Re: [PATCH v2] tty: discard flip-buffer input for TCSAFLUSH

[sashiko-bot@kernel.org]

> set_termios() handles TERMIOS_FLUSH by clearing only the line discipline's
> input buffer. Data already committed to the tty flip buffers can be
> delivered after that flush, leaving old input readable after a successful
> tcsetattr(TCSAFLUSH).
> 
> This can be reproduced with a noncanonical PTY: complete an 8192-byte
> master write, wait until the slave reports 4095 unread bytes, and apply
> TCSAFLUSH. The remaining 4097 bytes are still readable afterwards. Small
> amounts of pending input can also survive if they have not reached the
> line discipline yet.
> 
> Use tty_buffer_flush() with the referenced line discipline to discard both
> receive queues under the existing buffer lock. If the line discipline has
> a flush_buffer callback, also unthrottle the tty after releasing that lock,
> as TCIFLUSH does. Otherwise a paused input source or sleeping PTY writer
> can remain stopped after the queues are emptied.
> 
> Signed-off-by: Hungyu Lin <dennylin0707@gmail.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261027082236.56724-1-dennylin0707@gmail.com?part=1