linux-kernel - Re: [v4.9-rt][report] stress-ng: possible circular locking dependency detected

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Date:   Tue, 19 Dec 2017 09:39:49 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Grygorii Strashko <grygorii.strashko@...com>,
        linux-rt-users <linux-rt-users@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, Sekhar Nori <nsekhar@...com>
Subject: Re: [v4.9-rt][report] stress-ng: possible circular locking
 dependency detected

On 2017-12-18 20:06:12 [-0500], Steven Rostedt wrote:
> On Mon, 18 Dec 2017 18:55:24 -0600
> Grygorii Strashko <grygorii.strashko@...com> wrote:
> 
> > Hi All,
> > 
> > I've tried to run stress-ng on TI am57xx-evm (SMP, 2 cpu) and caught 2  "INFO: possible circular locking dependency detected"
> > 
> > Command 1 (log 1):
> > ## stress-ng --class cpu --all 0 -t 5m &   stress-ng --class memory --all 0 --vm-bytes 90% -t 5m
> > 
> > Command 2 (log 2):
> > ## stress-ng --class os --all 0 -t 5m
> > 
> > actually command 2 often stuck or crushes (Log3 - I've collected 3 different dumps)
> > 
> 
> I hate to tell you but CPU hotplug is known to be broken on 4.9-rt and
> earlier. Hopefully the v4.14-rt code with the redesigned hotplug work
> fixes all this.

Yes, the v4.9-RT hotplug is not perfect. It works in general but can
fall apart with some load or "just" deadlock during CPU-down.
The v4.14-RT should not suffer from this and work.

> -- Steve

Sebastian