Messages in this thread |  | | Subject | Re: [RFC PATCH 2/2] lib: debugobjects: touch watchdog to avoid softlockup when !CONFIG_PREEMPT | From | Waiman Long <> | Date | Mon, 27 Nov 2017 13:18:36 -0500 |
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On 11/27/2017 12:54 PM, Yang Shi wrote: > Hi Waiman, > > The second patch of this series. > > Thanks, > Yang > > > On 11/17/17 11:43 AM, Yang Shi wrote: >> There are nested loops on debug objects free path, sometimes it may take >> over hundred thousands of loops, then cause soft lockup with >> !CONFIG_PREEMPT >> occasionally, like below: >> >> ... >> >> The code path might be called in either atomic or non-atomic context, >> so touching softlockup watchdog instead of calling cond_resched() which >> might fall asleep. However, it is unnecessary to touch the watchdog >> every loop, so just touch the watchdog at every 10000 (best estimate) >> loops. >> >> Signed-off-by: Yang Shi <yang.s@alibaba-inc.com>
I do have some concern about suppressing the soft lockup warning entirely. If the system feels unresponsive for a certain period of time (e.g. 22s), most users would like to know what is going on. It can be a custom message with less scary warning. Alternatively, some opt-out mechanism can be added to explicitly disable soft lookup warning for debugobjs is OK as long as it is not the default.
Cheers, Longman
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