On 2021-05-24 09:33, Guenter Roeck wrote:
On 5/23/21 7:38 PM, Sai Prakash Ranjan wrote:
On 2021-04-20 11:13, Sai Prakash Ranjan wrote:
Hi Guenter,
On 2021-03-11 01:53, Guenter Roeck wrote:
On Thu, Mar 11, 2021 at 01:50:04AM +0530, Sai Prakash Ranjan wrote:
During suspend/resume usecases and tests, it is common to see
issues
such as lockups either in suspend path or resume path because of
the
bugs in the corresponding device driver pm handling code. In such
cases,
it is important that watchdog is active to make sure that we either
receive a watchdog pretimeout notification or a bite causing reset
instead of a hang causing us to hard reset the machine.
There are good reasons as to why we need this because:
* We can have a watchdog pretimeout governor set to panic in which
case we can have a backtrace which would help identify the issue
with the particular driver and cause a normal reboot.
* Even in case where there is no pretimeout support, a watchdog
bite is still useful because some firmware has debug support to
dump
CPU core context on watchdog bite for post-mortem analysis.
* One more usecase which comes to mind is of warm reboot. In case
we
hard reset the target, a cold reboot could be induced resulting
in
lose of ddr contents thereby losing all the debug info.
Currently, the watchdog pm callback just invokes the usual suspend
and resume callback which do not have any special ordering in the
sense that a watchdog can be suspended before the buggy device
driver
suspend callback and watchdog resume can happen after the buggy
device
driver resume callback. This would mean that the watchdog will not
be
active when the buggy driver cause the lockups thereby hanging the
system. So to make sure this doesn't happen, move the watchdog pm
to
use late/early system pm callbacks which will ensure that the
watchdog
is suspended late and resumed early so that it can catch such
issues.
Signed-off-by: Sai Prakash Ranjan
<saiprakash.ranjan@xxxxxxxxxxxxxx>
Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Gentle Ping. I don't see this in linux-next or linux-watchdog, please
let
me know if anything is pending from my side.
Gentle Ping !!
It is my watchdog-next branch. At some point Wim will hopefully pick it
up.
Ah I see, thanks for the info.
-Sai
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