linux-kernel - Re: rcu: BUG: spinlock recursion on CPU#3, trinity-child19/5970

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

Message-ID: <20120702113541.GI2907@linux.vnet.ibm.com>
Date:	Mon, 2 Jul 2012 04:35:41 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Sasha Levin <levinsasha928@...il.com>,
	Dave Jones <davej@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: rcu: BUG: spinlock recursion on CPU#3, trinity-child19/5970

On Mon, Jul 02, 2012 at 12:32:19PM +0200, Peter Zijlstra wrote:
> On Fri, 2012-06-29 at 23:40 +0200, Sasha Levin wrote:
> > 
> > The bad news are that what you saw was a lockdep enabled run
> > (CONFIG_PROVE_RCU is enabled, and lockdep was enabled). There were no
> > lockdep warnings at any point while reproducing it. 
> 
> rcu_switch_from() -> rcu_preempt_note_context_switch() is called _after_
> the lockdep context switch annotation. Therefore lockdep things the prev
> task isn't holding any locks anymore.

In other words, moving rcu_preempt_note_context_switch() deeper into
the scheduler is totally bogus, and I need to move it back out into the
original rcu_note_context_switch(), reverting 616c310e (Move PREEMPT_RCU
preemption to switch_to() invocation), correct?

Sigh.  "It seemed like a good idea at the time."

							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/