linux-kernel - Re: clocksource_watchdog causing scheduling of timers every second (was [v13] support "task

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Message-ID: <alpine.DEB.2.20.1607271452530.9567@east.gentwo.org>
Date:	Wed, 27 Jul 2016 14:53:47 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Chris Metcalf <cmetcalf@...lanox.com>
cc:	Gilad Ben Yossef <giladb@...lanox.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>, Tejun Heo <tj@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Andy Lutomirski <luto@...capital.net>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	linux-doc@...r.kernel.org, linux-api@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: clocksource_watchdog causing scheduling of timers every second
 (was [v13] support "task_isolation" mode)

On Wed, 27 Jul 2016, Chris Metcalf wrote:

> Looks good.  Did you omit the equivalent fix in clocksource_start_watchdog()
> on purpose?  For now I just took your change, but tweaked it to add the
> equivalent diff with cpumask_first_and() there.

Can the watchdog be started on an isolated cpu at all? I would expect that
the code would start a watchdog only on a housekeeping cpu.