| Message ID | 537F082F.50501@suse.cz (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, May 23, 2014 at 10:34:55AM +0200, Vlastimil Babka wrote: > 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> Tested-by: Shawn Guo <shawn.guo@linaro.org> > --- > 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 > >
Vlastimil Babka <vbabka@suse.cz> writes: > 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> Tested-by: Kevin Hilman <khilman@linaro.org> I verified that this fixes the boot failures I've seen on ARM (i.MX6 and Marvell Armada 370). Thanks for the quick fix. Kevin
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:-(
Vlastimil, On Fri, May 23, 2014 at 5:34 AM, Vlastimil Babka <vbabka@suse.cz> wrote: > 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; > } This patch is still not in linux-next. Could you please submit it formally?
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 */