linux-kernel - Re: [PATCH v2 10/12] Maintain preemptability count even for !CONFIG

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]

Date:	Mon, 23 Nov 2009 16:34:15 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Gleb Natapov <gleb@...hat.com>
Cc:	kvm@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, avi@...hat.com, mingo@...e.hu,
	tglx@...utronix.de, hpa@...or.com, riel@...hat.com
Subject: Re: [PATCH v2 10/12] Maintain preemptability count even for
 !CONFIG_PREEMPT kernels

On Mon, 2009-11-23 at 16:06 +0200, Gleb Natapov wrote:
> Do not preempt kernel. Just maintain counter to know if task can be rescheduled.
> Asynchronous page fault may be delivered while spinlock is held or current
> process can't be preempted for other reasons. KVM uses preempt_count() to check if preemptions is allowed and schedule other process if possible. This works
> with preemptable kernels since they maintain accurate information about
> preemptability in preempt_count. This patch make non-preemptable kernel
> maintain accurate information in preempt_count too.

I'm thinking you're going to have to convince some people this won't
slow them down for no good.

Personally I always have PREEMPT=y, but other people seem to feel
strongly about not doing so.

--
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/