linux-kernel - [RFC PATCH 1/2] IRQ: use cpu_possible_mask rather than online_mask in setup

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Message-Id: <1285629463-27699-2-git-send-email-nacc@us.ibm.com>
Date:	Mon, 27 Sep 2010 16:17:42 -0700
From:	Nishanth Aravamudan <nacc@...ibm.com>
To:	nacc@...ibm.com
Cc:	miltonm@....com, Thomas Gleixner <tglx@...utronix.de>,
	Ian Campbell <ian.campbell@...rix.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@...el.com>,
	linux-kernel@...r.kernel.org
Subject: [RFC PATCH 1/2] IRQ: use cpu_possible_mask rather than online_mask in setup_affinity

The use of online_mask requires architecture code to be hotplug-aware to
account for IRQ round-robin'ing. With user-driven dynamic SMT, this
could commonly occur even without physical hotplug. Without this change
and "pseries/xics: use cpu_possible_mask rather than cpu_all_mask", IRQs
are all routed to CPU0 on power machines not running irqbalance.

Signed-off-by: Nishanth Aravamudan <nacc@...ibm.com>
---
I have boot-tested this on ppc64, but not yet on x86/x86_64. This is
generic-code, and perhaps an audit of all .set_affinity functions should
occur before upstream acceptance?

 kernel/irq/manage.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index c3003e9..ef85b95 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -175,7 +175,7 @@ static int setup_affinity(unsigned int irq, struct irq_desc *desc)
 			desc->status &= ~IRQ_AFFINITY_SET;
 	}
 
-	cpumask_and(desc->affinity, cpu_online_mask, irq_default_affinity);
+	cpumask_and(desc->affinity, cpu_possible_mask, irq_default_affinity);
 set_affinity:
 	desc->chip->set_affinity(irq, desc->affinity);
 
-- 
1.7.0.4

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