linux-kernel - [PATCH sched-devel 2/7] cpuisol: Do not route IRQs to the CPUs isolated at boot

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Date:	Fri, 22 Feb 2008 13:09:13 -0800
From:	Max Krasnyansky <maxk@...lcomm.com>
To:	mingo@...e.hu
Cc:	linux-kernel@...r.kernel.org, a.p.zijlstra@...llo.nl, pj@....com,
	Max Krasnyansky <maxk@...lcomm.com>
Subject: [PATCH sched-devel 2/7] cpuisol: Do not route IRQs to the CPUs isolated at boot

Most people would expect isolated CPUs to not get any
IRQs by default. This happens naturally if a CPU is brought
off-line, marked isolated and then brought back online.

There was some confusion about this patch originaly. So I wanted
to clarify that it does not completely disable IRQ handling on
the isolated CPUs. Users still have the option or routing IRQs
to them by modifying IRQ affinity mask.

I cannot test other archs hence the patch is for x86_64 only.

Signed-off-by: Max Krasnyansky <maxk@...lcomm.com>
---
 arch/x86/kernel/genapic_flat_64.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/genapic_flat_64.c b/arch/x86/kernel/genapic_flat_64.c
index 07352b7..e02e58c 100644
--- a/arch/x86/kernel/genapic_flat_64.c
+++ b/arch/x86/kernel/genapic_flat_64.c
@@ -21,7 +21,9 @@
 
 static cpumask_t flat_target_cpus(void)
 {
-	return cpu_online_map;
+	cpumask_t target;
+	cpus_andnot(target, cpu_online_map, cpu_isolated_map);
+	return target;
 }
 
 static cpumask_t flat_vector_allocation_domain(int cpu)
-- 
1.5.4.1

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