fix [2873058] Surface::dequeueBuffer blocks on last buffer, i.e. cannot dequeue all allocated buffers at once.

this situation happened when the last buffer needed to be resized
(or allocated, the first time). the assumption was that the buffer
was in use by SF itself as the current buffer (obviously, this
assumption made no sense when the buffer had never been allocated, btw).

the system would wait until some other buffer became the "front" buffer.

we fix this problem by entirely removing the requirement that the
buffer being resized cannot be the front buffer. instead, we just
allocate a new buffer and replace the front buffer by the new one.

the downside is that this uses more memory (an extra buffer) for a
brief amount of time while the old buffer is being reallocated and
before it has actually been replaced.

Change-Id: I022e4621209474ceb1c671b23deb4188eaaa7285

1 files changed, 0 insertions, 30 deletions

diff --git a/libs/surfaceflinger_client/SharedBufferStack.cpp b/libs/surfaceflinger_client/SharedBufferStack.cpp
index d67a589..156a7db 100644
--- a/libs/surfaceflinger_client/SharedBufferStack.cpp
+++ b/libs/surfaceflinger_client/SharedBufferStack.cpp
@@ -243,21 +243,6 @@ bool SharedBufferClient::LockCondition::operator()() const {
             (stack.queued > 0 && stack.inUse != buf));
 }
 
-SharedBufferServer::ReallocateCondition::ReallocateCondition(
-        SharedBufferBase* sbb, int buf) : ConditionBase(sbb), buf(buf) { 
-}
-bool SharedBufferServer::ReallocateCondition::operator()() const {
-    int32_t head = stack.head;
-    if (uint32_t(head) >= SharedBufferStack::NUM_BUFFER_MAX) {
-        // if stack.head is messed up, we cannot allow the server to
-        // crash (since stack.head is mapped on the client side)
-        stack.status = BAD_VALUE;
-        return false;
-    }
-    // TODO: we should also check that buf has been dequeued
-    return (buf != stack.index[head]);
-}
-
 // ----------------------------------------------------------------------------
 
 SharedBufferClient::QueueUpdate::QueueUpdate(SharedBufferBase* sbb)
@@ -558,21 +543,6 @@ int32_t SharedBufferServer::getQueuedCount() const
     return stack.queued;
 }
 
-status_t SharedBufferServer::assertReallocate(int buf)
-{
-    /*
-     * NOTE: it's safe to hold mLock for read while waiting for
-     * the ReallocateCondition because that condition is not updated
-     * by the thread that holds mLock for write.
-     */
-    RWLock::AutoRLock _l(mLock);
-
-    // TODO: need to validate "buf"
-    ReallocateCondition condition(this, buf);
-    status_t err = waitForCondition(condition);
-    return err;
-}
-
 Region SharedBufferServer::getDirtyRegion(int buf) const
 {
     SharedBufferStack& stack( *mSharedStack );