[PATCH] slab: fix the DEADLOCK issue on l3 alien lock

[PATCH] slab: fix the DEADLOCK issue on l3 alien lock

[Michael Wang]

From: Michael Wang <wangyun@linux.vnet.ibm.com>

DEADLOCK will be report while running a kernel with NUMA and LOCKDEP enabled,
the process of this fake report is:

	   kmem_cache_free()	//free obj in cachep
	-> cache_free_alien()	//acquire cachep's l3 alien lock
	-> __drain_alien_cache()
	-> free_block()
	-> slab_destroy()
	-> kmem_cache_free()	//free slab in cachep->slabp_cache
	-> cache_free_alien()	//acquire cachep->slabp_cache's l3 alien lock

Since the cachep and cachep->slabp_cache's l3 alien are in the same lock class,
fake report generated.

This should not happen since we already have init_lock_keys() which will
reassign the lock class for both l3 list and l3 alien.

However, init_lock_keys() was invoked at a wrong position which is before we
invoke enable_cpucache() on each cache.

Since until set slab_state to be FULL, we won't invoke enable_cpucache()
on caches to build their l3 alien while creating them, so although we invoked
init_lock_keys(), the l3 alien lock class won't change since we don't have
them until invoked enable_cpucache() later.

This patch will invoke init_lock_keys() after we done enable_cpucache()
instead of before to avoid the fake DEADLOCK report.

Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
---
 mm/slab.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index d4715e5..cc679ef 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1780,9 +1780,6 @@ void __init kmem_cache_init_late(void)
 
 	slab_state = UP;
 
-	/* Annotate slab for lockdep -- annotate the malloc caches */
-	init_lock_keys();
-
 	/* 6) resize the head arrays to their final sizes */
 	mutex_lock(&slab_mutex);
 	list_for_each_entry(cachep, &slab_caches, list)
@@ -1790,6 +1787,9 @@ void __init kmem_cache_init_late(void)
 			BUG();
 	mutex_unlock(&slab_mutex);
 
+	/* Annotate slab for lockdep -- annotate the malloc caches */
+	init_lock_keys();
+
 	/* Done! */
 	slab_state = FULL;
 
-- 
1.7.4.1

Re: [PATCH] slab: fix the DEADLOCK issue on l3 alien lock

[Christoph Lameter]

On Wed, 5 Sep 2012, Michael Wang wrote:

> Since the cachep and cachep->slabp_cache's l3 alien are in the same lock class,
> fake report generated.

Ahh... That is a key insight into why this occurs.

> This should not happen since we already have init_lock_keys() which will
> reassign the lock class for both l3 list and l3 alien.

Right. I was wondering why we still get intermitted reports on this.

> This patch will invoke init_lock_keys() after we done enable_cpucache()
> instead of before to avoid the fake DEADLOCK report.

Acked-by: Christoph Lameter <cl@linux.com>

Re: [PATCH] slab: fix the DEADLOCK issue on l3 alien lock

[Michael Wang]

On 09/05/2012 09:55 PM, Christoph Lameter wrote:
> On Wed, 5 Sep 2012, Michael Wang wrote:
> 
>> Since the cachep and cachep->slabp_cache's l3 alien are in the same lock class,
>> fake report generated.
> 
> Ahh... That is a key insight into why this occurs.
> 
>> This should not happen since we already have init_lock_keys() which will
>> reassign the lock class for both l3 list and l3 alien.
> 
> Right. I was wondering why we still get intermitted reports on this.
> 
>> This patch will invoke init_lock_keys() after we done enable_cpucache()
>> instead of before to avoid the fake DEADLOCK report.
> 
> Acked-by: Christoph Lameter <cl@linux.com>

Thanks for your review.

And add Paul to the cc list(my skills on mailing is really poor...).

Regards,
Michael Wang

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Re: [PATCH] slab: fix the DEADLOCK issue on l3 alien lock

[Paul E. McKenney]

On Thu, Sep 06, 2012 at 11:05:11AM +0800, Michael Wang wrote:
> On 09/05/2012 09:55 PM, Christoph Lameter wrote:
> > On Wed, 5 Sep 2012, Michael Wang wrote:
> > 
> >> Since the cachep and cachep->slabp_cache's l3 alien are in the same lock class,
> >> fake report generated.
> > 
> > Ahh... That is a key insight into why this occurs.
> > 
> >> This should not happen since we already have init_lock_keys() which will
> >> reassign the lock class for both l3 list and l3 alien.
> > 
> > Right. I was wondering why we still get intermitted reports on this.
> > 
> >> This patch will invoke init_lock_keys() after we done enable_cpucache()
> >> instead of before to avoid the fake DEADLOCK report.
> > 
> > Acked-by: Christoph Lameter <cl@linux.com>
> 
> Thanks for your review.
> 
> And add Paul to the cc list(my skills on mailing is really poor...).

Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Re: [PATCH] slab: fix the DEADLOCK issue on l3 alien lock

[Pekka Enberg]

On Fri, Sep 7, 2012 at 1:29 AM, Paul E. McKenney
<paulmck@linux.vnet.ibm.com> wrote:
> On Thu, Sep 06, 2012 at 11:05:11AM +0800, Michael Wang wrote:
>> On 09/05/2012 09:55 PM, Christoph Lameter wrote:
>> > On Wed, 5 Sep 2012, Michael Wang wrote:
>> >
>> >> Since the cachep and cachep->slabp_cache's l3 alien are in the same lock class,
>> >> fake report generated.
>> >
>> > Ahh... That is a key insight into why this occurs.
>> >
>> >> This should not happen since we already have init_lock_keys() which will
>> >> reassign the lock class for both l3 list and l3 alien.
>> >
>> > Right. I was wondering why we still get intermitted reports on this.
>> >
>> >> This patch will invoke init_lock_keys() after we done enable_cpucache()
>> >> instead of before to avoid the fake DEADLOCK report.
>> >
>> > Acked-by: Christoph Lameter <cl@linux.com>
>>
>> Thanks for your review.
>>
>> And add Paul to the cc list(my skills on mailing is really poor...).
>
> Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

I'd also like to tag this for the stable tree to avoid bogus lockdep
reports. How far back in release history should we queue this?

Re: [PATCH] slab: fix the DEADLOCK issue on l3 alien lock

[Michael Wang]

On 09/08/2012 04:39 PM, Pekka Enberg wrote:
> On Fri, Sep 7, 2012 at 1:29 AM, Paul E. McKenney
> <paulmck@linux.vnet.ibm.com> wrote:
>> On Thu, Sep 06, 2012 at 11:05:11AM +0800, Michael Wang wrote:
>>> On 09/05/2012 09:55 PM, Christoph Lameter wrote:
>>>> On Wed, 5 Sep 2012, Michael Wang wrote:
>>>>
>>>>> Since the cachep and cachep->slabp_cache's l3 alien are in the same lock class,
>>>>> fake report generated.
>>>>
>>>> Ahh... That is a key insight into why this occurs.
>>>>
>>>>> This should not happen since we already have init_lock_keys() which will
>>>>> reassign the lock class for both l3 list and l3 alien.
>>>>
>>>> Right. I was wondering why we still get intermitted reports on this.
>>>>
>>>>> This patch will invoke init_lock_keys() after we done enable_cpucache()
>>>>> instead of before to avoid the fake DEADLOCK report.
>>>>
>>>> Acked-by: Christoph Lameter <cl@linux.com>
>>>
>>> Thanks for your review.
>>>
>>> And add Paul to the cc list(my skills on mailing is really poor...).
>>
>> Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> 
> I'd also like to tag this for the stable tree to avoid bogus lockdep
> reports. How far back in release history should we queue this?
Hi, Pekka

Sorry for the delayed reply, I try to find out the reason for commit
30765b92 but not get it yet, so I add Peter to the cc list.

The below patch for release 3.0.0 is the one to cause the bogus report.

commit 30765b92ada267c5395fc788623cb15233276f5c
Author: Peter Zijlstra <peterz@infradead.org>
Date:   Thu Jul 28 23:22:56 2011 +0200

    slab, lockdep: Annotate the locks before using them

    Fernando found we hit the regular OFF_SLAB 'recursion' before we
    annotate the locks, cure this.

    The relevant portion of the stack-trace:

    > [    0.000000]  [<c085e24f>] rt_spin_lock+0x50/0x56
    > [    0.000000]  [<c04fb406>] __cache_free+0x43/0xc3
    > [    0.000000]  [<c04fb23f>] kmem_cache_free+0x6c/0xdc
    > [    0.000000]  [<c04fb2fe>] slab_destroy+0x4f/0x53
    > [    0.000000]  [<c04fb396>] free_block+0x94/0xc1
    > [    0.000000]  [<c04fc551>] do_tune_cpucache+0x10b/0x2bb
    > [    0.000000]  [<c04fc8dc>] enable_cpucache+0x7b/0xa7
    > [    0.000000]  [<c0bd9d3c>] kmem_cache_init_late+0x1f/0x61
    > [    0.000000]  [<c0bba687>] start_kernel+0x24c/0x363
    > [    0.000000]  [<c0bba0ba>] i386_start_kernel+0xa9/0xaf

    Reported-by: Fernando Lopez-Lezcano <nando@ccrma.Stanford.EDU>
    Acked-by: Pekka Enberg <penberg@kernel.org>
    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Link: http://lkml.kernel.org/r/1311888176.2617.379.camel@laptop
    Signed-off-by: Ingo Molnar <mingo@elte.hu>

It moved init_lock_keys() before we build up the alien, so we failed to
reclass it.

