Camera2: Fix potential deadlock

setPreviewWindow was holding a lock during long-lasting HAL calls
which may cause deadlock if the HAL calls back into the service during
the call. Stop holding the lock during these calls, since it's not
essential to do so.

Bug: 7320517
Change-Id: I4a35703d751e22ac32979b5a1288e291610576e7

1 files changed, 11 insertions, 7 deletions

diff --git a/services/camera/libcameraservice/Camera2Client.cpp b/services/camera/libcameraservice/Camera2Client.cpp
index 98332f90..06754005 100644
--- a/services/camera/libcameraservice/Camera2Client.cpp
+++ b/services/camera/libcameraservice/Camera2Client.cpp
@@ -529,15 +529,19 @@ status_t Camera2Client::setPreviewWindowL(const sp<IBinder>& binder,
         return NO_ERROR;
     }
 
-    SharedParameters::Lock l(mParameters);
-    switch (l.mParameters.state) {
+    Parameters::State state;
+    {
+        SharedParameters::Lock l(mParameters);
+        state = l.mParameters.state;
+    }
+    switch (state) {
         case Parameters::DISCONNECTED:
         case Parameters::RECORD:
         case Parameters::STILL_CAPTURE:
         case Parameters::VIDEO_SNAPSHOT:
             ALOGE("%s: Camera %d: Cannot set preview display while in state %s",
                     __FUNCTION__, mCameraId,
-                    Parameters::getStateName(l.mParameters.state));
+                    Parameters::getStateName(state));
             return INVALID_OPERATION;
         case Parameters::STOPPED:
         case Parameters::WAITING_FOR_PREVIEW_WINDOW:
@@ -545,10 +549,8 @@ status_t Camera2Client::setPreviewWindowL(const sp<IBinder>& binder,
             break;
         case Parameters::PREVIEW:
             // Already running preview - need to stop and create a new stream
-            // TODO: Optimize this so that we don't wait for old stream to drain
-            // before spinning up new stream
             mStreamingProcessor->stopStream();
-            l.mParameters.state = Parameters::WAITING_FOR_PREVIEW_WINDOW;
+            state = Parameters::WAITING_FOR_PREVIEW_WINDOW;
             break;
     }
 
@@ -560,7 +562,9 @@ status_t Camera2Client::setPreviewWindowL(const sp<IBinder>& binder,
         return res;
     }
 
-    if (l.mParameters.state == Parameters::WAITING_FOR_PREVIEW_WINDOW) {
+    if (state == Parameters::WAITING_FOR_PREVIEW_WINDOW) {
+        SharedParameters::Lock l(mParameters);
+        l.mParameters.state = state;
         return startPreviewL(l.mParameters, false);
     }