linux-kernel - Re: [rfc] "fair" rw spinlocks

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Message-ID: <m1fx7m1ie8.fsf@fess.ebiederm.org>
Date:	Mon, 07 Dec 2009 15:19:59 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Andi Kleen <andi@...stfloor.org>
Cc:	paulmck@...ux.vnet.ibm.com,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Christoph Hellwig <hch@...radead.org>,
	Nick Piggin <npiggin@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [rfc] "fair" rw spinlocks

Andi Kleen <andi@...stfloor.org> writes:

> ebiederm@...ssion.com (Eric W. Biederman) writes:
>
>> "Paul E. McKenney" <paulmck@...ux.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
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