serial: 8250_core: use guard() in serial_unlink_irq_chain()

Having all the new guards, use them in the 8250 code. This improves
readability, makes error handling easier, and marks locked portions of
code explicit.

serial_unlink_irq_chain() is done separately here because with the
guard() used, those BUG_ON()s can be switched WARN_ON()s as we can
actually handle the conditions and return (despite something went really
wrong).

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20250814072456.182853-11-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index 82c3636451e5f9761f13b15b5e842d3e84298eeb..7d931693b311dc46ed4662f5afa8c5edb454a660 100644 (file)
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -178,20 +178,22 @@ static void serial_unlink_irq_chain(struct uart_8250_port *up)
 {
        struct irq_info *i;
 
-       mutex_lock(&hash_mutex);
+       guard(mutex)(&hash_mutex);
 
        hash_for_each_possible(irq_lists, i, node, up->port.irq)
-               if (i->irq == up->port.irq)
-                       break;
+               if (i->irq == up->port.irq) {
+                       if (WARN_ON(i->head == NULL))
+                               return;
 
-       BUG_ON(i == NULL);
-       BUG_ON(i->head == NULL);
+                       if (list_empty(i->head))
+                               free_irq(up->port.irq, i);
 
-       if (list_empty(i->head))
-               free_irq(up->port.irq, i);
+                       serial_do_unlink(i, up);
+
+                       return;
+               }
 
-       serial_do_unlink(i, up);
-       mutex_unlock(&hash_mutex);
+       WARN_ON(1);
 }
 
 /*