From: Guenter Roeck <firstname.lastname@example.org> To: Sai Prakash Ranjan <email@example.com> Cc: Andy Gross <firstname.lastname@example.org>, Bjorn Andersson <email@example.com>, Douglas Anderson <firstname.lastname@example.org>, Wim Van Sebroeck <email@example.com>, firstname.lastname@example.org, Stephen Boyd <email@example.com>, Matthias Kaehlcke <firstname.lastname@example.org>, email@example.com, firstname.lastname@example.org, email@example.com, Guenter Roeck <firstname.lastname@example.org> Subject: Re: [PATCH] watchdog: qcom: Move suspend/resume to suspend_late/resume_early Date: Sun, 23 May 2021 21:03:20 -0700 [thread overview] Message-ID: <email@example.com> (raw) In-Reply-To: <firstname.lastname@example.org> 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 <email@example.com> >>> >>> Reviewed-by: Guenter Roeck <firstname.lastname@example.org> >>> >> >> 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. Guenter
next prev parent reply other threads:[~2021-05-24 4:03 UTC|newest] Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-03-10 20:20 Sai Prakash Ranjan 2021-03-10 20:23 ` Guenter Roeck 2021-04-20 5:43 ` Sai Prakash Ranjan 2021-05-24 2:38 ` Sai Prakash Ranjan 2021-05-24 4:03 ` Guenter Roeck [this message] 2021-05-24 4:12 ` Sai Prakash Ranjan 2021-03-10 20:27 ` Doug Anderson
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