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    Subject[PATCH] lockdep: Fix redundant_hardirqs_on incremented with irqs enabled
    Date
    When a path restore the flags while irqs are already enabled, we
    update the per cpu var redundant_hardirqs_on in a racy fashion
    and debug_atomic_inc() warns about this situation.

    In this particular case, we need to explictly disable the irqs before
    updating this stat var in order to update it safely.

    Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
    Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: David Miller <davem@davemloft.net>
    Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    ---
    kernel/lockdep.c | 4 ++++
    1 files changed, 4 insertions(+), 0 deletions(-)

    diff --git a/kernel/lockdep.c b/kernel/lockdep.c
    index 78325f8..65d4336 100644
    --- a/kernel/lockdep.c
    +++ b/kernel/lockdep.c
    @@ -2298,7 +2298,11 @@ void trace_hardirqs_on_caller(unsigned long ip)
    return;

    if (unlikely(curr->hardirqs_enabled)) {
    + unsigned long flags;
    +
    + raw_local_irq_save(flags);
    debug_atomic_inc(redundant_hardirqs_on);
    + raw_local_irq_restore(flags);
    return;
    }
    /* we'll do an OFF -> ON transition: */
    --
    1.6.2.3


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