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SubjectRe: mutex_unlock() in interrupt context
On Fri, 13 Jul 2007 19:14:56 -0500 Jerry Cooperstein <jerry.cooperstein@charter.net> wrote:

> kernel/mutex.c says about mutex_unlock():
>
> * This function must not be used in interrupt context.
>
> However I have done some simple test cases that show
> it works without complaint. Now I understand that one
> shouldn't do this for good reasons. So is this a
> good coding practice rule, but something that
> could appear in sloppy or poorly designed code?
>

mutex_unlock() must be called by the process which did the mutex_lock().
Doing the mutex_unlock() from an interrupt will cause warnings when run
with debugging enabled. You should run with debugging enabled when doing
any development.

Also, mutex_unlock() takes a mutex-internal spinlock in a non-irq-safe
fashion - if the timing is right, your mutex_unlock() in IRQ context will
deadlock.

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