linux-kernel - Re: [PATCH v6 2/2] misc: Add a mechanism to detect stalls on guest vCPUs

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Date:   Thu, 16 Jun 2022 16:05:04 +0000
From:   Sebastian Ene <sebastianene@...gle.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Rob Herring <robh+dt@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Dragan Cvetic <dragan.cvetic@...inx.com>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        maz@...nel.org, will@...nel.org, vdonnefort@...gle.com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v6 2/2] misc: Add a mechanism to detect stalls on guest
 vCPUs

On Thu, Jun 16, 2022 at 06:08:51AM -0700, Guenter Roeck wrote:
> On 6/16/22 03:08, Greg Kroah-Hartman wrote:
> > On Thu, Jun 16, 2022 at 09:27:39AM +0000, Sebastian Ene wrote:
> > > This driver creates per-cpu hrtimers which are required to do the
> > > periodic 'pet' operation. On a conventional watchdog-core driver, the
> > > userspace is responsible for delivering the 'pet' events by writing to
> > > the particular /dev/watchdogN node. In this case we require a strong
> > > thread affinity to be able to account for lost time on a per vCPU.
> > > 
> > > This part of the driver is the 'frontend' which is reponsible for
> > > delivering the periodic 'pet' events, configuring the virtual peripheral
> > > and listening for cpu hotplug events. The other part of the driver
> > > handles the peripheral emulation and this part accounts for lost time by
> > > looking at the /proc/{}/task/{}/stat entries and is located here:
> > > https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3548817
> > > 
> > > Reported-by: kernel test robot <lkp@...el.com>
> > 
> > The robot reported stalls on vcpus?
> > 

Hi,

> 
> I have seen this a number of times when people fix issues reported by
> the robot in their submissions, just because the robot asks them to
> do so. This should really be part of the change log, such as
> 
> v17: Fixed the following issues issues reported by the kernel test robot:
>      ...
> 

I will add this in the changelog for v7.

> Guenter

Thanks,
Seb