linux-kernel - Re: [PATCH V2 2/2] rt: Increase/decrease the nr of migratory tasks when enabling/disabling migration

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Message-ID: <998180d6-b4c5-bf04-1088-4d5055e4eaf1@redhat.com>
Date:   Tue, 27 Jun 2017 18:32:51 +0200
From:   Daniel Bristot de Oliveira <bristot@...hat.com>
To:     Henri Roosen <henri.roosen@...zinger.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        linux-rt-users <linux-rt-users@...r.kernel.org>
Cc:     "Luis Claudio R . Goncalves" <lgoncalv@...hat.com>,
        Clark Williams <williams@...hat.com>,
        Luiz Capitulino <lcapitulino@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2 2/2] rt: Increase/decrease the nr of migratory tasks
 when enabling/disabling migration



On 06/27/2017 04:55 PM, Henri Roosen wrote:
>>
>> As rt_nr_migratory is unsigned, it will become > 0, notifying that the
>> RQ is overloaded, activating pushing mechanism without need.
> 
> What kind of symptoms might be triggered by this? I'm currently facing a
> problem with a continuous-reboot-test where the kernel seems to hang
> sometimes at a (seemingly) random place during kernel boot, on
> 4.9.33-rt23 with iMX6Q. A back-port of this patch to 4.9-rt seems to fix
> it. Or is it covering up a different problem?

The side effect is notifying that the RQ is overloaded, activating
pushing mechanism without need.

I was not seeing system freezes because of it... but, just in case...do
you have the console output from your board?

-- Daniel