linux-kernel - [tip:x86/apic] x86: fix set_extra_move

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Date:	Tue, 24 Mar 2009 21:15:31 GMT
From:	Yinghai Lu <yinghai@...nel.org>
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,
	tglx@...utronix.de, mingo@...e.hu
Subject: [tip:x86/apic] x86: fix set_extra_move_desc calling

Commit-ID:  fa74c9073370e57fa28e02aff13f4d7b1806505c
Gitweb:     http://git.kernel.org/tip/fa74c9073370e57fa28e02aff13f4d7b1806505c
Author:     Yinghai Lu <yinghai@...nel.org>
AuthorDate: Tue, 24 Mar 2009 13:23:16 -0700
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Tue, 24 Mar 2009 22:12:10 +0100

x86: fix set_extra_move_desc calling

Impact: fix bug with irq-descriptor moving when logical flat

Rusty observed:

> 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.  Is this right, or
> should we just set it to what the user said?  Or as now, indicate that we're
> restricting it.

Eric pointed out that desc->affinity should be what the user requested,
if it is at all possible to honor the user space request.

This bug got introduced by commit 22f65d31b "x86: Update io_apic.c to use
new cpumask API".

Fix it by moving the masking to before the descriptor moving ...

Reported-by: Rusty Russell <rusty@...tcorp.com.au>
Reported-by: Eric W. Biederman <ebiederm@...ssion.com>
LKML-Reference: <49C94134.4000408@...nel.org>
Signed-off-by: Ingo Molnar <mingo@...e.hu>


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

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 86827d8..1ed6c06 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -592,8 +592,9 @@ set_desc_affinity(struct irq_desc *desc, const struct cpumask *mask)
 	if (assign_irq_vector(irq, cfg, mask))
 		return BAD_APICID;
 
-	cpumask_and(desc->affinity, cfg->domain, 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);
 }
--
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