linux-kernel - Re: [take24 0/6] kevent: Generic event handling mechanism.

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Date:	Fri, 24 Nov 2006 13:58:56 +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>,
	Alexander Viro <aviro@...hat.com>
Subject: Re: [take24 0/6] kevent: Generic event handling mechanism.

On Thu, Nov 23, 2006 at 12:34:50PM -0800, Ulrich Drepper (drepper@...hat.com) wrote:
> Evgeniy Polyakov wrote:
> >>>Btw, what about putting aditional multiplexer into add/remove/modify
> >>>switch? There will be logical 'ready' addon?
> >>Is it needed?  Usually this is done with a *_wait call with a timeout of 
> >>zero.  That code path might have to be optimized but it should already 
> >>be there.
> >
> >It does not allow to mark events as ready.
> >And current interfaces wake up when either timeout is zero (in this case
> >thread itself does not sleep and can process events), or when there is
> >_new_ work - since there is no _new_ work, when thread awakened to
> >process it was killed, kernel does not think that something is wrong.
> 
> Rather than mark an existing entry as ready, how about a call to inject 
> a new ready event?
> 
> This would be useful to implement functionality at userlevel and still 
> use an event queue to announce the availability.  Without this type of 
> functionality we'd need to use indirect notification via signal or pipe 
> or something like that.

With provided patch it is possible to wakeup 'for-free' - just call
kevent_ctl(ready) with zero number of ready events, so thread will be
awakened if it was in poll(kevent_fd), kevent_wait() or
kevent_get_events().

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

-- 
	Evgeniy Polyakov
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