linux-kernel - Re: [PATCH V2] x86/irq: Cure live lock in fixup

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Date:	Thu, 17 Mar 2016 14:14:40 -0700
From:	"Luck, Tony" <tony.luck@...el.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Harry Junior <harryjr@...look.fr>, x86@...nel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Joe Lawrence <joe.lawrence@...atus.com>,
	Borislav Petkov <bp@...en8.de>,
	Ben Hutchings <ben@...adent.org.uk>
Subject: Re: [PATCH V2] x86/irq: Cure live lock in fixup_irqs()

This version also passes repeated iterations of:

# echo 0 | tee /sys/devices/system/cpu/cpu*/online
# echo 1 | tee /sys/devices/system/cpu/cpu*/online

Some of the time taken in the offline cycle may be
a more than O(N) chasing of IRQs onto an ever smaller
available set of online cpus.  There are over 4000
lines like this:

[  218.220045] Broke affinity for irq 66

on the console for each offline pass.

Also a couple of these:

[  221.951171] IRQ fixup: irq 68 move in progress, old vector 79

for each pass offlining all but one cpu.

Tested-by: Tony Luck <tony.luck@...el.com>

-Tony