linux-kernel - Re: Why does the 2.6.37 scheduler hate RT tasks?

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] [day] [month] [year] [list]

Message-ID: <20110214151402.GA2256@linux.vnet.ibm.com>
Date:	Mon, 14 Feb 2011 07:14:02 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Yong Zhang <yong.zhang0@...il.com>
Cc:	peterz@...radead.org, linux-kernel@...r.kernel.org
Subject: Re: Why does the 2.6.37 scheduler hate RT tasks?

On Mon, Feb 14, 2011 at 10:55:49PM +0800, Yong Zhang wrote:
> On Tue, Feb 01, 2011 at 05:10:49PM -0800, Paul E. McKenney wrote:
> > Hello, Peter,
> > 
> > If I create an SCHED_FIFO-priority kthread in pre-2.6.37 kernels,
> > things work nicely.  If I try in in later kernels, __disable_runtime()
> > gets upset occasionally during CPU-hotplug calls when CPUs are inserted.
> > If I make the exact same kthreads run SCHED_NORMAL, no problem.
> > 
> > Unfortunately, I need an RT kthread so that I can do priority boosting.
> > 
> > My next thing to try is to demote my kthreads to SCHED_NORMAL at the
> > beginning of a CPU-hotplug event and promote them back to SCHED_FIFO at
> > the end of the CPU-hotplug event, which would leave the system vulnerable
> > to RCU priority inversion during CPU-hotplug events.  This would be
> > better than the current behavior, but I thought that I should check with
> > you to see if there is a better approach.
> 
> Just want to know the status of this issue :)
> 
> Does commit 06c3bc655697b19521901f9254eb0bbb2c67e7e8 cure it?

Ah, good to see that this got in!  I did extract it from the diagnostic
patch that Peter sent out, and it does seem to cure the issue.

							Thanx, Paul
--
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/