Re: [PATCH] watchdog: nohz: don't run watchdog on nohz_full cores

From: Frederic Weisbecker
Date: Thu Apr 02 2015 - 12:48:56 EST

On Thu, Apr 02, 2015 at 11:42:43AM -0400, Chris Metcalf wrote:
> OK, I will respin v2 of the patch as follows:
> - Provide a watchdog_cpumask as suggested by Don.
> - On a non-NO_HZ_FULL build, it defaults to cpu_possible as normal
> - On a NO_HZ_FULL build, it defaults to the housekeeping cpus

Ah note that NO_HZ_FULL is only the capability. Nohz full is actually
only running if the nohz_full parameter is passed (or NO_HZ_FULL_ALL=y).

And now generalist distros enable NO_HZ_FULL so that anybody can use it.

So better check tick_nohz_full_enabled() instead of the CONFIG.


> - If the mask is modified, we disable and then re-enable the watchdog,
> so that the watchdog init code can exit() the appropriate threads as
> they start up
> This should address the various concerns that have been raised.
> --
> Chris Metcalf, EZChip Semiconductor
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