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    Subject[PATCH v1 16/25] netfilter: nft_set_rbtree: Use sequence counter with associated rwlock
    Date
    A sequence counter write side critical section must be protected by some
    form of locking to serialize writers. A plain seqcount_t does not
    contain the information of which lock must be held when entering a write
    side critical section.

    Use the new seqcount_rwlock_t data type, which allows to associate a
    rwlock with the sequence counter. This enables lockdep to verify that
    the rwlock used for writer serialization is held when the write side
    critical section is entered.

    If lockdep is disabled this lock association is compiled out and has
    neither storage size nor runtime overhead.

    Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
    ---
    net/netfilter/nft_set_rbtree.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/net/netfilter/nft_set_rbtree.c b/net/netfilter/nft_set_rbtree.c
    index 3ffef454d469..f50d986d43c5 100644
    --- a/net/netfilter/nft_set_rbtree.c
    +++ b/net/netfilter/nft_set_rbtree.c
    @@ -18,7 +18,7 @@
    struct nft_rbtree {
    struct rb_root root;
    rwlock_t lock;
    - seqcount_t count;
    + seqcount_rwlock_t count;
    struct delayed_work gc_work;
    };

    @@ -505,7 +505,7 @@ static int nft_rbtree_init(const struct nft_set *set,
    struct nft_rbtree *priv = nft_set_priv(set);

    rwlock_init(&priv->lock);
    - seqcount_init(&priv->count);
    + seqcount_rwlock_init(&priv->count, &priv->lock);
    priv->root = RB_ROOT;

    INIT_DEFERRABLE_WORK(&priv->gc_work, nft_rbtree_gc);
    --
    2.20.1
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