From: Mel Gorman <mgorman@techsingularity.net>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Vlastimil Babka <vbabka@suse.cz>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux MM <linux-mm@kvack.org>,
linux-m68k <linux-m68k@vger.kernel.org>
Subject: Re: BUG: scheduling while atomic: cron/668/0x10c9a0c0
Date: Fri, 3 Jun 2016 09:41:42 +0100 [thread overview]
Message-ID: <20160603084142.GY2527@techsingularity.net> (raw)
In-Reply-To: <CAMuHMdX07bUE+3QTbFmbxrjkXPBzFLoLQbupL=WAbLXTuN+6Ww@mail.gmail.com>
On Fri, Jun 03, 2016 at 09:57:22AM +0200, Geert Uytterhoeven wrote:
> Hi Andrew, Mel,
>
> On Thu, Jun 2, 2016 at 8:43 PM, Andrew Morton <akpm@linux-foundation.org> wrote:
> > On Thu, 2 Jun 2016 13:19:36 +0100 Mel Gorman <mgorman@techsingularity.net> wrote:
> >> > >Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> >> >
> >> > Acked-by: Vlastimil Babka <vbabka@suse.cz>
> >> >
> >>
> >> Thanks.
> >
> > I queued this. A tested-by:Geert would be nice?
> >
> >
> > From: Mel Gorman <mgorman@techsingularity.net>
> > Subject: mm, page_alloc: recalculate the preferred zoneref if the context can ignore memory policies
> >
> > The optimistic fast path may use cpuset_current_mems_allowed instead of of
> > a NULL nodemask supplied by the caller for cpuset allocations. The
> > preferred zone is calculated on this basis for statistic purposes and as a
> > starting point in the zonelist iterator.
> >
> > However, if the context can ignore memory policies due to being atomic or
> > being able to ignore watermarks then the starting point in the zonelist
> > iterator is no longer correct. This patch resets the zonelist iterator in
> > the allocator slowpath if the context can ignore memory policies. This
> > will alter the zone used for statistics but only after it is known that it
> > makes sense for that context. Resetting it before entering the slowpath
> > would potentially allow an ALLOC_CPUSET allocation to be accounted for
> > against the wrong zone. Note that while nodemask is not explicitly set to
> > the original nodemask, it would only have been overwritten if
> > cpuset_enabled() and it was reset before the slowpath was entered.
> >
> > Link: http://lkml.kernel.org/r/20160602103936.GU2527@techsingularity.net
> > Fixes: c33d6c06f60f710 ("mm, page_alloc: avoid looking up the first zone in a zonelist twice")
>
> My understanding was that this was an an additional patch, not fixing
> the problem in-se?
>
It doesn't fix the problem you had, it is a follow-on patch that
potentially affects.
> Indeed, after applying this patch (without the other one that added
> "z = ac->preferred_zoneref;" to the reset_fair block of
> get_page_from_freelist()) I still get crashes...
>
The patch you have is the only one required for the crash. This patch
handles a corner case with atomic allocations that can ignore memory
policies.
> Now testing with both applied...
Thanks.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2016-06-03 8:41 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-30 13:13 BUG: scheduling while atomic: cron/668/0x10c9a0c0 (was: Re: mm, page_alloc: avoid looking up the first zone in a zonelist twice) Geert Uytterhoeven
2016-05-30 15:56 ` Mel Gorman
2016-05-30 17:37 ` Geert Uytterhoeven
2016-05-30 18:56 ` Mel Gorman
2016-05-31 9:28 ` Geert Uytterhoeven
2016-05-31 10:13 ` Mel Gorman
2016-05-31 21:44 ` Vlastimil Babka
2016-06-01 9:19 ` Mel Gorman
2016-06-01 10:01 ` BUG: scheduling while atomic: cron/668/0x10c9a0c0 Vlastimil Babka
2016-06-02 10:39 ` Mel Gorman
2016-06-02 12:04 ` Vlastimil Babka
2016-06-02 12:19 ` Mel Gorman
2016-06-02 18:43 ` Andrew Morton
2016-06-03 3:52 ` Stephen Rothwell
2016-06-03 7:57 ` Geert Uytterhoeven
2016-06-03 8:41 ` Mel Gorman [this message]
2016-06-03 9:00 ` Geert Uytterhoeven
2016-06-03 16:35 ` Andrew Morton
2016-06-03 16:46 ` Mel Gorman
2016-06-03 16:49 ` Andrew Morton
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