linux-kernel - Re: [PATCH][RFC] PM / Hibernate: Feed NMI wathdog when creating snapshot

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Message-ID: <20170816111731.GA32161@dhcp22.suse.cz>
Date:   Wed, 16 Aug 2017 13:17:32 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Chen Yu <yu.c.chen@...el.com>
Cc:     linux-mm@...ck.org, linux-pm@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>,
        linux-kernel@...r.kernel.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH][RFC] PM / Hibernate: Feed NMI wathdog when creating
 snapshot

On Wed 16-08-17 00:01:08, Chen Yu wrote:
> Hi Michal,
> On Tue, Aug 15, 2017 at 02:41:19PM +0200, Michal Hocko wrote:
[...]
> > Moreover why don't you need to touch_nmi_watchdog in the loop over all
> > pfns in the zone (right above this loop)?
> As the NMI was triggered when checking the free_list rather than in the loop over
> all pfns, it seems that the former has more possibility to catch a NMI if the
> latter has already taken too much time. But yes, a safer way is to feed dog
> in the latter too. I'll modify the code according to your suggestion.

This is a wrong approach IMHO. The whole thing has IRQ disabled.

-- 
Michal Hocko
SUSE Labs