pmz_interrupt() drains both channels but, since commit 2e124b4a390c ("TTY: switch tty_flip_buffer_push"), pushes the flip buffer of the port whose handler is running rather than the port that was drained. With both ports open, data received on the other port can be left in its flip buffer until something else pushes it, so its reader may not see it. Fixes: 2e124b4a390c ("TTY: switch tty_flip_buffer_push") Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Tim Douglas <me@timdoug.com> Link: https://patch.msgid.link/20261013013541.4535-2-me@timdoug.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>