Messages in this thread Patch in this message | | | Date | Fri, 23 May 2014 10:34:55 +0200 | From | Vlastimil Babka <> | Subject | Re: [PATCH v2] mm, compaction: properly signal and act upon lock and need_sched() contention |
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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
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