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SubjectRe: [PATCH 0/5] improve handling of errors returned by kthread_park()
On Mon, Sep 28, 2015 at 10:44:07PM +0200, Ulrich Obergfell wrote:
> The original watchdog_park_threads() function that was introduced by
> commit 81a4beef91ba4a9e8ad6054ca9933dff7e25ff28 takes a very simple
> approach to handle errors returned by kthread_park(): It attempts to
> roll back all watchdog threads to the unparked state. However, this
> may be undesired behaviour from the perspective of the caller which
> may want to handle errors as appropriate in its specific context.
> Currently, there are two possible call chains:


I spent a little time cleaning up some of my test scripts for this code.
Things seem to work well. Hardlockups and softlockups work along with
enabling/disabling the various lockup knobs.

Acked-by: Don Zickus <dzickus@redhat.com>

>
> - watchdog suspend/resume interface
>
> lockup_detector_suspend
> watchdog_park_threads
>
> - write to parameters in /proc/sys/kernel
>
> proc_watchdog_update
> watchdog_enable_all_cpus
> update_watchdog_all_cpus
> watchdog_park_threads
>
> Instead of 'blindly' attempting to unpark the watchdog threads if a
> kthread_park() call fails, the new approach is to disable the lockup
> detectors in the above call chains. Failure becomes visible to the
> user as follows:
>
> - error messages from lockup_detector_suspend()
> or watchdog_enable_all_cpus()
>
> - the state that can be read from /proc/sys/kernel/watchdog_enabled
>
> - the 'write' system call in the latter call chain returns an error
>
> Ulrich Obergfell (5):
> watchdog: fix error handling in proc_watchdog_thresh()
> watchdog: move watchdog_disable_all_cpus() outside of ifdef
> watchdog: implement error handling in update_watchdog_all_cpus() and
> callers
> watchdog: implement error handling in lockup_detector_suspend()
> watchdog: do not unpark threads in watchdog_park_threads() on error
>
> kernel/watchdog.c | 60 +++++++++++++++++++++++++++++++++++++++----------------
> 1 file changed, 43 insertions(+), 17 deletions(-)
>
> --
> 1.7.11.7
>


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