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    George Anzinger wrote:
    > The notion of releasing a spin lock by initializing it seems IMHO, on
    > the face of it, way off. Firstly the protected area is no longer
    > protected which could lead to undefined errors/ crashes and secondly,
    > any future use of spinlocks to control preemption could have a lot of
    > trouble with this, principally because the locker is unknown.
    > In the case at hand, it would seem that an unlocked path to the console
    > is a more correct answer that gives the system a far better chance of
    > actually remaining viable.

    Does bust_spinlocks() muck up the preemptive kernel's spinlock
    counting? Would you prefer spin_trylock()/spin_unlock()?
    It doesn't matter - if we call bust_spinlocks() the kernel is
    known to be dead meat and there is a fsck in your near future.

    We are still trying to find out why kumon@fujitsu's 8-way is
    crashing on the test10-pre5 sched.c. Looks like it's fixed
    in test11-pre2 but we want to know _why_ it's fixed. And at
    present each time he hits the bug, his printk() deadlocks.

    So bust_spinlocks() is a RAS feature :) A very important one -
    it's terrible when your one-in-a-trillion bug happens and there
    are no diagnostics.

    It's a work-in-progress. There are a lot of things which
    can cause printk to deadlock:

    - console_lock
    - timerlist_lock
    - global_irq_lock (console code does global_cli)
    - log_wait.lock
    - tasklist_lock (printk does wake_up) (*)
    - runqueue_lock (printk does wake_up)

    I'll be proposing a better patch for this in a few days.

    (*) Keith: this explains why you can't do a printk() in
    __wake_up_common: printk calls wake_up(). Duh.
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