From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
john.stultz@linaro.org, linux-kernel@vger.kernel.org,
Pratyush Anand <panand@redhat.com>
Subject: Re: RCU stall when using function_graph
Date: Thu, 3 Aug 2017 16:38:01 +0200 [thread overview]
Message-ID: <20170803143801.GE1919@mai> (raw)
In-Reply-To: <20170803124421.GP3730@linux.vnet.ibm.com>
On Thu, Aug 03, 2017 at 05:44:21AM -0700, Paul E. McKenney wrote:
[ ... ]
> > > BTW, function_graph tracer is the most invasive of the tracers. It's 4x
> > > slower than function tracer. I'm wondering if the tracer isn't the
> > > cause, but just slows things down enough to cause a some other race
> > > condition that triggers the bug.
> >
> > Yes, that could be true.
> >
> > I tried the following scenario:
> >
> > - cpufreq governor => userspace + max_freq (1.2GHz)
> > - function_graph set ==> OK
> >
> > - cpufreq governor => userspace + min_freq (200MHz)
> > - function_graph set ==> RCU stall
> >
> > Beside that, I realize the board is constantly processing SOF interrupts
> > every 124us, so that adds more overhead.
> >
> > Removing the USB support, thus the associated processing for the SOF
> > interrupts, I don't see anymore the RCU stall.
>
> Looks like Steve called this one! ;-)
Yep :)
> > Is it the expected behavior to have the system hang after a RCU stall
> > raises ?
>
> No, but if NMI stack traces are enabled and there are any NMI problems,
> bad things can happen. In addition, the bulk of output can cause problems
> if you have a slow console connection.
Ok, thanks.
-- Daniel
--
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next prev parent reply other threads:[~2017-08-03 14:38 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-01 22:04 RCU stall when using function_graph Paul E. McKenney
2017-08-01 22:15 ` Daniel Lezcano
2017-08-02 0:12 ` Steven Rostedt
2017-08-02 12:42 ` Daniel Lezcano
2017-08-02 13:07 ` Steven Rostedt
2017-08-03 2:40 ` Paul E. McKenney
2017-08-03 11:41 ` Daniel Lezcano
2017-08-03 12:44 ` Paul E. McKenney
2017-08-03 14:38 ` Daniel Lezcano [this message]
[not found] ` <CAOoBcBXo-=VYy2+TYEp=8+WSkOpDBr1x6uY=-r_GnTFKctXndQ@mail.gmail.com>
[not found] ` <CAOoBcBVKpQkAVXji5qQu8r8GErqxpy9Ae9N97NhGpOQPgXudZg@mail.gmail.com>
[not found] ` <CAOoBcBU00VRXmrNNEOjJHgXf9BimxKYOorJC0d3766mNdda=Bg@mail.gmail.com>
2017-08-06 17:02 ` Paul E. McKenney
2017-08-09 9:13 ` Pratyush Anand
2017-08-09 12:58 ` Paul E. McKenney
2017-08-09 13:28 ` Daniel Lezcano
2017-08-09 14:40 ` Paul E. McKenney
2017-08-09 15:51 ` Daniel Lezcano
2017-08-09 17:22 ` Paul E. McKenney
2017-08-10 9:45 ` Daniel Lezcano
2017-08-10 21:39 ` Paul E. McKenney
2017-08-11 9:38 ` Daniel Lezcano
2017-08-15 13:29 ` Steven Rostedt
2017-08-16 8:42 ` Daniel Lezcano
2017-08-16 14:04 ` Steven Rostedt
2017-08-16 16:32 ` Paul E. McKenney
2017-08-16 16:41 ` Steven Rostedt
2017-08-16 17:58 ` Paul E. McKenney
2017-08-30 22:07 ` Paul E. McKenney
2017-08-02 16:51 ` Paul E. McKenney
2017-08-02 12:49 ` Paul E. McKenney
-- strict thread matches above, loose matches on Subject: below --
2017-08-01 21:07 Daniel Lezcano
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