linux-kernel - Re: [PATCH v2 1/2] sched/debug: fix /proc/sched

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Message-ID: <20160607175818.jythl5pdqp3xzazi@treble>
Date:	Tue, 7 Jun 2016 12:58:18 -0500
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Mel Gorman <mgorman@...hsingularity.net>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Subject: Re: [PATCH v2 1/2] sched/debug: fix /proc/sched_debug regression

On Tue, Jun 07, 2016 at 02:47:57PM +0100, Mel Gorman wrote:
> On Fri, Jun 03, 2016 at 05:58:40PM -0500, Josh Poimboeuf wrote:
> > Commit cb2517653fcc ("sched/debug: Make schedstats a runtime tunable
> > that is disabled by default") introduced a bug when CONFIG_SCHEDSTATS is
> > enabled and the runtime tunable is disabled (which is the default).  The
> > wait-time, sum-exec, and sum-sleep fields are missing from the
> > /proc/sched_debug file in the runnable_tasks section.
> > 
> 
> I take it that this breaks userspace parsing?

In theory, yes, though I don't know if there are any tools out there
which parse it.

> > Fix it with a new schedstat_val() macro which returns the field value
> > when schedstats is enabled and zero otherwise.  The macro works with
> > both SCHEDSTATS and !SCHEDSTATS.  I put the macro in stats.h since it
> > might end up being useful in other places.
> > 
> > Fixes: cb2517653fcc ("sched/debug: Make schedstats a runtime tunable that is disabled by default")
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
> 
> Acked-by: Mel Gorman <mgorman@...hsingularity.net>

Thanks!

-- 
Josh