linux-kernel - Re: [RFC -v3 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: <1294161737.2016.177.camel@laptop>
Date:	Tue, 04 Jan 2011 18:22:17 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Hillf Danton <dhillf@...il.com>
Cc:	Rik van Riel <riel@...hat.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Avi Kiviti <avi@...hat.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Mike Galbraith <efault@....de>,
	Chris Wright <chrisw@...s-sol.org>
Subject: Re: [RFC -v3 PATCH 2/3] sched: add yield_to function

On Wed, 2011-01-05 at 01:12 +0800, Hillf Danton wrote:
> On Wed, Jan 5, 2011 at 1:08 AM, Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
> > On Wed, 2011-01-05 at 00:51 +0800, Hillf Danton wrote:
> >> Where is the yield_to callback in the patch for RT schedule class?
> >> If @p is RT, what could you do?
> >
> > RT guests are a pipe dream, you first need to get the hypervisor (kvm in
> > this case) to be RT, which it isn't. Then you either need to very
> > statically set-up the host and the guest scheduling constraints (not
> > possible with RR/FIFO) or have a complete paravirt RT scheduler which
> > communicates its requirements to the host.
> >
> Even guest is not RT, you could not prevent it from being preempted by
> RT task which has nothing to do guests.

Sure, but yield_to() being a NOP for RT tasks is perfectly fine. Pretty
much all yield*() usage is a bug anyway.
--
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/