Fix potential deadlock in stopPreview/stopRecord.
Some camera HALs spin up a preview thread and need to wait for
the thread to exit. This can create a potential deadlock. In
stopPreview, we take the main lock. If a preview callback occurs
while the lock is held, the preview thread will block. If the
camera HAL is waiting for the preview thread to exit, this will
cause a deadlock.
This patch breaks out the preview buffer heap into a separate
mutex. This mutex is never held when the main lock is held, thus
preventing the deadlock from occuring.
diff --git a/camera/libcameraservice/CameraService.cpp b/camera/libcameraservice/CameraService.cpp
index e548524..df59dcf 100644
--- a/camera/libcameraservice/CameraService.cpp
+++ b/camera/libcameraservice/CameraService.cpp
@@ -683,22 +683,30 @@
{
LOGD("stopPreview (pid %d)", getCallingPid());
- Mutex::Autolock lock(mLock);
- if (checkPid() != NO_ERROR) return;
+ // hold main lock during state transition
+ {
+ Mutex::Autolock lock(mLock);
+ if (checkPid() != NO_ERROR) return;
- if (mHardware == 0) {
- LOGE("mHardware is NULL, returning.");
- return;
+ if (mHardware == 0) {
+ LOGE("mHardware is NULL, returning.");
+ return;
+ }
+
+ mHardware->stopPreview();
+ mHardware->disableMsgType(CAMERA_MSG_PREVIEW_FRAME);
+ LOGD("stopPreview(), hardware stopped OK");
+
+ if (mSurface != 0 && !mUseOverlay) {
+ mSurface->unregisterBuffers();
+ }
}
- mHardware->stopPreview();
- mHardware->disableMsgType(CAMERA_MSG_PREVIEW_FRAME);
- LOGD("stopPreview(), hardware stopped OK");
-
- if (mSurface != 0 && !mUseOverlay) {
- mSurface->unregisterBuffers();
+ // hold preview buffer lock
+ {
+ Mutex::Autolock lock(mPreviewLock);
+ mPreviewBuffer.clear();
}
- mPreviewBuffer.clear();
}
// stop recording mode
@@ -706,24 +714,31 @@
{
LOGD("stopRecording (pid %d)", getCallingPid());
- Mutex::Autolock lock(mLock);
- if (checkPid() != NO_ERROR) return;
+ // hold main lock during state transition
+ {
+ Mutex::Autolock lock(mLock);
+ if (checkPid() != NO_ERROR) return;
- if (mHardware == 0) {
- LOGE("mHardware is NULL, returning.");
- return;
+ if (mHardware == 0) {
+ LOGE("mHardware is NULL, returning.");
+ return;
+ }
+
+ if (mMediaPlayerBeep.get() != NULL) {
+ mMediaPlayerBeep->seekTo(0);
+ mMediaPlayerBeep->start();
+ }
+
+ mHardware->stopRecording();
+ mHardware->disableMsgType(CAMERA_MSG_VIDEO_FRAME);
+ LOGD("stopRecording(), hardware stopped OK");
}
- if (mMediaPlayerBeep.get() != NULL) {
- mMediaPlayerBeep->seekTo(0);
- mMediaPlayerBeep->start();
+ // hold preview buffer lock
+ {
+ Mutex::Autolock lock(mPreviewLock);
+ mPreviewBuffer.clear();
}
-
- mHardware->stopRecording();
- mHardware->disableMsgType(CAMERA_MSG_VIDEO_FRAME);
- LOGD("stopRecording(), hardware stopped OK");
-
- mPreviewBuffer.clear();
}
// release a recording frame
@@ -1216,10 +1231,10 @@
// provided it's big enough. Don't allocate the memory or
// perform the copy if there's no callback.
- // hold the lock while we grab a reference to the preview buffer
+ // hold the preview lock while we grab a reference to the preview buffer
sp<MemoryHeapBase> previewBuffer;
{
- Mutex::Autolock lock(mLock);
+ Mutex::Autolock lock(mPreviewLock);
if (mPreviewBuffer == 0) {
mPreviewBuffer = new MemoryHeapBase(size, 0, NULL);
} else if (size > mPreviewBuffer->virtualSize()) {
diff --git a/camera/libcameraservice/CameraService.h b/camera/libcameraservice/CameraService.h
index 41c5d99..3e3e54f 100644
--- a/camera/libcameraservice/CameraService.h
+++ b/camera/libcameraservice/CameraService.h
@@ -181,7 +181,6 @@
mutable Condition mReady;
sp<CameraService> mCameraService;
sp<ISurface> mSurface;
- sp<MemoryHeapBase> mPreviewBuffer;
int mPreviewCallbackFlag;
sp<MediaPlayer> mMediaPlayerClick;
@@ -197,6 +196,9 @@
sp<OverlayRef> mOverlayRef;
int mOverlayW;
int mOverlayH;
+
+ mutable Mutex mPreviewLock;
+ sp<MemoryHeapBase> mPreviewBuffer;
};
// ----------------------------------------------------------------------------