linux-kernel - Re: [PATCH] kmod: Run usermodehelpers only on cpus allowed for kthreadd

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: <00000141d7066bf8-4a725d00-cdf3-430f-b6a9-616e180918a9-000000@email.amazonses.com>
Date:	Sun, 20 Oct 2013 18:00:24 +0000
From:	Christoph Lameter <cl@...ux.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Galbraith <bitbucket@...ine.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Gilad Ben-Yossef <gilad@...yossef.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Mike Frysinger <vapier@...too.org>
Subject: Re: [PATCH] kmod: Run usermodehelpers only on cpus allowed for
 kthreadd

On Fri, 18 Oct 2013, Frederic Weisbecker wrote:

> Makes sense yeah. In fact what I'm mostly concerned about is that we should
> set the affinity of __call_usermodehelper threads through inheritance from
> a parent rather than making it setting its affinity itself. Because in the latter case,
> the usermodehelper thread can run anywhere until it sets its affinity. Whether
> this little window of global affinity is short or not, this defeats the initial purpose
> of this patch that is about isolating CPUs and having them undisturbed.
>
> May be we can do that by setting the affinity of the "khelper" workqueue?

The "parent" for usemodehelper in this case is keventd. The worker queue
item is triggered on a particular processor and thats fine because that is
the result of an OS action or a device irq action. These can already be
avoided. What is not ok is that a process makes a move onto a hardware
thread where we want to have the least OS holdoffs possible.

Setting it via khelper would be fine. Any objections?

--
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/