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    Subjectproblem in md?
    Hi Ingo,
    IIRC I suspected a possible problem in md_thread() a few weeks ago, and
    I proved wrong. But now I'm sure that there could be a problem!

    md_thread calls

    for(;;) {

    are you aware that do_something() is called WITHOUT the global interrupt
    lock held?

    Let me explain it:
    * the initial cli() disables the local interrupts, and acquires the
    global lock.
    * interruptible_sleep_on() calls spin_lock_irqsave(), and this saves the
    _local_ interrupt flag on the stack.
    * schedule() releases the global interrupt lock.
    * schedule() eventually returns, and interruptible_sleep_on() restores
    the _local_ interrupt flag. (hidden in wq_write_unlock_irqrestore().)
    * __global_cli() notices that the local interrupts are disabled, and
    downgrades the global lock to a local lock.

    I think you should add an sti() just before the cli(). You cannot call
    the sti() before interruptible_sleep_on(), this could cause a race.

    Please correct me if I'm wrong,


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