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    Subject[PATCH v7 04/23] locking/lockdep: Avoid that add_chain_cache() adds an invalid chain to the cache
    Date
    Make sure that add_chain_cache() returns 0 and does not modify the
    chain hash if nr_chain_hlocks == MAX_LOCKDEP_CHAIN_HLOCKS before this
    function is called.

    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Waiman Long <longman@redhat.com>
    Cc: Johannes Berg <johannes@sipsolutions.net>
    Signed-off-by: Bart Van Assche <bvanassche@acm.org>
    ---
    kernel/locking/lockdep.c | 11 +----------
    1 file changed, 1 insertion(+), 10 deletions(-)

    diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
    index b00c6edd6a28..404086b23fc7 100644
    --- a/kernel/locking/lockdep.c
    +++ b/kernel/locking/lockdep.c
    @@ -2206,16 +2206,8 @@ static inline int add_chain_cache(struct task_struct *curr,
    chain_hlocks[chain->base + j] = lock_id;
    }
    chain_hlocks[chain->base + j] = class - lock_classes;
    - }
    -
    - if (nr_chain_hlocks < MAX_LOCKDEP_CHAIN_HLOCKS)
    nr_chain_hlocks += chain->depth;
    -
    -#ifdef CONFIG_DEBUG_LOCKDEP
    - /*
    - * Important for check_no_collision().
    - */
    - if (unlikely(nr_chain_hlocks > MAX_LOCKDEP_CHAIN_HLOCKS)) {
    + } else {
    if (!debug_locks_off_graph_unlock())
    return 0;

    @@ -2223,7 +2215,6 @@ static inline int add_chain_cache(struct task_struct *curr,
    dump_stack();
    return 0;
    }
    -#endif

    hlist_add_head_rcu(&chain->entry, hash_head);
    debug_atomic_inc(chain_lookup_misses);
    --
    2.21.0.rc0.258.g878e2cd30e-goog
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