Messages in this thread | | | Date | Fri, 27 Sep 2013 10:15:48 +0300 | From | Tomi Valkeinen <> | Subject | Re: [PATCH] fbcon: fix deadlock in fbcon_generic_blank() |
| |
Hi,
On 18/09/13 01:29, John Tapsell wrote: > Do not lock fb_info when calling sending the FB_EVENT_CONBLANK > event. > > In fbmem.c, the semantics are that we acquire the lock_fb_info first, > and then console_lock. However when fbcon.c fbcon_generic_blank() is > called, the console lock could already be held. Locking fb_info can > thus cause a deadlock.
So has this happened for you? Or is it just theoretical?
> fbmem.c sends the FB_EVENT_BLANK without locking lock_fb_info first, so > this change introduces similar behaviour.
I don't think this is true. FB_EVENT_BLANK is sent in fb_blank(). That one is called when FBIOBLANK ioctl is called, and it does lock_fb_info().
I'm not familiar with the console code, but removing a lock makes me feel rather uneasy... But looking at the code, I can also see that console_lock could already be held, so something here definitely looks broken.
The only place using FB_EVENT_CONBLANK seems to be backlight, and if I'm not mistaken, it has its own lock, and doesn't depend on the fb_info being locked.
Tomi
[unhandled content-type:application/pgp-signature] | |