From: Sai Prakash Ranjan <email@example.com> To: Guenter Roeck <firstname.lastname@example.org> Cc: Andy Gross <email@example.com>, Bjorn Andersson <firstname.lastname@example.org>, Douglas Anderson <email@example.com>, Wim Van Sebroeck <firstname.lastname@example.org>, email@example.com, Stephen Boyd <firstname.lastname@example.org>, Matthias Kaehlcke <email@example.com>, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, Guenter Roeck <email@example.com> Subject: Re: [PATCH] watchdog: qcom: Move suspend/resume to suspend_late/resume_early Date: Mon, 24 May 2021 08:08:39 +0530 [thread overview] Message-ID: <firstname.lastname@example.org> (raw) In-Reply-To: <email@example.com> 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 <firstname.lastname@example.org> >> >> Reviewed-by: Guenter Roeck <email@example.com> >> > > 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 !! Thanks, Sai -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
next prev parent reply other threads:[~2021-05-24 2:38 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 [this message] 2021-05-24 4:03 ` Guenter Roeck 2021-05-24 4:12 ` Sai Prakash Ranjan 2021-03-10 20:27 ` Doug Anderson
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