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

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Date:	Mon, 14 Feb 2011 22:55:49 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	peterz@...radead.org, linux-kernel@...r.kernel.org
Subject: Re: Why does the 2.6.37 scheduler hate RT tasks?

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?

Thanks,
Yong
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