Re: [PATCH v4 4/4] serial: 8250: retire canceled RX DMA before reusing the receive buffer

[sashiko-bot@kernel.org]

> The RX timeout path pauses a transfer, copies its data and terminates it
> asynchronously. Clearing rx_running at that point lets another receive
> reuse the buffer and cookie while the old callback is still waiting for
> the port lock. Inspecting the new cookie cannot distinguish that callback
> from the completion of a new transfer.
> 
> Reserve the receive buffer until a worker has drained the canceled
> callbacks. Keep FIFO access separate from callback retirement: after a
> successful pause and termination, clear rx_running while rx_terminating
> prevents another descriptor from reusing the buffer. Deliver the paused
> data before allowing the interrupt handler to drain the FIFO through PIO.
> Normal retirement only releases ownership and leaves subsequent receive
> handling to the UART interrupt.
> 
> Preserve the normal completion-path LSR read and gate DMA resubmission on
> [ ... ]
> provider still cannot terminate the channel in process context, retain
> its buffer and leave receive interrupts masked.
> 
> Fixes: 9ee4b83e51f7 ("serial: 8250: Add support for dmaengine")
> Signed-off-by: James Hilliard <james.hilliard1@gmail.com>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261023-submit-serial-8250-dma-cancel-v1-v4-0-e759de1839de@gmail.com?part=4