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

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Message-ID: <20160607134757.GC2527@techsingularity.net>
Date:	Tue, 7 Jun 2016 14:47:57 +0100
From:	Mel Gorman <mgorman@...hsingularity.net>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
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 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?

> 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>

-- 
Mel Gorman
SUSE Labs