Linux-kernel mailing list archive 1999-37,: Re: spin_lock and linux philosophy question...

# Re: spin_lock and linux philosophy question...

Benjamin LaHaise (kernel@kvack.org)
Mon, 13 Sep 1999 10:43:54 -0400 (EDT)

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On Mon, 13 Sep 1999, Robert Dinse wrote:

> On Mon, 13 Sep 1999, Momchil Velikov wrote:
> >
> > You can also use a spinlock in an interrupt handler, where you can't sleep at
> > all.
> >
> > Regards,
> > -velco
>
> Are there ever cases where you lock outside of interrupts but expect code
> inside of an interrupt handler to unlock? Or conversely, cases where you lock
> during an interrupt, do some preliminary work, then return expecting code
> outside to unlock?

Not with spinlocks. Which is to say that:

a) a process may never block while holding a spinlock
b) an interrupt context may never end while still holding a
spinlock

I'm not too sure what the debugging spinlock code does wrt these
invariants, but checking a local lock depth wouldn't be too difficult.

-ben

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