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    Subject[patch 05/71] fix RCU-callback-after-kmem_cache_destroy problem in sl[aou]b
    2.6.30-stable review patch.  If anyone has any objections, please let us know.

    ------------------

    From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

    commit 7ed9f7e5db58c6e8c2b4b738a75d5dcd8e17aad5 upstream.

    Jesper noted that kmem_cache_destroy() invokes synchronize_rcu() rather than
    rcu_barrier() in the SLAB_DESTROY_BY_RCU case, which could result in RCU
    callbacks accessing a kmem_cache after it had been destroyed.

    Acked-by: Matt Mackall <mpm@selenic.com>
    Reported-by: Jesper Dangaard Brouer <hawk@comx.dk>
    Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    mm/slab.c | 2 +-
    mm/slob.c | 2 ++
    mm/slub.c | 2 ++
    3 files changed, 5 insertions(+), 1 deletion(-)

    --- a/mm/slab.c
    +++ b/mm/slab.c
    @@ -2592,7 +2592,7 @@ void kmem_cache_destroy(struct kmem_cach
    }

    if (unlikely(cachep->flags & SLAB_DESTROY_BY_RCU))
    - synchronize_rcu();
    + rcu_barrier();

    __kmem_cache_destroy(cachep);
    mutex_unlock(&cache_chain_mutex);
    --- a/mm/slob.c
    +++ b/mm/slob.c
    @@ -590,6 +590,8 @@ EXPORT_SYMBOL(kmem_cache_create);

    void kmem_cache_destroy(struct kmem_cache *c)
    {
    + if (c->flags & SLAB_DESTROY_BY_RCU)
    + rcu_barrier();
    slob_free(c, sizeof(struct kmem_cache));
    }
    EXPORT_SYMBOL(kmem_cache_destroy);
    --- a/mm/slub.c
    +++ b/mm/slub.c
    @@ -2490,6 +2490,8 @@ static inline int kmem_cache_close(struc
    */
    void kmem_cache_destroy(struct kmem_cache *s)
    {
    + if (s->flags & SLAB_DESTROY_BY_RCU)
    + rcu_barrier();
    down_write(&slub_lock);
    s->refcount--;
    if (!s->refcount) {



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