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    Subject[PATCH 5.4 051/214] locking/lockdep: Fix overflow in presentation of average lock-time
    Date
    From: Chris Wilson <chris@chris-wilson.co.uk>

    [ Upstream commit a7ef9b28aa8d72a1656fa6f0a01bbd1493886317 ]

    Though the number of lock-acquisitions is tracked as unsigned long, this
    is passed as the divisor to div_s64() which interprets it as a s32,
    giving nonsense values with more than 2 billion acquisitons. E.g.

    acquisitions holdtime-min holdtime-max holdtime-total holdtime-avg
    -------------------------------------------------------------------------
    2350439395 0.07 353.38 649647067.36 0.-32

    Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Link: https://lore.kernel.org/r/20200725185110.11588-1-chris@chris-wilson.co.uk
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    kernel/locking/lockdep_proc.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/kernel/locking/lockdep_proc.c b/kernel/locking/lockdep_proc.c
    index 9bb6d2497b040..581f818181386 100644
    --- a/kernel/locking/lockdep_proc.c
    +++ b/kernel/locking/lockdep_proc.c
    @@ -400,7 +400,7 @@ static void seq_lock_time(struct seq_file *m, struct lock_time *lt)
    seq_time(m, lt->min);
    seq_time(m, lt->max);
    seq_time(m, lt->total);
    - seq_time(m, lt->nr ? div_s64(lt->total, lt->nr) : 0);
    + seq_time(m, lt->nr ? div64_u64(lt->total, lt->nr) : 0);
    }

    static void seq_stats(struct seq_file *m, struct lock_stat_data *data)
    --
    2.25.1


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