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

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Message-ID: <20070213150019.4b4d4827@localhost.localdomain>
Date:	Tue, 13 Feb 2007 15:00:19 +0000
From:	Alan <alan@...rguk.ukuu.org.uk>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	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>,
	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>,
	Davide Libenzi <davidel@...ilserver.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch 00/11] ANNOUNCE: "Syslets", generic asynchronous system
 call support

> A syslet is executed opportunistically: i.e. the syslet subsystem 
> assumes that the syslet will not block, and it will switch to a 
> cachemiss kernel thread from the scheduler. This means that even a 

How is scheduler fairness maintained ? and what is done for resource
accounting here ?

> that the kernel fills and user-space clears. Waiting is done via the 
> sys_async_wait() system call. Completion can be supressed on a per-atom 

They should be selectable as well iff possible.

> Open issues:

Let me add some more

	sys_setuid/gid/etc need to be synchronous only and not occur
while other async syscalls are running in parallel to meet current kernel
assumptions.

	sys_exec and other security boundaries must be synchronous only
and not allow async "spill over" (consider setuid async binary patching)

>  - sys_fork() and sys_async_exec() should be filtered out from the 
>    syscalls that are allowed - first one only makes sense with ptregs, 

clone and vfork. async_vfork is a real mindbender actually.

>    second one is a nice kernel recursion thing :) I didnt want to 
>    duplicate the sys_call_table though - maybe others have a better 
>    idea.

What are the semantics of async sys_async_wait and async sys_async ?

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