Commit 5f1149d2 authored by Jiri Slaby (SUSE)'s avatar Jiri Slaby (SUSE) Committed by Greg Kroah-Hartman
Browse files

serial: drop debugging WARN_ON_ONCE() from uart_put_char() 



Pengfei Xu reports, that the -next commit 1788cf6a (tty: serial:
switch from circ_buf to kfifo) tries to emit a WARNING and that leads to
lockdep errors. Obviously we cannot print anything from uart_put_char()!

This WARN_ON_ONCE() was/is a debug aid to check if the condition in
uart_put_char() can happen at all. Pengfei Xu confirmed it can. Unlike
me and kbuild bot in my queue.

Second, I completely forgot about it, so I did not remove it in the
final version, nor mentioned it in the commit log.

Drop it now as we are all good. And we even have stack traces (and a
reproducer)!

Signed-off-by: default avatarJiri Slaby (SUSE) <jirislaby@kernel.org>
Reported-by: default avatarPengfei Xu <pengfei.xu@intel.com>
Link: https://lore.kernel.org/r/20240416071904.21440-1-jirislaby@kernel.org


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 35fad98e

drivers/tty/serial/serial_core.c

+1 −1
Original line number Diff line number Diff line
@@ -558,7 +558,7 @@ static int uart_put_char(struct tty_struct *tty, u8 c) 
	int ret = 0;



	port = uart_port_lock(state, flags);

	if (WARN_ON_ONCE(!state->port.xmit_buf)) {

	if (!state->port.xmit_buf) {

		uart_port_unlock(port, flags);

		return 0;

	}