fix a possible deadlock when removing a layer and destroying a client
generally the last reference to a Layer is released in commitTransaction()
with mStateLock held. Layer itself only holds weak references to Client,
however, ~Layer() briefly promotes this weak reference -- during that time
the all other strong references to that Client go away, ~Layer is left with
the last one... then hell breaks loose as ~Client is called, which in turn
needs to acquire mStateLock.
We fix this by holding a temporary copy of the drawing state during
the transaction so that the side-effects of copying the current
state into the drawing state are seen only after mStateLock has
been released.
Bug: 9106453
Change-Id: Ic5348ac12283500ead87286a37565e8da35f1db2
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index ef0d521..e4d3c5f 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -1037,6 +1037,12 @@
{
ATRACE_CALL();
+ // here we keep a copy of the drawing state (that is the state that's
+ // going to be overwritten by handleTransactionLocked()) outside of
+ // mStateLock so that the side-effects of the State assignment
+ // don't happen with mStateLock held (which can cause deadlocks).
+ State drawingState(mDrawingState);
+
Mutex::Autolock _l(mStateLock);
const nsecs_t now = systemTime();
mDebugInTransaction = now;