RGB:
-                case HAL_COLOR_MODE_DCI_P3:
-                    hasWideColorModes = true;
-                    break;
-                default:
-                    break;
-            }
+    if (composer->isUsingVrComposer()) {
+        // We handle initializing the primary display device for the VR
+        // window manager hwc explicitly at the time of transition.
+        if (disp != DisplayDevice::DISPLAY_PRIMARY) {
+            ALOGE("External displays are not supported by the vr hardware composer.");
         }
-        sp<DisplayDevice> hw =
-                new DisplayDevice(this, DisplayDevice::DISPLAY_PRIMARY, disp, isSecure, token, fbs,
-                                  producer, mRenderEngine->getEGLConfig(),
-                                  hasWideColorModes && hasWideColorDisplay);
-        mDisplays.add(token, hw);
-        android_color_mode defaultColorMode = HAL_COLOR_MODE_NATIVE;
-        if (hasWideColorModes && hasWideColorDisplay) {
-            defaultColorMode = HAL_COLOR_MODE_SRGB;
-        }
-        setActiveColorModeInternal(hw, defaultColorMode);
+        return;
+    }
+
+    if (disp == DisplayDevice::DISPLAY_PRIMARY) {
+        Mutex::Autolock lock(mStateLock);
+        createBuiltinDisplayLocked(DisplayDevice::DISPLAY_PRIMARY);
+        createDefaultDisplayDevice();
     } else {
         auto type = DisplayDevice::DISPLAY_EXTERNAL;
         Mutex::Autolock _l(mStateLock);
@@ -1214,6 +1226,7 @@ void SurfaceFlinger::clearHwcLayers(const LayerVector& layers) {
     }
 }
 
+// Note: it is assumed the caller holds |mStateLock| when this is called
 void SurfaceFlinger::resetHwc() {
     disableHardwareVsync(true);
     clearHwcLayers(mDrawingState.layersSortedByZ);
@@ -1234,36 +1247,46 @@ void SurfaceFlinger::updateVrFlinger() {
     if (vrFlingerRequestsDisplay == mHwc->isUsingVrComposer()) {
         return;
     }
+
+    bool vrHwcNewlyInitialized = false;
+
     if (vrFlingerRequestsDisplay && !mVrHwc) {
         // Construct new HWComposer without holding any locks.
         mVrHwc = new HWComposer(true);
+        vrHwcNewlyInitialized = true;
         ALOGV("Vr HWC created");
     }
-    {
-        Mutex::Autolock _l(mStateLock);
 
-        if (vrFlingerRequestsDisplay) {
-            resetHwc();
+    Mutex::Autolock _l(mStateLock);
 
-            mHwc = mVrHwc;
-            mVrFlinger->GrantDisplayOwnership();
-        } else {
-            mVrFlinger->SeizeDisplayOwnership();
+    if (vrFlingerRequestsDisplay) {
+        resetHwc();
 
-            resetHwc();
+        mHwc = mVrHwc;
+        mVrFlinger->GrantDisplayOwnership();
 
-            mHwc = mRealHwc;
-            enableHardwareVsync();
+        if (vrHwcNewlyInitialized) {
+            mVrHwc->setEventHandler(
+                static_cast<HWComposer::EventHandler*>(this));
         }
+    } else {
+        mVrFlinger->SeizeDisplayOwnership();
 
-        mVisibleRegionsDirty = true;
-        invalidateHwcGeometry();
-        android_atomic_or(1, &mRepaintEverything);
-        setTransactionFlags(eDisplayTransactionNeeded);
-    }
-    if (mVrHwc) {
-        mVrHwc->setEventHandler(static_cast<HWComposer::EventHandler*>(this));
+        resetHwc();
+
+        mHwc = mRealHwc;
+        enableHardwareVsync();
     }
+
+    mVisibleRegionsDirty = true;
+    invalidateHwcGeometry();
+
+    // Explicitly re-initialize the primary display. This is because some other
+    // parts of this class rely on the primary display always being available.
+    createDefaultDisplayDevice();
+
+    android_atomic_or(1, &mRepaintEverything);
+    setTransactionFlags(eDisplayTransactionNeeded);
 }
 
 void SurfaceFlinger::onMessageReceived(int32_t what) {
@@ -1473,7 +1496,8 @@ void SurfaceFlinger::postComposition(nsecs_t refreshStartTime)
         layer->releasePendingBuffer(dequeueReadyTime);
     }
 
