linux-kernel - Re: lockdep circular locking error (rcu_node_level

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20110714052622.GA5366@linux.vnet.ibm.com>
Date:	Wed, 13 Jul 2011 22:26:22 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: lockdep circular locking error (rcu_node_level_0 vs rq->lock)

On Wed, Jul 13, 2011 at 09:29:32PM -0700, Paul E. McKenney wrote:
> On Wed, Jul 13, 2011 at 09:33:09AM -0700, Paul E. McKenney wrote:

[ . . . ]

> Hmmm...  Something is confused.  I get boot time hangs with the
> occasional stack overflow, whether or not I add my patch on top.
> Left to myself, I would try applying your patch incrementally, and
> also disabling irqs before rcu_read_lock() and enabling them after
> rcu_read_unlock(), as this prevents rcu_read_unlock() from ever getting
> to the rcu_read_unlock_special() slowpath.

And the real question...  Why did the rcu_read_unlock() called from
cpuacct_charge() enter rcu_read_unlock_special() in the first place?
If the runqueue lock is held, irqs should be disabled, so how did the
task get blocked or interrupted?

I need to get some sleep then figure out what is going on here.

							Thanx, Paul
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/