Re: [ 004/120] slab: fix the DEADLOCK issue on l3 alien lock

Steven Rostedt
2012-10-18T13:20:25Z

On Thu, Oct 11, 2012 at 09:59:16AM +0900, Greg Kroah-Hartman wrote:
> 3.4-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Michael Wang <wangyun@linux.vnet.ibm.com>
>
> commit 947ca1856a7e60aa6d20536785e6a42dff25aa6e upstream.
>
> 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.
>
> Michael traced the problem back to a commit in release 3.0.0:

I don't see this fix in the last 3.0 stable release. Shouldn't it go
there too?

-- Steve

>
> 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>
>
> The commit moved init_lock_keys() before we build up the alien, so we
> failed to reclass it.
>
> Acked-by: Christoph Lameter <cl@linux.com>
> Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
> Signed-off-by: Pekka Enberg <penberg@kernel.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
> ---
> mm/slab.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -1685,9 +1685,6 @@ void __init kmem_cache_init_late(void)
>
> g_cpucache_up = LATE;
>
> - /* Annotate slab for lockdep -- annotate the malloc caches */
> - init_lock_keys();
> -
> /* 6) resize the head arrays to their final sizes */
> mutex_lock(&cache_chain_mutex);
> list_for_each_entry(cachep, &cache_chain, next)
> @@ -1695,6 +1692,9 @@ void __init kmem_cache_init_late(void)
> BUG();
> mutex_unlock(&cache_chain_mutex);
>
> + /* Annotate slab for lockdep -- annotate the malloc caches */
> + init_lock_keys();
> +
> /* Done! */
> g_cpucache_up = FULL;
>
>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/