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fix a possible deadlock when removing a layer and destroying a client

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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
This commit is contained in:
Mathias Agopian 2013-06-05 14:30:54 -07:00 committed by Jean-Baptiste Queru
parent 9f476fd080
commit e5886d9178
1 changed files with 6 additions and 0 deletions
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6
services/surfaceflinger/SurfaceFlinger.cpp
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@ -1037,6 +1037,12 @@ void SurfaceFlinger::handleTransaction(uint32_t transactionFlags)
{
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;