linux-kernel - Re: [PATCH] printk: robustify printk

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Message-ID: <Pine.LNX.4.64.0808201438490.18947@twin.jikos.cz>
Date:	Wed, 20 Aug 2008 14:40:55 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Ingo Molnar <mingo@...e.hu>
cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>, tglx@...utronix.de,
	marcin.slusarz@...il.com, linux-kernel@...r.kernel.org,
	davem@...emloft.net, rostedt@...dmis.org,
	paulmck@...ux.vnet.ibm.com
Subject: Re: [PATCH] printk: robustify printk

On Mon, 11 Aug 2008, Ingo Molnar wrote:

> ----------------->
> >From b845b517b5e3706a3729f6ea83b88ab85f0725b0 Mon Sep 17 00:00:00 2001
> From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Date: Fri, 8 Aug 2008 21:47:09 +0200
> Subject: [PATCH] printk: robustify printk
> 
> Avoid deadlocks against rq->lock and xtime_lock by deferring the klogd
> wakeup by polling from the timer tick.
> 
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Signed-off-by: Ingo Molnar <mingo@...e.hu>

Then I think we also want the patch below on top of that, right?


From: Jiri Kosina <jkosina@...e.cz>
printk: robustify printk, fix #3

Remove the comment describing the possibility of printk() deadlocking on 
runqueue lock.

Signed-off-by: Jiri Kosina <jkosina@...e.cz>

--- 

 kernel/printk.c |    3 ---
 1 files changed, 0 insertions(+), 3 deletions(-)

diff --git a/kernel/printk.c b/kernel/printk.c
index b51b156..9fbf391 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -577,9 +577,6 @@ static int have_callable_console(void)
  * @fmt: format string
  *
  * This is printk().  It can be called from any context.  We want it to work.
- * Be aware of the fact that if oops_in_progress is not set, we might try to
- * wake klogd up which could deadlock on runqueue lock if printk() is called
- * from scheduler code.
  *
  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
  * call the console drivers.  If we fail to get the semaphore we place the output
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