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From: Max Krasnyanskiy <maxk@qualcomm.com>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>, Daniel Walker <dwalker@mvista.com>
Subject: CPU hotplug and IRQ affinity with 2.6.24-rt1
Date: Mon, 04 Feb 2008 15:35:13 -0800	[thread overview]
Message-ID: <47A7A131.8040800@qualcomm.com> (raw)

This is just an FYI. As part of the "Isolated CPU extensions" thread Daniel suggest for me
to check out latest RT kernels. So I did or at least tried to and immediately spotted a couple
of issues.

The machine I'm running it on is:
	HP xw9300, Dual Opteron, NUMA

It looks like with -rt kernel IRQ affinity masks are ignored on that system. ie I write 1 to 
lets say /proc/irq/23/smp_affinity but the interrupts keep coming to CPU1. 
Vanilla 2.6.24 does not have that issue.

Also the first thing I tried was to bring CPU1 off-line. Thats the fastest way to get irqs, 
soft-irqs, timers, etc of a CPU. But the box hung completely. It also managed to mess up my 
ext3 filesystem to the point where it required manual fsck (have not see that for a couple of
years now). 
I tried the same thing (ie echo 0 > /sys/devices/cpu/cpu1/online) from the console. It hang 
again with the message that looked something like:
	CPU1 is now off-line
	Thread IRQ-23 is on CPU1 ...

IRQ 23 is NVidia SATA. So I guess it has something to do with the borked affinity handling.
Vanilla 2.6.24 handles this just fine.

Anyway, like I said it's just an FYI, not an urgent issue.

Max


             reply	other threads:[~2008-02-04 23:38 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-04 23:35 Max Krasnyanskiy [this message]
2008-02-05  2:51 ` Daniel Walker
2008-02-05  3:27   ` Gregory Haskins
2008-02-05  4:21   ` Max Krasnyansky
2008-02-05  5:02   ` Gregory Haskins
2008-02-05 16:59     ` Daniel Walker
2008-02-05 17:13       ` Gregory Haskins
2008-02-05 18:25       ` Gregory Haskins
2008-02-05 21:58         ` Daniel Walker
2008-02-05 22:03           ` Gregory Haskins
2008-02-05 14:00   ` Gregory Haskins

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