linux-kernel - Re: perf related lockdep bug

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Message-ID: <20151104153651.GC11639@twins.programming.kicks-ass.net>
Date:	Wed, 4 Nov 2015 16:36:51 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Dave Jones <davej@...emonkey.org.uk>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Stephane Eranian <eranian@...il.com>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: perf related lockdep bug

On Wed, Nov 04, 2015 at 03:20:58PM +0100, Peter Zijlstra wrote:
> On Wed, Nov 04, 2015 at 05:48:38AM -0800, Paul E. McKenney wrote:
> > This problem is caused by the IPI handler interrupting the RCU read-side
> > critical section.  One way to prevent the IPI from doing this is to
> > disable interrupts across the RCU read-side critical section instead
> > of merely disabling preemption.  This is a reasonable approach given
> > that acquiring the scheduler locks is going to disable interrupts
> > in any case.
> > 
> > The (untested) patch below takes this approach.
> > 
> > Thoughts?
> 
> Yes, this should work, but now I worry I need to go audit all of perf
> and sched for this :/

I can't find any other sites just now, so let me queue this.

I also had a brief look if you used any other locks under rnp->lock, but
aside from the printk and sched things it seems clean.


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