linux-kernel - [tip:x86/apic] x86: Correct behaviour of irq affinity

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Message-ID: <tip-e06b1b56f9bfcc91e1f175fe8d8bf3e35dafa080@git.kernel.org>
Date:	Wed, 25 Mar 2009 17:51:28 GMT
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	yinghai@...nel.org, rusty@...tcorp.com.au, ebiederm@...ssion.com,
	akpm@...ux-foundation.org, tglx@...utronix.de, mingo@...e.hu
Subject: [tip:x86/apic] x86: Correct behaviour of irq affinity

Commit-ID:  e06b1b56f9bfcc91e1f175fe8d8bf3e35dafa080
Gitweb:     http://git.kernel.org/tip/e06b1b56f9bfcc91e1f175fe8d8bf3e35dafa080
Author:     Rusty Russell <rusty@...tcorp.com.au>
AuthorDate: Tue, 24 Mar 2009 14:17:19 -0700
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Wed, 25 Mar 2009 18:48:29 +0100

x86: Correct behaviour of irq affinity

Impact: get correct smp_affinity as user requested

The effect of setting desc->affinity (ie. from userspace via sysfs) has
varied over time.  In 2.6.27, the 32-bit code anded the value with
cpu_online_map, and both 32 and 64-bit did that anding whenever a cpu
was unplugged.

2.6.29 consolidated this into one routine (and fixed hotplug) but
introduced another variation: anding the affinity with cfg->domain.

We should just set it to what the user said - if possible.

(cpu_mask_to_apicid_and already takes cpu_online_mask into account)

Signed-off-by: Yinghai Lu <yinghai@...nel.org>
Acked-by: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
LKML-Reference: <49C94DDF.2010703@...nel.org>
Signed-off-by: Ingo Molnar <mingo@...e.hu>


---
 arch/x86/kernel/apic/io_apic.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 1ed6c06..d990408 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -594,9 +594,10 @@ set_desc_affinity(struct irq_desc *desc, const struct cpumask *mask)
 
 	/* check that before desc->addinity get updated */
 	set_extra_move_desc(desc, mask);
-	cpumask_and(desc->affinity, cfg->domain, mask);
 
-	return apic->cpu_mask_to_apicid_and(desc->affinity, cpu_online_mask);
+	cpumask_copy(desc->affinity, mask);
+
+	return apic->cpu_mask_to_apicid_and(desc->affinity, cfg->domain);
 }
 
 static void
--
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