linux-kernel - Re: init's children list is long and slows reaping children.

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: <461B4F76.1010807@garzik.org>
Date:	Tue, 10 Apr 2007 04:48:54 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Dave Jones <davej@...hat.com>, Robin Holt <holt@....com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Jack Steiner <steiner@...ricas.sgi.com>
Subject: Re: init's children list is long and slows reaping children.

Andrew Morton wrote:
> Well that obviously would be a dumb way to use keventd.  One would need
> to do schedule_work(), kick off the reset then do schedule_delayed_work()
> to wait (or poll) for its termination.

Far too complex.  See what Russell wrote, for instance.

When you are in a kernel thread, you can write more simple, 
straightforward, easy-to-debug code that does

	blah
	msleep()
	blah

rather than creating an insanely complicated state machine for the same 
thing.

ESPECIALLY if you are already inside a state machine (the case with 
libata PIO data xfer), you do not want to add another state machine 
inside of that.

A great many uses of kernel threads are to simplify device reset and 
polling in this way.  I know; a year ago I audited every kernel thread, 
because I was so frustrated with the per-CPU thread explosion.

Thus, rather than forcing authors to make their code more complex, we 
should find another solution.

	Jeff

-
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/