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Date: Thu, 21 Dec 2000 21:38:43 +1100
From: Andrew Morton <andrewm@uow.edu.au>
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To: Andrea Arcangeli <andrea@suse.de>
CC: Alan Cox <alan@lxorguk.ukuu.org.uk>, linux-kernel@vger.kernel.org
Subject: Re: Linux 2.2.19pre2
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Andrea Arcangeli wrote:
> 
> The fact you could mix non-exclusive and exlusive wakeups in the same waitqueue
> was a feature not a misfeature. Then of course you cannot register in two
> waitqueues one with wake-one and one with wake-all but who does that anyways?
> Definitely not an issue for 2.2.x.

Definitely?  Let's think about that.

> I think the real reason for spearating the two things as davem proposed is
> because otherwise we cannot register for a LIFO wake-one in O(1) as we needed
> for accept.

Yes.  In other words, if we try to do O(1) LIFO, we can cause lost wakeups.

> Other thing about your patch, adding TASK_EXCLUSIVE to
> wake_up/wake_up_interruptible is useless.

This enables wake_up_all().



Anyway, this is all just noise.

The key question is: which of the following do we want?

a) A simple, specific accept()-accelerator, and 2.2 remains without
   an exclusive wq API or

b) A general purpose exclusive wq mechanism which does not correctly
   support waiting on two queues simultaneuously where one is
   exclusive or

c) A general purpose exclusive wq mechanism which _does_ support it.

Each choice has merit!  You seem to want b).  davem wants c).

And given that 2.2 has maybe 2-4 years life left in it, I'd
agree with David.  Let's do it once and do it right while the issue
is fresh in our minds.

Yes?

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