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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20070213221810.GF22104@elte.hu>
Date:	Tue, 13 Feb 2007 23:18:10 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Evgeniy Polyakov <johnpol@....mipt.ru>
Cc:	Benjamin LaHaise <bcrl@...ck.org>, Alan <alan@...rguk.ukuu.org.uk>,
	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>,
	"David S. Miller" <davem@...emloft.net>,
	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

* Evgeniy Polyakov <johnpol@....mipt.ru> wrote:

> [...] it still has a problem - syscall blocks and the same thread thus 
> is not allowed to continue execution and fill the pipe - so what if 
> system issues thousands of requests and there are only tens of working 
> thread at most. [...]

the same thread is allowed to continue execution even if the system call 
blocks: take a look at async_schedule(). The blocked system-call is 'put 
aside' (in a sleeping thread), the kernel switches the user-space 
context (registers) to a free kernel thread and switches to it - and 
returns to user-space as if nothing happened - allowing the user-space 
context to 'fill the pipe' as much as it can. Or did i misunderstand 
your point?

basically there's SYSLET_ASYNC for 'always async' and SYSLET_SYNC for 
'always sync' - but the default syslet behavior is: 'try sync and switch 
transparently to async on demand'. The testcode i sent very much uses 
this. (and this mechanism is in essence Zach's fibril-switching thing, 
but done via kernel threads.)

	Ingo
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/