linux-kernel - Re: [PATCH v8 08/14] nohz_full: allow disabling the 1Hz minimum tick at boot

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 for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 21 Oct 2015 17:35:01 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Chris Metcalf <cmetcalf@...hip.com>,
	Gilad Ben Yossef <giladb@...hip.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>, Tejun Heo <tj@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Andy Lutomirski <luto@...capital.net>,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 08/14] nohz_full: allow disabling the 1Hz minimum tick
 at boot

On Wed, Oct 21, 2015 at 09:28:04AM -0500, Christoph Lameter wrote:
> On Tue, 20 Oct 2015, Frederic Weisbecker wrote:
> 
> > There have been proposals to disable/tune the 1 Hz tick via debugfs which
> > I Nacked because once you give such an opportunity to the users, they
> > will use that hack and never fix the real underlying issue.
> 
> Well this is a pretty bad argument. By that reasoning no one should be
> allowed to use root. After all stupid users will become root and kill
> processes that are hung. And the underlying issue that causes those hangs
> in processes will never be fixed because they will keep on killing
> processes.

I disagree. There is an signifiant frontier between:

_ hack it up and you're responsible of the consequences, yourself

      and
      
_ provide a buggy hack to the user and support this officially upstream


Especially as all I've seen in two years, wrt. solving the 1 Hz issue, is patches like this.
Almost nobody really tried to dig into the real issues that are well known and identified
after all now, and not that hard to fix: it's many standalone issues to make the scheduler
resilient with full-total-hard-dynticks.

The only effort toward that I've seen lately is:  https://lkml.org/lkml/2015/10/14/192
and still I think the author came to that nohz issue by accident.

Many users are too easily happy with hacks like this and that one is a too much a good
opportunity for them.
--
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/