From: vbabka@suse•cz (Vlastimil Babka)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v2] mm, compaction: properly signal and act upon lock and need_sched() contention
Date: Fri, 23 May 2014 10:34:55 +0200 [thread overview]
Message-ID: <537F082F.50501@suse.cz> (raw)
In-Reply-To: <CAAQ0ZWQDVxAzZVm86ATXd1JGUVoLXj_Y5Ske7htxH_6a4GPKRg@mail.gmail.com>
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.
Signed-off-by: Vlastimil Babka <vbabka@suse•cz>
---
mm/compaction.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index a525cd4..5175019 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -237,13 +237,13 @@ static inline bool compact_should_abort(struct compact_control *cc)
if (need_resched()) {
if (cc->mode == MIGRATE_ASYNC) {
cc->contended = true;
- return false;
+ return true;
}
cond_resched();
}
- return true;
+ return false;
}
/* Returns true if the page is within a block suitable for migration to */
--
1.8.4.5
next prev parent reply other threads:[~2014-05-23 8:34 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 [this message]
2014-05-23 10:49 ` Shawn Guo
2014-05-23 15:07 ` Kevin Hilman
2014-05-30 16:59 ` Stephen Warren
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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