Messages in this thread | | | Date | Mon, 24 May 2021 09:42:09 +0530 | From | Sai Prakash Ranjan <> | Subject | Re: [PATCH] watchdog: qcom: Move suspend/resume to suspend_late/resume_early |
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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@codeaurora.org> >>>> >>>> Reviewed-by: Guenter Roeck <linux@roeck-us.net> >>>> >>> >>> 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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