[PATCH] serial: 8250: drop lockdep annotation from serial8250_clear_IER()

Jiri Slaby (SUSE)
2023-08-11T06:43:49Z

The port lock is not always held when calling serial8250_clear_IER().
When an oops is in progress, the lock is tried to be taken and when it
is not, a warning is issued:
WARNING: CPU: 0 PID: 1 at drivers/tty/serial/8250/8250_port.c:707 +0x57/0x60
Modules linked in:
CPU: 0 PID: 1 Comm: init Not tainted 6.5.0-rc5-1.g225bfb7-default+ #774 00f1be860db663ed29479b8255d3b01ab1135bd3
Hardware name: QEMU Standard PC ...
RIP: 0010:serial8250_clear_IER+0x57/0x60
...
Call Trace:
<TASK>
serial8250_console_write+0x9e/0x4b0
console_flush_all+0x217/0x5f0
...

Therefore, remove the annotation as it doesn't hold for all invocations.

The other option would be to make the lockdep test conditional on
'oops_in_progress' or pass 'locked' from serial8250_console_write(). I
don't think, that is worth it.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Cc: John Ogness <john.ogness@linutronix.de>
Fixes: d0b309a5d3f4 (serial: 8250: synchronize and annotate UART_IER access)
---
drivers/tty/serial/8250/8250_port.c | 3 ---
1 file changed, 3 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index ecfdc4534123..f59328e1c35d 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -703,9 +703,6 @@ static void serial8250_set_sleep(struct uart_8250_port *p, int sleep)

static void serial8250_clear_IER(struct uart_8250_port *up)
{
- /* Port locked to synchronize UART_IER access against the console. */
- lockdep_assert_held_once(&up->port.lock);
-
if (up->capabilities & UART_CAP_UUE)
serial_out(up, UART_IER, UART_IER_UUE);
else
--
2.41.0