Qt wayland may freeze with no available buffer in QWaylandShmBackingStore if window show/hide very fast

main.cpp

Here's a simple program to reproduce the issue.

It creates two QRasterWindow , the latter one will be resized with show and hide on a QTimer (1ms). The resize is necessary to invalidate the buffer in the backing store.

The program will almost immediately freeze at this line

https://github.com/qt/qtwayland/blob/6.6.0/src/client/qwaylandshmbackingstore.cpp#L280

and it won't recover from the freeze with some log

qt.qpa.wayland.backingstore: QWaylandShmBackingStore: stalling waiting for a buffer to be released from the compositor...