Regards,
Michael Wang

> 

Re: [PATCH] slab: fix the DEADLOCK issue on l3 alien lock

[Pekka Enberg]

On Tue, Sep 11, 2012 at 5:50 AM, Michael Wang
<wangyun@linux.vnet.ibm.com> wrote:
> On 09/08/2012 04:39 PM, Pekka Enberg wrote:
>> On Fri, Sep 7, 2012 at 1:29 AM, Paul E. McKenney
>> <paulmck@linux.vnet.ibm.com> wrote:
>>> On Thu, Sep 06, 2012 at 11:05:11AM +0800, Michael Wang wrote:
>>>> On 09/05/2012 09:55 PM, Christoph Lameter wrote:
>>>>> On Wed, 5 Sep 2012, Michael Wang wrote:
>>>>>
>>>>>> Since the cachep and cachep->slabp_cache's l3 alien are in the same lock class,
>>>>>> fake report generated.
>>>>>
>>>>> Ahh... That is a key insight into why this occurs.
>>>>>
>>>>>> This should not happen since we already have init_lock_keys() which will
>>>>>> reassign the lock class for both l3 list and l3 alien.
>>>>>
>>>>> Right. I was wondering why we still get intermitted reports on this.
>>>>>
>>>>>> This patch will invoke init_lock_keys() after we done enable_cpucache()
>>>>>> instead of before to avoid the fake DEADLOCK report.
>>>>>
>>>>> Acked-by: Christoph Lameter <cl@linux.com>
>>>>
>>>> Thanks for your review.
>>>>
>>>> And add Paul to the cc list(my skills on mailing is really poor...).
>>>
>>> Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
>>
>> I'd also like to tag this for the stable tree to avoid bogus lockdep
>> reports. How far back in release history should we queue this?
> Hi, Pekka
>
> Sorry for the delayed reply, I try to find out the reason for commit
> 30765b92 but not get it yet, so I add Peter to the cc list.
>
> The below patch for release 3.0.0 is the one to cause the bogus report.
>
> commit 30765b92ada267c5395fc788623cb15233276f5c
> Author: Peter Zijlstra <peterz@infradead.org>
> Date:   Thu Jul 28 23:22:56 2011 +0200
>
>     slab, lockdep: Annotate the locks before using them
>
>     Fernando found we hit the regular OFF_SLAB 'recursion' before we
>     annotate the locks, cure this.
>
>     The relevant portion of the stack-trace:
>
>     > [    0.000000]  [<c085e24f>] rt_spin_lock+0x50/0x56
>     > [    0.000000]  [<c04fb406>] __cache_free+0x43/0xc3
>     > [    0.000000]  [<c04fb23f>] kmem_cache_free+0x6c/0xdc
>     > [    0.000000]  [<c04fb2fe>] slab_destroy+0x4f/0x53
>     > [    0.000000]  [<c04fb396>] free_block+0x94/0xc1
>     > [    0.000000]  [<c04fc551>] do_tune_cpucache+0x10b/0x2bb
>     > [    0.000000]  [<c04fc8dc>] enable_cpucache+0x7b/0xa7
>     > [    0.000000]  [<c0bd9d3c>] kmem_cache_init_late+0x1f/0x61
>     > [    0.000000]  [<c0bba687>] start_kernel+0x24c/0x363
>     > [    0.000000]  [<c0bba0ba>] i386_start_kernel+0xa9/0xaf
>
>     Reported-by: Fernando Lopez-Lezcano <nando@ccrma.Stanford.EDU>
>     Acked-by: Pekka Enberg <penberg@kernel.org>
>     Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
>     Link: http://lkml.kernel.org/r/1311888176.2617.379.camel@laptop
>     Signed-off-by: Ingo Molnar <mingo@elte.hu>
>
> It moved init_lock_keys() before we build up the alien, so we failed to
> reclass it.

I've queued the patch for v3.7. Thanks!