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Commit c7d56010 authored by Mathias Agopian's avatar Mathias Agopian
Browse files

make sure to update the tail pointer when undoing a dequeue

parent 46cd3afb

include/private/ui/SharedBufferStack.h

+2 −0
Original line number Original line Diff line number Diff line
@@ -229,6 +229,8 @@ private: 
    friend struct DequeueCondition;

    friend struct DequeueCondition;

    friend struct LockCondition;

    friend struct LockCondition;

    

    

    int32_t computeTail() const;



    struct QueueUpdate : public UpdateBase {

    struct QueueUpdate : public UpdateBase {

        inline QueueUpdate(SharedBufferBase* sbb);

        inline QueueUpdate(SharedBufferBase* sbb);

        inline ssize_t operator()();

        inline ssize_t operator()();

libs/ui/SharedBufferStack.cpp

+15 −5
Original line number Original line Diff line number Diff line
@@ -245,20 +245,27 @@ ssize_t SharedBufferServer::StatusUpdate::operator()() { 
SharedBufferClient::SharedBufferClient(SharedClient* sharedClient,

SharedBufferClient::SharedBufferClient(SharedClient* sharedClient,

        int surface, int num)

        int surface, int num)

    : SharedBufferBase(sharedClient, surface, num), tail(0)

    : SharedBufferBase(sharedClient, surface, num), tail(0)

{

    tail = computeTail();

}



int32_t SharedBufferClient::computeTail() const

{

{

    SharedBufferStack& stack( *mSharedStack );

    SharedBufferStack& stack( *mSharedStack );

    int32_t avail;

    int32_t head;

    // we need to make sure we read available and head coherently,

    // we need to make sure we read available and head coherently,

    // w.r.t RetireUpdate.

    // w.r.t RetireUpdate.

    int32_t newTail;

    int32_t avail;

    int32_t head;

    do {

    do {

        avail = stack.available;

        avail = stack.available;

        head = stack.head;

        head = stack.head;

    } while (stack.available != avail);

    } while (stack.available != avail);

    tail = head - avail + 1;

    newTail = head - avail + 1;

    if (tail < 0) {

    if (newTail < 0) {

        tail += num;

        newTail += mNumBuffers;

    }

    }

    return newTail;

}

}





ssize_t SharedBufferClient::dequeue()

ssize_t SharedBufferClient::dequeue()
@@ -296,6 +303,9 @@ status_t SharedBufferClient::undoDequeue(int buf) 
{

{

    UndoDequeueUpdate update(this);

    UndoDequeueUpdate update(this);

    status_t err = updateCondition( update );

    status_t err = updateCondition( update );

    if (err == NO_ERROR) {

        tail = computeTail();

    }

    return err;

    return err;

}

}