linux-kernel - Re: [RFC -v2 PATCH 2/3] sched: add yield

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: <4D0F78DF.9010908@redhat.com>
Date:	Mon, 20 Dec 2010 10:40:15 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Mike Galbraith <mgalbraith@...e.de>
CC:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Avi Kiviti <avi@...hat.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Chris Wright <chrisw@...s-sol.org>
Subject: Re: [RFC -v2 PATCH 2/3] sched: add yield_to function

On 12/17/2010 02:15 AM, Mike Galbraith wrote:

> BTW, with this vruntime donation thingy, what prevents a task from
> forking off accomplices who do nothing but wait for a wakeup and
> yield_to(exploit)?
>
> Even swapping vruntimes in the same cfs_rq is dangerous as hell, because
> one party is going backward.

I just realized the answer to this question.

We only give cpu time to tasks that are runnable, but not
currently running.  That ensures one task cannot block others
from running by having time yielded to it constantly.
--
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/