On Mon, 28 Sep 2015 22:44:07 +0200 Ulrich Obergfell <uober...@redhat.com> 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: > > - 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 > hm, you made me look at kthread parking. Why does it exist? What is a "parked" thread anyway, and how does it differ from, say, a sleeping one? The 2a1d446019f9a5983ec5a335b changelog is pretty useless and the patch added no useful documentation, sigh. Anwyay... what inspired this patchset? Are you experiencing kthread_park() failures in practice? If so, what is causing them? And what is the user-visible effect of these failures? This is all pretty important context for such a patchset. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
