This is a note to let you know that I've just added the patch titled
slab: fix the DEADLOCK issue on l3 alien lock
to the 3.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
slab-fix-the-deadlock-issue-on-l3-alien-lock.patch
and it can be found in the queue-3.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 947ca1856a7e60aa6d20536785e6a42dff25aa6e Mon Sep 17 00:00:00 2001
From: Michael Wang <[email protected]>
Date: Wed, 5 Sep 2012 10:33:18 +0800
Subject: slab: fix the DEADLOCK issue on l3 alien lock
From: Michael Wang <[email protected]>
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:
commit 30765b92ada267c5395fc788623cb15233276f5c
Author: Peter Zijlstra <[email protected]>
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 <[email protected]>
Acked-by: Pekka Enberg <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/1311888176.2617.379.camel@laptop
Signed-off-by: Ingo Molnar <[email protected]>
The commit moved init_lock_keys() before we build up the alien, so we
failed to reclass it.
Acked-by: Christoph Lameter <[email protected]>
Tested-by: Paul E. McKenney <[email protected]>
Signed-off-by: Michael Wang <[email protected]>
Signed-off-by: Pekka Enberg <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
diff --git a/mm/slab.c b/mm/slab.c
index 3b4587b..cd5a926 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1774,9 +1774,6 @@ 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)
@@ -1784,6 +1781,9 @@ 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;
Patches currently in stable-queue which might be from
[email protected] are
queue-3.0/slab-fix-the-deadlock-issue-on-l3-alien-lock.patch
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