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    Subject[PATCH v11 1/3] lockdep: use this_cpu_ptr instead of get_cpu_var stats
    Date
    From: "Joel Fernandes (Google)" <joel@joelfernandes.org>

    get_cpu_var disables preemption which has the potential to call into the
    preemption disable trace points causing some complications. There's also
    no need to disable preemption in uses of get_lock_stats anyway since
    preempt is already disabled. So lets simplify the code.

    Suggested-by: Peter Zijlstra <peterz@infradead.org>
    Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
    ---
    kernel/locking/lockdep.c | 10 +---------
    1 file changed, 1 insertion(+), 9 deletions(-)

    diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
    index 5fa4d3138bf1..8f5ce0048d15 100644
    --- a/kernel/locking/lockdep.c
    +++ b/kernel/locking/lockdep.c
    @@ -248,12 +248,7 @@ void clear_lock_stats(struct lock_class *class)

    static struct lock_class_stats *get_lock_stats(struct lock_class *class)
    {
    - return &get_cpu_var(cpu_lock_stats)[class - lock_classes];
    -}
    -
    -static void put_lock_stats(struct lock_class_stats *stats)
    -{
    - put_cpu_var(cpu_lock_stats);
    + return &this_cpu_ptr(&cpu_lock_stats)[class - lock_classes];
    }

    static void lock_release_holdtime(struct held_lock *hlock)
    @@ -271,7 +266,6 @@ static void lock_release_holdtime(struct held_lock *hlock)
    lock_time_inc(&stats->read_holdtime, holdtime);
    else
    lock_time_inc(&stats->write_holdtime, holdtime);
    - put_lock_stats(stats);
    }
    #else
    static inline void lock_release_holdtime(struct held_lock *hlock)
    @@ -4090,7 +4084,6 @@ __lock_contended(struct lockdep_map *lock, unsigned long ip)
    stats->contending_point[contending_point]++;
    if (lock->cpu != smp_processor_id())
    stats->bounces[bounce_contended + !!hlock->read]++;
    - put_lock_stats(stats);
    }

    static void
    @@ -4138,7 +4131,6 @@ __lock_acquired(struct lockdep_map *lock, unsigned long ip)
    }
    if (lock->cpu != cpu)
    stats->bounces[bounce_acquired + !!hlock->read]++;
    - put_lock_stats(stats);

    lock->cpu = cpu;
    lock->ip = ip;
    --
    2.18.0.345.g5c9ce644c3-goog
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