From 84f904ecd3aa2ccb5779b815b69c1cb592f07bb5 Mon Sep 17 00:00:00 2001 From: Alan Cox Date: Tue, 1 May 2012 16:12:19 +0100 Subject: [PATCH] vt: Fix deadlock on scroll-lock Fixing the locking accidentally replaced a race in the scroll lock handling with a deadlock. Turn it back into a race for now. The basic problem is that there are two paths into the tty stop/start helpers. One via the tty layer ^S/^Q handling where we need to take the kbd_event_lock and one via the special keyboard handler for fn_hold where we already hold it. Probably we need to split out into a separate LED lock but for now just go back to the race as it's a bit close to release. Reported-by: Clemens Ladisch Cc: Jiri Kosina Signed-off-by: Alan Cox Signed-off-by: Greg Kroah-Hartman --- drivers/tty/vt/keyboard.c | 26 +++++++++++++++++++------- 1 file changed, 19 insertions(+), 7 deletions(-) diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c index 86dd1e302bb3..29ca20dbd335 100644 --- a/drivers/tty/vt/keyboard.c +++ b/drivers/tty/vt/keyboard.c @@ -1085,15 +1085,21 @@ void vt_set_led_state(int console, int leds) * * Handle console start. This is a wrapper for the VT layer * so that we can keep kbd knowledge internal + * + * FIXME: We eventually need to hold the kbd lock here to protect + * the LED updating. We can't do it yet because fn_hold calls stop_tty + * and start_tty under the kbd_event_lock, while normal tty paths + * don't hold the lock. We probably need to split out an LED lock + * but not during an -rc release! */ void vt_kbd_con_start(int console) { struct kbd_struct * kbd = kbd_table + console; - unsigned long flags; - spin_lock_irqsave(&kbd_event_lock, flags); +/* unsigned long flags; */ +/* spin_lock_irqsave(&kbd_event_lock, flags); */ clr_vc_kbd_led(kbd, VC_SCROLLOCK); set_leds(); - spin_unlock_irqrestore(&kbd_event_lock, flags); +/* spin_unlock_irqrestore(&kbd_event_lock, flags); */ } /** @@ -1102,22 +1108,28 @@ void vt_kbd_con_start(int console) * * Handle console stop. This is a wrapper for the VT layer * so that we can keep kbd knowledge internal + * + * FIXME: We eventually need to hold the kbd lock here to protect + * the LED updating. We can't do it yet because fn_hold calls stop_tty + * and start_tty under the kbd_event_lock, while normal tty paths + * don't hold the lock. We probably need to split out an LED lock + * but not during an -rc release! */ void vt_kbd_con_stop(int console) { struct kbd_struct * kbd = kbd_table + console; - unsigned long flags; - spin_lock_irqsave(&kbd_event_lock, flags); +/* unsigned long flags; */ +/* spin_lock_irqsave(&kbd_event_lock, flags); */ set_vc_kbd_led(kbd, VC_SCROLLOCK); set_leds(); - spin_unlock_irqrestore(&kbd_event_lock, flags); +/* spin_unlock_irqrestore(&kbd_event_lock, flags); */ } /* * This is the tasklet that updates LED state on all keyboards * attached to the box. The reason we use tasklet is that we * need to handle the scenario when keyboard handler is not - * registered yet but we already getting updates form VT to + * registered yet but we already getting updates from the VT to * update led state. */ static void kbd_bh(unsigned long dummy) -- 2.20.1