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    Subject[tip:irq/core] genirq: Remove paranoid warnons and bogus fixups
    Commit-ID:  e04268b0effc0ceea366c50b3107baad9edadafa
    Gitweb: http://git.kernel.org/tip/e04268b0effc0ceea366c50b3107baad9edadafa
    Author: Thomas Gleixner <tglx@linutronix.de>
    AuthorDate: Thu, 15 Mar 2012 22:55:21 +0100
    Committer: Thomas Gleixner <tglx@linutronix.de>
    CommitDate: Fri, 16 Mar 2012 11:27:28 +0100

    genirq: Remove paranoid warnons and bogus fixups

    Alexander pointed out that the warnons in the regular exit path are
    bogus and the thread_mask one actually could be triggered when
    __setup_irq() hands out that thread_mask again after __free_irq()
    dropped irq_desc->lock.

    Thinking more about it, neither IRQTF_RUNTHREAD nor the bit in
    thread_mask can be set as this is the regular exit path. We come here
    due to:
    __free_irq()
    remove action from desc
    synchronize_irq()
    kthread_stop()

    So synchronize_irq() makes sure that the thread finished running and
    cleaned up both the thread_active count and thread_mask. After that
    point nothing can set IRQTF_RUNTHREAD on this action. So the warnons
    and the cleanups are pointless.

    Reported-by: Alexander Gordeev <agordeev@redhat.com>
    Cc: Ido Yariv <ido@wizery.com>
    Link: http://lkml.kernel.org/r/20120315190755.GA6732@dhcp-26-207.brq.redhat.com
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    ---
    kernel/irq/manage.c | 14 ++++----------
    1 files changed, 4 insertions(+), 10 deletions(-)

    diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
    index 453feed..b0ccd1a 100644
    --- a/kernel/irq/manage.c
    +++ b/kernel/irq/manage.c
    @@ -804,17 +804,11 @@ static int irq_thread(void *data)
    * This is the regular exit path. __free_irq() is stopping the
    * thread via kthread_stop() after calling
    * synchronize_irq(). So neither IRQTF_RUNTHREAD nor the
    - * oneshot mask bit should be set.
    + * oneshot mask bit can be set. We cannot verify that as we
    + * cannot touch the oneshot mask at this point anymore as
    + * __setup_irq() might have given out currents thread_mask
    + * again.
    *
    - * Verify that this is true.
    - */
    - if (WARN_ON(test_and_clear_bit(IRQTF_RUNTHREAD, &action->thread_flags)))
    - wake_threads_waitq(desc);
    -
    - if (WARN_ON(desc->threads_oneshot & action->thread_mask))
    - irq_finalize_oneshot(desc, action, true);
    -
    - /*
    * Clear irq_thread. Otherwise exit_irq_thread() would make
    * fuzz about an active irq thread going into nirvana.
    */

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