netdev - Re: [PATCH] pkt_sched: Fix lockdep warning on est_tree_lock in gen

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Message-ID: <1283459521.3699.193.camel@edumazet-laptop>
Date:	Thu, 02 Sep 2010 22:32:01 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	jarkao2@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH] pkt_sched: Fix lockdep warning on est_tree_lock in
 gen_estimator

Le jeudi 02 septembre 2010 à 13:22 -0700, David Miller a écrit :
> From: Jarek Poplawski <jarkao2@...il.com>
> Date: Thu, 2 Sep 2010 22:12:58 +0200
> 
> > This patch fixes a lockdep warning:
> > 
> > [  516.287584] =========================================================
> > [  516.288386] [ INFO: possible irq lock inversion dependency detected ]
> > [  516.288386] 2.6.35b #7
> > [  516.288386] ---------------------------------------------------------
> > [  516.288386] swapper/0 just changed the state of lock:
> > [  516.288386]  (&qdisc_tx_lock){+.-...}, at: [<c12eacda>] est_timer+0x62/0x1b4
> > [  516.288386] but this lock took another, SOFTIRQ-unsafe lock in the past:
> > [  516.288386]  (est_tree_lock){+.+...}
> > [  516.288386] 
> > [  516.288386] and interrupts could create inverse lock ordering between them.
> > ...
> > 
> > So, est_tree_lock needs BH protection because it's taken by
> > qdisc_tx_lock, which is used both in BH and process contexts.
> > (Full warning with this patch at netdev, 02 Sep 2010.)
> > 
> > Fixes commit: ae638c47dc040b8def16d05dc6acdd527628f231
> > 
> > Signed-off-by: Jarek Poplawski <jarkao2@...il.com>
> 
> Applied, thanks Jarek.
> 
> Eric, please make an effort to run with lockdep enabled when making
> locking changes, just for fun :-)

Hmm... I still trying to understand the problem.

I dont understand Jarek analysis yet.


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