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From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Viresh Kumar <viresh.kumar@linaro.org>,
	Josh Boyer <jwboyer@fedoraproject.org>
Cc: Dirk Brandewie <dirk.brandewie@gmail.com>,
	"cpufreq@vger.kernel.org" <cpufreq@vger.kernel.org>,
	Linux PM list <linux-pm@vger.kernel.org>,
	"Linux-Kernel@Vger. Kernel. Org" <linux-kernel@vger.kernel.org>
Subject: Re: intel_pstate divide error with v3.13-rc4-256-gb7000ad
Date: Fri, 27 Dec 2013 15:35:29 +0100
Message-ID: <2312220.jMindkoXyA@vostro.rjw.lan> (raw)
In-Reply-To: <CAKohpomqHApogDEXA5LyWk-+B-Y1mwNQ63-wL3PPGz64s_3Dmw@mail.gmail.com>

On Tuesday, December 24, 2013 09:36:01 PM Viresh Kumar wrote:
> Adding Dirk..
> 
> On 24 December 2013 20:06, Josh Boyer <jwboyer@fedoraproject.org> wrote:
> > Hi All,
> >
> > We've had a report [1] that the pstate driver causes KVM guests to
> > fail to boot because of a divide error.  See the backtrace below.
> >
> >     4.839784] Intel P-state driver initializing.
> > [    4.859972] Intel pstate controlling: cpu 0
> > [    4.867653] cpufreq: __cpufreq_add_dev: ->get() failed
> 
> After a call to ->init(), ->get() is supposed to work.
> @Dirk: Any idea why it failed?

Well, it looks like sample->freq is 0 in intel_pstate_get().

> And then I don't know what made this divide by zero to happen :)

>From code inspection it looks like that is caused by the
intel_pstate_get_scaled_busy() called from intel_pstate_adjust_busy_pstate(),
so it appears that cpu->pstate.current_state is 0 at that point.

I'm wondering if something like the (untested) patch below helps, then?

Rafael


---
 drivers/cpufreq/intel_pstate.c |    5 +++++
 1 file changed, 5 insertions(+)

Index: linux-pm/drivers/cpufreq/intel_pstate.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/intel_pstate.c
+++ linux-pm/drivers/cpufreq/intel_pstate.c
@@ -652,6 +652,11 @@ static int intel_pstate_init_cpu(unsigne
 	cpu = all_cpu_data[cpunum];
 
 	intel_pstate_get_cpu_pstates(cpu);
+	if (!cpu->pstate.current_state) {
+		all_cpu_data[cpunum] = NULL;
+		kfree(cpu);
+		return -ENODATA;
+	}
 
 	cpu->cpu = cpunum;
 


      parent reply index

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-12-24 14:36 Josh Boyer
2013-12-24 16:06 ` Viresh Kumar
2013-12-27 12:24   ` One Thousand Gnomes
2013-12-27 12:47     ` Gleb Natapov
2013-12-27 13:46       ` Josh Boyer
2013-12-27 14:15         ` Kashyap Chamarthy
2013-12-27 14:34           ` Richard W.M. Jones
2013-12-27 16:52           ` Gleb Natapov
2013-12-27 17:01             ` Gleb Natapov
2013-12-27 17:17               ` Richard W.M. Jones
2013-12-27 17:17               ` Kashyap Chamarthy
2013-12-27 21:51                 ` Rafael J. Wysocki
2013-12-29 12:12                   ` Kashyap Chamarthy
2013-12-29 15:04                     ` Rafael J. Wysocki
2013-12-30 14:58                       ` Kashyap Chamarthy
2013-12-31  2:07                         ` Rafael J. Wysocki
2014-01-03 17:30                           ` Dirk Brandewie
2014-01-03 18:04                             ` Gleb Natapov
2014-01-03 20:00                               ` Dirk Brandewie
2014-01-03 22:06                                 ` Paolo Bonzini
2014-01-06 17:18                                   ` Dirk Brandewie
2014-01-07 16:11                                     ` Gleb Natapov
2014-01-03 22:46                               ` Rafael J. Wysocki
2014-01-04  8:35                                 ` Paolo Bonzini
2014-01-04 14:38                                   ` Rafael J. Wysocki
2014-01-04 17:38                                     ` Paolo Bonzini
2014-01-04 17:48                                       ` Gleb Natapov
2014-01-04 21:38                                         ` Rafael J. Wysocki
2014-01-06 11:20                                           ` Paolo Bonzini
2014-01-06 11:37                                             ` Rafael J. Wysocki
2014-01-06 18:40                                               ` Dirk Brandewie
2013-12-27 14:35   ` Rafael J. Wysocki [this message]

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