From 2e102a05ca24c15921795d3bc320ade8353319bb Mon Sep 17 00:00:00 2001 From: Mathias Agopian Date: Tue, 18 Jan 2011 15:51:30 -0800 Subject: [PATCH] fix [3361121] hang in glClear() - device unresponsive, OTA fails Generally we never want to lock a buffer for write access if it is at the "head" on the surfaceflinger side. The only exception (1) is when the buffer is not currently in use AND there is at least one queued buffer -- in which case, SurfaceFlinger will never use said buffer anymore, because on the next composition around, it will be able to retire the first queued buffer. The logic above relies on SurfaceFlinger always retiring and locking a buffer before composition -- unfortunately this didn't happen during a screenshot. This could leave us in a situation where a buffer is locked by the application for write, and used by SurfaceFlinger for texturing, causing a hang. Here, we fix this issue by never assuming the exception (1), it was intended as an optimization allowing ANativeWindow::lockBuffer() to return sooner and was justified when most of SF composition was done in software. The actual buffer locking is now ensured by gralloc. We could have handled screenshots in a similar way to a regular composition, but it could have caused glitches on screen, essentially, taking a screenshot could cause to skip a frame. Change-Id: I1f226b1ebdf6918439b687c2723955d55b842c55 --- libs/surfaceflinger_client/SharedBufferStack.cpp | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/libs/surfaceflinger_client/SharedBufferStack.cpp b/libs/surfaceflinger_client/SharedBufferStack.cpp index 3b2ef848b38f7..af11f97a0ca1f 100644 --- a/libs/surfaceflinger_client/SharedBufferStack.cpp +++ b/libs/surfaceflinger_client/SharedBufferStack.cpp @@ -261,8 +261,7 @@ bool SharedBufferClient::LockCondition::operator()() const { // NOTE: if stack.head is messed up, we could crash the client // or cause some drawing artifacts. This is okay, as long as it is // limited to the client. - return (buf != stack.index[stack.head] || - (stack.queued > 0 && stack.inUse != buf)); + return (buf != stack.index[stack.head]); } SharedBufferServer::BuffersAvailableCondition::BuffersAvailableCondition(