linux-kernel - Re: RCU stall when using function

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Message-ID: <20170816124140.0b4b10e3@gandalf.local.home>
Date:   Wed, 16 Aug 2017 12:41:40 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Pratyush Anand <panand@...hat.com>,
        김동현 <austinkernel.kim@...il.com>,
        john.stultz@...aro.org, linux-kernel@...r.kernel.org
Subject: Re: RCU stall when using function_graph

On Wed, 16 Aug 2017 09:32:28 -0700
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> wrote:

> Let me see if I understand you...  About halfway to the stall limit,
> RCU triggers an irq_work (on each CPU that has not yet passed through
> a quiescent state, IPIing them in turn?), and if the irq_work has
> not completed by the end of the stall limit, RCU adds that to its
> stall-warning message.

Doesn't even have to be half way through. It could be done at the
limit, and then wait a little more.

> 
> Or am I missing something here?

No, I think that's what I was suggesting.

-- Steve