Re: [PATCH v2] Input: serport - defer write wakeups to a worker

[sashiko-bot@kernel.org]

> UART drivers can invoke the line discipline's write_wakeup() callback with
> their port lock held. serport forwards the notification directly to the
> serio driver. I-Force's callback can transmit a queued packet through
> serio_write(), which calls back into uart_write() and tries to acquire the
> same port lock. A notification after I-Force queues a packet but before it
> sets IFORCE_XMIT_RUNNING can therefore deadlock.
> 
> Defer the serio notification to a work item, as required for transmitting
> from a line discipline's write-wakeup path. Initialize the work disabled
> and enable it, along with TTY_DO_WRITE_WAKEUP, only when a serio driver
> with a write_wakeup() callback opens the port.
> 
> Clear TTY_DO_WRITE_WAKEUP and disable and drain the work when that driver
> closes the port, before the serio driver and port can be torn down. This
> allows the worker to call the driver without holding serport->lock,
> breaking the lock ordering cycle with input event callbacks that write
> to the UART.
> 
> Also clear TTY_DO_WRITE_WAKEUP and disable and drain the work on hangup,
> before waking the reader to unregister the serio port. The additional
> disable keeps the work disabled even if a driver opens the port while
> hangup is in progress.
> 
> Signed-off-by: James Hilliard <james.hilliard1@gmail.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261028-submit-serport-write-wakeup-v1-v2-1-c05d96259985@gmail.com?part=1