linux-kernel - Re: [patch 00/11] ANNOUNCE: "Syslets", generic asynchronous system call support

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Date:	Tue, 13 Feb 2007 20:49:23 -0800 (PST)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Ingo Molnar <mingo@...e.hu>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@....com.au>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Ulrich Drepper <drepper@...hat.com>,
	Zach Brown <zach.brown@...cle.com>,
	Evgeniy Polyakov <johnpol@....mipt.ru>,
	"David S. Miller" <davem@...emloft.net>,
	Benjamin LaHaise <bcrl@...ck.org>,
	Suparna Bhattacharya <suparna@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch 00/11] ANNOUNCE: "Syslets", generic asynchronous system
 call support

On Tue, 13 Feb 2007, Davide Libenzi wrote:

[...]

> So the sys_async_exec task is going to block. Now, am I being really 
> tired, or the cachemiss fast return is simply not there?

The former 8)

pick_new_async_head()
	new_task->ah = ah;

cachemiss_loop()
	for (;;) {
		if (unlikely(t->ah || ...))
			break;


> There's another problem AFAICS:
> 
> - We woke up one of the cachemiss_loop threads in pick_new_async_thread
> 
> - The threads wakes up, mark itself as busy, and look at the ->work 
>   pointer hoping to find something to work on
> 
> But we never set that pointer to a userspace atom AFAICS. Me blind? :)

I still don't see at->work ever set to a valid userspace atom though...



- Davide


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