Re: [PATCH] printk deadlocks if called with runqueue lock held

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To: Steven Rostedt <rostedt@...>

Cc: LKML <linux-kernel@...>, Linus Torvalds <torvalds@...>, Andrew Morton <akpm@...>, Alexey Dobriyan <adobriyan@...>, Kirill Korotaev <dev@...>

Subject: Re: [PATCH] printk deadlocks if called with runqueue lock held

Date: Wednesday, January 23, 2008 - 9:31 am

Hi!

quoted text> I thought that one could place a printk anywhere without worrying.
> But it seems that it is not wise to place a printk where the runqueue
> lock is held.
> 
> I just spent two hours debugging why some of my code was locking up,
> to find that the lockup was caused by some debugging printk's that
> I had in the scheduler.  The printk's were only in rare paths so
> they shouldn't be too much of a problem, but after I hit the printk
> the system locked up.
> 
> Thinking that it was locking up on my code I went looking down the
> wrong path. I finally found (after examining an NMI dump) that
> the lockup happened because printk was trying to wakeup the klogd
> daemon, which caused a deadlock when the try_to_wakeup code tries
> to grab the runqueue lock.

Could try_to_wakeup use trylock, and only avoid wakeup if lock is
already held?
							Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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Messages in current thread:

[PATCH] printk deadlocks if called with runqueue lock held, Steven Rostedt, (Thu Jan 17, 9:04 pm)

Re: [PATCH] printk deadlocks if called with runqueue lock held, Pavel Machek, (Wed Jan 23, 9:31 am)

Re: [PATCH] printk deadlocks if called with runqueue lock held, Steven Rostedt, (Wed Jan 23, 2:36 pm)

Re: [PATCH] printk deadlocks if called with runqueue lock held, Pavel Machek, (Thu Jan 24, 5:00 am)

Re: [PATCH] printk deadlocks if called with runqueue lock held, Jiri Kosina, (Fri Jan 18, 7:04 am)

Re: [PATCH] printk deadlocks if called with runqueue lock held, Steven Rostedt, (Fri Jan 18, 7:35 am)

Re: [PATCH] printk deadlocks if called with runqueue lock held, Jan Kiszka, (Fri Jan 18, 10:55 am)

Re: [PATCH] printk deadlocks if called with runqueue lock held, Linus Torvalds, (Fri Jan 18, 1:30 pm)

Re: [PATCH] printk deadlocks if called with runqueue lock held, Steven Rostedt, (Fri Jan 18, 12:26 pm)

Re: [PATCH] printk deadlocks if called with runqueue lock held, Linus Torvalds, (Thu Jan 17, 9:31 pm)

Re: [PATCH] printk deadlocks if called with runqueue lock held, Steven Rostedt, (Thu Jan 17, 9:52 pm)

Re: [PATCH] printk deadlocks if called with runqueue lock held, Andrew Morton, (Thu Jan 17, 9:19 pm)

Re: [PATCH] printk deadlocks if called with runqueue lock held, Steven Rostedt, (Thu Jan 17, 9:57 pm)


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Re: [PATCH] printk deadlocks if called with runqueue lock held

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