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

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Message-ID: <7dadb147-bf8a-d2b3-1f02-18b467492e5e@roeck-us.net>
Date:   Thu, 16 Jun 2022 09:09:18 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Sebastian Ene <sebastianene@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
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
Subject: Re: [PATCH v6 2/2] misc: Add a mechanism to detect stalls on guest
 vCPUs

On 6/16/22 09:01, Sebastian Ene wrote:
> On Thu, Jun 16, 2022 at 12:08:55PM +0200, 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>
>>
> 
> Hi,
> 
>> The robot reported stalls on vcpus?
>>
>> I think you need to fix this up...
> 
> The robot reported some issues on v5 and after fixing them it
> recommended to add this tag.
> 

Only that doesn't make sense for patch sets which are still being worked
on. If you want to credit the robot, mention it in the change log.

Guenter