Re: BUG: scheduling while atomic: cron/668/0x10c9a0c0 (was: Re: mm, page_alloc: avoid looking up the first zone in a zonelist twice)

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Mel,

On Mon, May 30, 2016 at 5:56 PM, Mel Gorman <mgorman@techsingularity.net> wrote:
> On Mon, May 30, 2016 at 03:13:40PM +0200, Geert Uytterhoeven wrote:
>> >     The benefit is negligible and the results are within the noise but each
>> >     cycle counts.
>> >
>> >     Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
>> >     Cc: Vlastimil Babka <vbabka@suse.cz>
>> >     Cc: Jesper Dangaard Brouer <brouer@redhat.com>
>> >     Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
>> >     Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
>>
>> About one week ago, I started seeing an obscure intermittent crash during
>> system shutdown on m68k/ARAnyM using atari_defconfig.
>> The crash isn't 100% reproducible, but it happens during ca. 1 out of 5
>> shutdowns.
>>
>> I finally managed to bisect it to the above commit.
>> I did verify that the parent commit didn't crash after 60 tries.
>> Unfortunately I couldn't revert the offending commit on top of v4.7-rc1, due to
>> conflicting changes.
>>
>> Do you have any idea what's going wrong?
>
> There isn't anything obvious from the crash log you showed but can you
> try the following just in case?
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index dba8cfd0b2d6..f2c1e47adc11 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3232,6 +3232,9 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
>                  * allocations are system rather than user orientated
>                  */
>                 ac->zonelist = node_zonelist(numa_node_id(), gfp_mask);
> +               ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
> +                                       ac->high_zoneidx, ac->nodemask);
> +               ac->classzone_idx = zonelist_zone_idx(ac->preferred_zoneref);
>                 page = get_page_from_freelist(gfp_mask, order,
>                                                 ALLOC_NO_WATERMARKS, ac);
>                 if (page)

Thanks, but unfortunately it doesn't help.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds