From: swarren@wwwdotorg•org (Stephen Warren)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v2] mm, compaction: properly signal and act upon lock and need_sched() contention
Date: Fri, 30 May 2014 10:59:03 -0600 [thread overview]
Message-ID: <5388B8D7.1020907@wwwdotorg.org> (raw)
In-Reply-To: <537F082F.50501@suse.cz>
On 05/23/2014 02:34 AM, Vlastimil Babka wrote:
> On 05/23/2014 04:48 AM, Shawn Guo wrote:
>> On 23 May 2014 07:49, Kevin Hilman <khilman@linaro•org> wrote:
>>> On Fri, May 16, 2014 at 2:47 AM, Vlastimil Babka <vbabka@suse•cz> wrote:
>>>> Compaction uses compact_checklock_irqsave() function to periodically check for
>>>> lock contention and need_resched() to either abort async compaction, or to
>>>> free the lock, schedule and retake the lock. When aborting, cc->contended is
>>>> set to signal the contended state to the caller. Two problems have been
>>>> identified in this mechanism.
>>>
>>> This patch (or later version) has hit next-20140522 (in the form
>>> commit 645ceea9331bfd851bc21eea456dda27862a10f4) and according to my
>>> bisect, appears to be the culprit of several boot failures on ARM
>>> platforms.
>>
>> On i.MX6 where CMA is enabled, the commit causes the drivers calling
>> dma_alloc_coherent() fail to probe. Tracing it a little bit, it seems
>> dma_alloc_from_contiguous() always return page as NULL after this
>> commit.
>>
>> Shawn
>>
>
> Really sorry, guys :/
>
> -----8<-----
> From: Vlastimil Babka <vbabka@suse•cz>
> Date: Fri, 23 May 2014 10:18:56 +0200
> Subject: mm-compaction-properly-signal-and-act-upon-lock-and-need_sched-contention-fix2
>
> Step 1: Change function name and comment between v1 and v2 so that the return
> value signals the opposite thing.
> Step 2: Change the call sites to reflect the opposite return value.
> Step 3: ???
> Step 4: Make a complete fool of yourself.
Tested-by: Stephen Warren <swarren@nvidia•com>
This fix doesn't seem to be in linux-next yet:-(
next prev parent reply other threads:[~2014-05-30 16:59 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1399904111-23520-1-git-send-email-vbabka@suse.cz>
[not found] ` <1400233673-11477-1-git-send-email-vbabka@suse.cz>
[not found] ` <CAGa+x87-NRyK6kUiXNL_bRNEGm+DR6M3HPSLYEoq4t6Nrtnd_g@mail.gmail.com>
2014-05-23 2:48 ` [PATCH v2] mm, compaction: properly signal and act upon lock and need_sched() contention Shawn Guo
2014-05-23 8:34 ` Vlastimil Babka
2014-05-23 10:49 ` Shawn Guo
2014-05-23 15:07 ` Kevin Hilman
2014-05-30 16:59 ` Stephen Warren [this message]
2014-06-02 13:35 ` Fabio Estevam
2014-06-02 14:33 ` [PATCH -mm] mm, compaction: properly signal and act upon lock and need_sched() contention - fix Vlastimil Babka
2014-06-02 15:18 ` Fabio Estevam
2014-06-02 20:09 ` David Rientjes
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