linux-kernel - Re: [PATCH] nohz: Prevent broadcast source from stealing full dynticks timekeeping duty

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: <alpine.LFD.2.02.1305301554100.2905@ionos>
Date:	Thu, 30 May 2013 15:57:17 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Frederic Weisbecker <fweisbec@...il.com>
cc:	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>, Jiri Bohac <jbohac@...e.cz>,
	Steven Rostedt <rostedt@...dmis.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH] nohz: Prevent broadcast source from stealing full dynticks
 timekeeping duty

On Wed, 29 May 2013, Frederic Weisbecker wrote:

> The timekeeping duty is currently assigned to the CPU that
> handles the tick broadcast clock device by the time it is set in
> one shot mode.
> 
> The reason for this is not entirely clear as outlined by Jiri
> Bohac: https://patchwork.kernel.org/patch/2302951/
> 
> One could speculate though that it makes sure only one CPU
> is woken up to fixup the timekeeping max deferment. But the
> timekeeper can change anytime after the broadcast CPU becomes
> idle. So probably we can remove this as in Jiri's patch, but
> not late in the -rc's.

Looking at commit 7300711e (clockevents: broadcast fixup possible
waiters) which introduced that takeover, I really can't see a reason
why we must do that. It's safe to remove it completely even now.

Thanks,

	tglx




--
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/