From 947ca1856a7e60aa6d20536785e6a42dff25aa6e Mon Sep 17 00:00:00 2001 From: Michael Wang Date: Wed, 5 Sep 2012 10:33:18 +0800 Subject: [PATCH] slab: fix the DEADLOCK issue on l3 alien lock 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 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] [] rt_spin_lock+0x50/0x56 > [ 0.000000] [] __cache_free+0x43/0xc3 > [ 0.000000] [] kmem_cache_free+0x6c/0xdc > [ 0.000000] [] slab_destroy+0x4f/0x53 > [ 0.000000] [] free_block+0x94/0xc1 > [ 0.000000] [] do_tune_cpucache+0x10b/0x2bb > [ 0.000000] [] enable_cpucache+0x7b/0xa7 > [ 0.000000] [] kmem_cache_init_late+0x1f/0x61 > [ 0.000000] [] start_kernel+0x24c/0x363 > [ 0.000000] [] i386_start_kernel+0xa9/0xaf Reported-by: Fernando Lopez-Lezcano Acked-by: Pekka Enberg Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/1311888176.2617.379.camel@laptop Signed-off-by: Ingo Molnar The commit moved init_lock_keys() before we build up the alien, so we failed to reclass it. Cc: # 3.0+ Acked-by: Christoph Lameter Tested-by: Paul E. McKenney Signed-off-by: Michael Wang Signed-off-by: Pekka Enberg --- mm/slab.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/slab.c b/mm/slab.c index 3b4587bb7b1..cd5a9265030 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; -- 2.43.2