linux-kernel - Re: [patch 00/13] Syslets, "Threadlets", generic AIO support, v3

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Message-ID: <20070228202156.GA15846@elte.hu>
Date:	Wed, 28 Feb 2007 21:21:56 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Davide Libenzi <davidel@...ilserver.org>
Cc:	Ulrich Drepper <drepper@...hat.com>,
	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>,
	Zach Brown <zach.brown@...cle.com>,
	Evgeniy Polyakov <johnpol@....mipt.ru>,
	"David S. Miller" <davem@...emloft.net>,
	Suparna Bhattacharya <suparna@...ibm.com>,
	Jens Axboe <jens.axboe@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch 00/13] Syslets, "Threadlets", generic AIO support, v3

* Davide Libenzi <davidel@...ilserver.org> wrote:

> My point is, the syslet infrastructure is expensive for the kernel in 
> terms of compat, [...]

it is not. Today i've implemented 64-bit syslets on x86_64 and 
32-bit-on-64-bit compat syslets. Both the 64-bit and the 32-bit syslet 
(and threadlet) binaries work just fine on a 64-bit kernel, and they 
share 99% of the infrastructure. There's only a single #ifdef 
CONFIG_COMPAT in kernel/async.c:

#ifdef CONFIG_COMPAT

asmlinkage struct syslet_uatom __user *
compat_sys_async_exec(struct syslet_uatom __user *uatom,
                      struct async_head_user __user *ahu)
{
        return __sys_async_exec(uatom, ahu, &compat_sys_call_table,
                                compat_NR_syscalls);
}

#endif

Even mixed-mode syslets should work (although i havent specifically 
tested them), where the head switches between 64-bit and 32-bit mode and 
submits syslets from both 64-bit and from 32-bit mode, and at the same 
time there might be both 64-bit and 32-bit syslets 'in flight'.

But i'm happy to change the syslet API in any sane way, and did so based 
on feedback from Jens who is actually using them.

	Ingo
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