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Merge change 24947 into eclair

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* changes:
  make sure to update the tail pointer when undoing a dequeue
This commit is contained in:
Android (Google) Code Review 2009-09-14 19:01:40 -04:00
commit ab0fb1be89
2 changed files with 17 additions and 5 deletions
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2
include/private/ui/SharedBufferStack.h
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@ -228,6 +228,8 @@ private:
friend struct Condition;
friend struct DequeueCondition;
friend struct LockCondition;
int32_t computeTail() const;
struct QueueUpdate : public UpdateBase {
inline QueueUpdate(SharedBufferBase* sbb);

20
libs/ui/SharedBufferStack.cpp
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@ -245,20 +245,27 @@ ssize_t SharedBufferServer::StatusUpdate::operator()() {
SharedBufferClient::SharedBufferClient(SharedClient* sharedClient,
int surface, int num)
: SharedBufferBase(sharedClient, surface, num), tail(0)
{
tail = computeTail();
}
int32_t SharedBufferClient::computeTail() const
{
SharedBufferStack& stack( *mSharedStack );
int32_t avail;
int32_t head;
// we need to make sure we read available and head coherently,
// w.r.t RetireUpdate.
int32_t newTail;
int32_t avail;
int32_t head;
do {
avail = stack.available;
head = stack.head;
} while (stack.available != avail);
tail = head - avail + 1;
if (tail < 0) {
tail += num;
newTail = head - avail + 1;
if (newTail < 0) {
newTail += mNumBuffers;
}
return newTail;
}
ssize_t SharedBufferClient::dequeue()
@ -296,6 +303,9 @@ status_t SharedBufferClient::undoDequeue(int buf)
{
UndoDequeueUpdate update(this);
status_t err = updateCondition( update );
if (err == NO_ERROR) {
tail = computeTail();
}
return err;
}