linux-kernel - Re: [PATCH] ARM64: smp: Silence suspicious RCU usage with ipi tracepoints

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Message-ID: <20150625132453.GA13892@localhost>
Date:	Thu, 25 Jun 2015 14:24:54 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Will Deacon <will.deacon@....com>,
	linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
	John Stultz <john.stultz@...aro.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM64: smp: Silence suspicious RCU usage with ipi
 tracepoints

On Wed, Jun 24, 2015 at 02:59:30PM -0700, Stephen Boyd wrote:
> On 06/24/2015 02:29 PM, Peter Zijlstra wrote:
> > On Wed, Jun 24, 2015 at 01:14:18PM -0700, Stephen Boyd wrote:
> >> John Stultz reported an RCU splat on ARM with ipi trace events
> >> enabled. It looks like the same problem exists on ARM64.
> >>
> >> At this point in the IPI handling path we haven't called
> >> irq_enter() yet, so RCU doesn't know that we're about to exit
> >> idle and properly warns that we're using RCU from an idle CPU.
> >> Use trace_ipi_entry_rcuidle() instead of trace_ipi_entry() so
> >> that RCU is informed about our exit from idle.
> > I have a problem with $subject. It says 'silence', whereas afaict this
> > fixes an actual bug, so it should be 'fixes'.
> 
> Fair enough. I can resend or whoever applies this patch can
> s/Silence/Fix/ on the $subject.

I'll apply the patch and change the subject as well.

Thanks.

-- 
Catalin
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