-    const sp<const DisplayDevice> hw(getDefaultDisplayDevice());
+    // |mStateLock| not needed as we are on the main thread
+    const sp<const DisplayDevice> hw(getDefaultDisplayDeviceLocked());
 
     std::shared_ptr<FenceTime> glCompositionDoneFenceTime;
     if (mHwc->hasClientComposition(HWC_DISPLAY_PRIMARY)) {
@@ -1821,7 +1845,8 @@ void SurfaceFlinger::postFramebuffer()
     mLastSwapBufferTime = systemTime() - now;
     mDebugInSwapBuffers = 0;
 
-    uint32_t flipCount = getDefaultDisplayDevice()->getPageFlipCount();
+    // |mStateLock| not needed as we are on the main thread
+    uint32_t flipCount = getDefaultDisplayDeviceLocked()->getPageFlipCount();
     if (flipCount % LOG_FRAME_STATS_PERIOD == 0) {
         logFrameStats();
     }
@@ -1906,7 +1931,7 @@ void SurfaceFlinger::handleTransactionLocked(uint32_t transactionFlags)
                         // Call makeCurrent() on the primary display so we can
                         // be sure that nothing associated with this display
                         // is current.
-                        const sp<const DisplayDevice> defaultDisplay(getDefaultDisplayDevice());
+                        const sp<const DisplayDevice> defaultDisplay(getDefaultDisplayDeviceLocked());
                         defaultDisplay->makeCurrent(mEGLDisplay, mEGLContext);
                         sp<DisplayDevice> hw(getDisplayDevice(draw.keyAt(i)));
                         if (hw != NULL)
@@ -2096,7 +2121,7 @@ void SurfaceFlinger::handleTransactionLocked(uint32_t transactionFlags)
                 // could be null when this layer is using a layerStack
                 // that is not visible on any display. Also can occur at
                 // screen off/on times.
-                disp = getDefaultDisplayDevice();
+                disp = getDefaultDisplayDeviceLocked();
             }
             layer->updateTransformHint(disp);
 
@@ -2452,7 +2477,9 @@ bool SurfaceFlinger::doComposeSurfaces(
             ALOGW("DisplayDevice::makeCurrent failed. Aborting surface composition for display %s",
                   displayDevice->getDisplayName().string());
             eglMakeCurrent(mEGLDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
-            if(!getDefaultDisplayDevice()->makeCurrent(mEGLDisplay, mEGLContext)) {
+
+            // |mStateLock| not needed as we are on the main thread
+            if(!getDefaultDisplayDeviceLocked()->makeCurrent(mEGLDisplay, mEGLContext)) {
               ALOGE("DisplayDevice::makeCurrent on default display failed. Aborting.");
             }
             return false;
@@ -3539,7 +3566,7 @@ void SurfaceFlinger::dumpAllLocked(const Vector<String16>& args, size_t& index,
     colorizer.reset(result);
 
     HWComposer& hwc(getHwComposer());
-    sp<const DisplayDevice> hw(getDefaultDisplayDevice());
+    sp<const DisplayDevice> hw(getDefaultDisplayDeviceLocked());
 
     colorizer.bold(result);
     result.appendFormat("EGL implementation : %s\n",
@@ -3769,7 +3796,7 @@ status_t SurfaceFlinger::onTransact(
                 return NO_ERROR;
             case 1013: {
                 Mutex::Autolock _l(mStateLock);
-                sp<const DisplayDevice> hw(getDefaultDisplayDevice());
+                sp<const DisplayDevice> hw(getDefaultDisplayDeviceLocked());
                 reply->writeInt32(hw->getPageFlipCount());
                 return NO_ERROR;
             }

diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 46121cf..219d662 100644 (file)
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -184,8 +184,9 @@ public:
     void repaintEverything();
 
