linux-kernel - Re: [1/1] Block device throttling [Re: Distributed storage.]

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: <200708271457.38100.phillips@phunq.net>
Date:	Mon, 27 Aug 2007 14:57:37 -0700
From:	Daniel Phillips <phillips@...nq.net>
To:	Evgeniy Polyakov <johnpol@....mipt.ru>
Cc:	Jens Axboe <jens.axboe@...cle.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [1/1] Block device throttling [Re: Distributed storage.]

Say Evgeniy, something I was curious about but forgot to ask you 
earlier...

On Wednesday 08 August 2007 03:17, Evgeniy Polyakov wrote:
> ...All oerations are not atomic, since we do not care about precise
> number of bios, but a fact, that we are close or close enough to the
> limit. 
> ... in bio->endio
> +			q->bio_queued--;

In your proposed patch, what prevents the race:

			cpu1						cpu2

	read q->bio_queued
									q->bio_queued--
	write q->bio_queued - 1
	Whoops! We leaked a throttle count.

Regards,

Daniel
-
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/