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To: Andi Kleen <andi@firstfloor.org>
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From: ebiederm@xmission.com (Eric W. Biederman)
Date: Mon, 07 Dec 2009 15:19:59 -0800
In-Reply-To: <87ws0y76q7.fsf@basil.nowhere.org> (Andi Kleen's message of "Mon\, 07 Dec 2009 23\:35\:28 +0100")
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Subject: Re: [rfc] "fair" rw spinlocks
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Andi Kleen <andi@firstfloor.org> writes:

> ebiederm@xmission.com (Eric W. Biederman) writes:
>
>> "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> writes:
>>>
>>> Is it required that all of the processes see the signal before the
>>> corresponding interrupt handler returns?  (My guess is "no", which
>>> enables a trick or two, but thought I should ask.)
>>
>> Not that I recall.  I think it is just an I/O completed signal.
>
> Wasn't there the sysrq SAK too? That one definitely would need
> to be careful about synchronicity.

SAK from sysrq is done through schedule work, I seem to recall the
locking being impossible otherwise.  There is also send_sig_all and a
few others from sysrq.  I expect we could legitimately make them
schedule_work as well if needed.

Eric