     // returns the default Display
-    sp<const DisplayDevice> getDefaultDisplayDevice() const {
-        return getDisplayDevice(mBuiltinDisplays[DisplayDevice::DISPLAY_PRIMARY]);
+    sp<const DisplayDevice> getDefaultDisplayDevice() {
+        Mutex::Autolock _l(mStateLock);
+        return getDefaultDisplayDeviceLocked();
     }
 
     // utility function to delete a texture on the main thread
@@ -304,7 +305,7 @@ private:
      * HWComposer::EventHandler interface
      */
     virtual void onVSyncReceived(HWComposer* composer, int type, nsecs_t timestamp);
-    virtual void onHotplugReceived(int disp, bool connected);
+    virtual void onHotplugReceived(HWComposer* composer, int disp, bool connected);
     virtual void onInvalidateReceived(HWComposer* composer);
 
     /* ------------------------------------------------------------------------
@@ -439,6 +440,12 @@ private:
         return mDisplays.valueFor(dpy);
     }
 
+    sp<const DisplayDevice> getDefaultDisplayDeviceLocked() const {
+        return getDisplayDevice(mBuiltinDisplays[DisplayDevice::DISPLAY_PRIMARY]);
+    }
+
+    void createDefaultDisplayDevice();
+
     int32_t getDisplayType(const sp<IBinder>& display) {
         if (!display.get()) return NAME_NOT_FOUND;
         for (int i = 0; i < DisplayDevice::NUM_BUILTIN_DISPLAY_TYPES; ++i) {

diff --git a/services/surfaceflinger/SurfaceFlinger_hwc1.cpp b/services/surfaceflinger/SurfaceFlinger_hwc1.cpp
index e640ef7..cd2acef 100644 (file)
--- a/services/surfaceflinger/SurfaceFlinger_hwc1.cpp
+++ b/services/surfaceflinger/SurfaceFlinger_hwc1.cpp
@@ -584,7 +584,7 @@ void SurfaceFlinger::init() {
 
     // make the GLContext current so that we can create textures when creating Layers
     // (which may happens before we render something)
-    getDefaultDisplayDevice()->makeCurrent(mEGLDisplay, mEGLContext);
+    getDefaultDisplayDeviceLocked()->makeCurrent(mEGLDisplay, mEGLContext);
 
     mEventControlThread = new EventControlThread(this);
     mEventControlThread->run("EventControl", PRIORITY_URGENT_DISPLAY);
@@ -1040,7 +1040,7 @@ void SurfaceFlinger::getCompositorTiming(CompositorTiming* compositorTiming) {
     *compositorTiming = mCompositorTiming;
 }
 
-void SurfaceFlinger::onHotplugReceived(int type, bool connected) {
+void SurfaceFlinger::onHotplugReceived(HWComposer* /*composer*/, int type, bool connected) {
     if (mEventThread == NULL) {
         // This is a temporary workaround for b/7145521.  A non-null pointer
         // does not mean EventThread has finished initializing, so this
@@ -3222,7 +3222,7 @@ void SurfaceFlinger::dumpAllLocked(const Vector<String16>& args, size_t& index,
     colorizer.reset(result);
 
     HWComposer& hwc(getHwComposer());
-    sp<const DisplayDevice> hw(getDefaultDisplayDevice());
+    sp<const DisplayDevice> hw(getDefaultDisplayDeviceLocked());
 
     colorizer.bold(result);
     result.appendFormat("EGL implementation : %s\n",