Commit 84f904ec authored by Alan Cox's avatar Alan Cox Committed by Greg Kroah-Hartman

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: default avatarClemens Ladisch <clemens@ladisch.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: default avatarAlan Cox <alan@linux.intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 69964ea4
...@@ -1085,15 +1085,21 @@ void vt_set_led_state(int console, int leds) ...@@ -1085,15 +1085,21 @@ void vt_set_led_state(int console, int leds)
* *
* Handle console start. This is a wrapper for the VT layer * Handle console start. This is a wrapper for the VT layer
* so that we can keep kbd knowledge internal * 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) void vt_kbd_con_start(int console)
{ {
struct kbd_struct * kbd = kbd_table + console; struct kbd_struct * kbd = kbd_table + console;
unsigned long flags; /* unsigned long flags; */
spin_lock_irqsave(&kbd_event_lock, flags); /* spin_lock_irqsave(&kbd_event_lock, flags); */
clr_vc_kbd_led(kbd, VC_SCROLLOCK); clr_vc_kbd_led(kbd, VC_SCROLLOCK);
set_leds(); 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) ...@@ -1102,22 +1108,28 @@ void vt_kbd_con_start(int console)
* *
* Handle console stop. This is a wrapper for the VT layer * Handle console stop. This is a wrapper for the VT layer
* so that we can keep kbd knowledge internal * 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) void vt_kbd_con_stop(int console)
{ {
struct kbd_struct * kbd = kbd_table + console; struct kbd_struct * kbd = kbd_table + console;
unsigned long flags; /* unsigned long flags; */
spin_lock_irqsave(&kbd_event_lock, flags); /* spin_lock_irqsave(&kbd_event_lock, flags); */
set_vc_kbd_led(kbd, VC_SCROLLOCK); set_vc_kbd_led(kbd, VC_SCROLLOCK);
set_leds(); 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 * This is the tasklet that updates LED state on all keyboards
* attached to the box. The reason we use tasklet is that we * attached to the box. The reason we use tasklet is that we
* need to handle the scenario when keyboard handler is not * 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. * update led state.
*/ */
static void kbd_bh(unsigned long dummy) static void kbd_bh(unsigned long dummy)
......
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