linux-kernel - Re: [take25 1/6] kevent: Description.

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Date:	Fri, 24 Nov 2006 14:01:44 +0300
From:	Evgeniy Polyakov <johnpol@....mipt.ru>
To:	Ulrich Drepper <drepper@...hat.com>
Cc:	David Miller <davem@...emloft.net>, Andrew Morton <akpm@...l.org>,
	netdev <netdev@...r.kernel.org>,
	Zach Brown <zach.brown@...cle.com>,
	Christoph Hellwig <hch@...radead.org>,
	Chase Venters <chase.venters@...entec.com>,
	Johann Borck <johann.borck@...sedata.com>,
	linux-kernel@...r.kernel.org, Jeff Garzik <jeff@...zik.org>
Subject: Re: [take25 1/6] kevent: Description.

On Thu, Nov 23, 2006 at 11:45:36AM -0800, Ulrich Drepper (drepper@...hat.com) wrote:
> Evgeniy Polyakov wrote:
> >Kernel does not put there a new entry, it is only done inside
> >kevent_wait(). Entries are put into queue (in any context), where they can 
> >be obtained
> >from only kevent_wait() or kevent_get_events().
> 
> I know this is how it's done now.  But it is not where it has to end. 
> IMO we have to get to a solution where new events are posted to the ring 
> buffer asynchronously, i.e., without a thread calling kevent_wait.  And 
> then you need the extra parameter and verification.  Even if it's today 
> not needed we have to future-proof the interface since it cannot be 
> changed once in use.

There is a special flag in kevent_user to wake it if there are no ready
events - kernel thread which has added new events will set it and thus
subsequent kevent_wait() will return with updated indexes - userspace
must check indexes after kevent_wait().

> -- 
> ➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, 
> CA ❖

-- 
	Evgeniy Polyakov
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