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Date: Tue, 19 Dec 2000 02:32:40 +0100
From: Jamie Lokier <lk@tantalophile.demon.co.uk>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: Petr Vandrovec <vandrove@vc.cvut.cz>, linux-kernel@vger.kernel.org
Subject: Re: 2.4.0-test13-pre1 lockup: run_task_queue or tty_io are wrong
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In-Reply-To: <Pine.LNX.4.10.10012181556220.4466-100000@penguin.transmeta.com>; from torvalds@transmeta.com on Mon, Dec 18, 2000 at 03:58:08PM -0800
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Linus Torvalds wrote:
> > I wasn't clear.  The sentinel is a local structure on the stack, and
> > only exists while run_task_queue is executing.  Another name for this is
> > "deletion-safe pointer".
> 
> Yes, except run_task_queue removes every object it finds. So two
> concurrent run_task_queues would be bad.

That could work, but forget it.  I've just looked at Andrew's patch and
it's much nicer :-)

If you put a spinlock around the list operations in Andrew's version,
you'd have safe tqueue deletions again (if you felt that was worth
having).  Some tricks and you can make it a different spinlock, but I
doubt that would be a net benefit.

-- Jamie
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