From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Frank Rowand <frank.rowand@am.sony.com>,
"paulmck@linux.vnet.ibm.com" <paulmck@linux.vnet.ibm.com>,
"Rowand, Frank" <Frank_Rowand@sonyusa.com>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-rt-users <linux-rt-users@vger.kernel.org>,
Mike Galbraith <efault@gmx.de>, Ingo Molnar <mingo@tglx.de>,
Venkatesh Pallipadi <venki@google.com>
Subject: Re: [ANNOUNCE] 3.0.1-rt11
Date: Wed, 7 Sep 2011 15:01:30 +0100 [thread overview]
Message-ID: <20110907140130.GT6619@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <alpine.LFD.2.02.1109071254010.2723@ionos>
On Wed, Sep 07, 2011 at 12:57:44PM +0200, Thomas Gleixner wrote:
> The problem is that if you enable interrupts on the CPU _BEFORE_ it is
> set online AND active, then you can end up waking up kernel threads
> which are bound to that CPU and the scheduler will happily schedule
> them on an online CPU. That makes them lose the cpu affinity to the
> CPU as well and hell breaks lose.
How can that happen?
1. The only interrupts we're likely to receive are the local timer
interrupts - we have not routed any other interrupts to this CPU.
2. We will not schedule on this CPU except at explicit scheduling
points (such as contended mutexes or explicit calls to schedule)
as we have a call to preempt_disable().
> Frank has observed this with softirq threads, but the same thing is
> true for any other CPU bound thread like the worker stuff.
So who is scheduling a workqueue from the local timer?
> So moving the online, active thing BEFORE enabling interrupt is the
> only sensible solution.
Yes, that'll be why even x86 enables interrupts before setting the CPU
online for the delay calibration.
next prev parent reply other threads:[~2011-09-07 14:02 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-13 10:53 [ANNOUNCE] 3.0.1-rt11 Peter Zijlstra
2011-08-13 11:48 ` Mike Galbraith
2011-08-13 11:58 ` Peter Zijlstra
2011-08-13 13:59 ` Mike Galbraith
2011-08-13 14:23 ` Peter Zijlstra
2011-08-13 16:27 ` Paul E. McKenney
2011-08-14 4:23 ` Mike Galbraith
2011-08-16 14:17 ` Nivedita Singhvi
2011-08-16 15:10 ` Mike Galbraith
2011-08-16 15:18 ` Nivedita Singhvi
2011-08-16 19:31 ` Paul E. McKenney
2011-08-17 4:28 ` Mike Galbraith
2011-08-17 5:03 ` Nivedita Singhvi
2011-08-15 10:09 ` Mike Galbraith
2011-08-14 21:19 ` Clark Williams
2011-08-21 8:30 ` patches/mm-memory-rt.patch can go away Mike Galbraith
2011-08-23 14:12 ` [patch] sched, rt: fix migrate_enable() thinko Mike Galbraith
2011-09-08 2:11 ` Frank Rowand
2011-09-08 4:58 ` Mike Galbraith
2011-08-24 23:58 ` [ANNOUNCE] 3.0.1-rt11 Frank Rowand
2011-08-26 23:55 ` Paul E. McKenney
2011-08-29 19:57 ` Frank Rowand
2011-08-30 3:17 ` Paul E. McKenney
2011-09-07 2:53 ` Frank Rowand
2011-09-07 3:00 ` Frank Rowand
2011-09-07 3:00 ` Frank Rowand
2011-09-07 6:42 ` Paul E. McKenney
2011-09-07 9:25 ` Thomas Gleixner
2011-09-07 9:25 ` Thomas Gleixner
2011-09-07 10:46 ` Russell King - ARM Linux
2011-09-07 10:47 ` Russell King - ARM Linux
2011-09-07 10:57 ` Thomas Gleixner
2011-09-07 14:01 ` Russell King - ARM Linux [this message]
2011-09-07 16:32 ` Thomas Gleixner
2011-09-07 16:33 ` Frank Rowand
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