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    SubjectRe: [ 004/120] slab: fix the DEADLOCK issue on l3 alien lock
    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;
    >
    >
    >
    > --
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