[tip:x86/uv] x86, UV: Fix smp_processor_id() use in a preemptable region

From: tip-bot for cpw@xxxxxxx
Date: Tue Jun 21 2011 - 11:16:33 EST

Commit-ID: 00b30cf04a775b5292ab704f782394e36e25617d
Gitweb: http://git.kernel.org/tip/00b30cf04a775b5292ab704f782394e36e25617d
Author: cpw@xxxxxxx <cpw@xxxxxxx>
AuthorDate: Tue, 21 Jun 2011 07:21:26 -0500
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Tue, 21 Jun 2011 14:50:31 +0200

x86, UV: Fix smp_processor_id() use in a preemptable region

Fix a call by tunables_write() to smp_processor_id() within a
preemptable region.

Call get_cpu()/put_cpu() around the region where the returned
cpu number is actually used, which makes it non-preemptable.

A DEBUG_PREEMPT warning is prevented.

UV does not support cpu hotplug yet, but this is a step toward
that ability as well.

Signed-off-by: Cliff Wickman <cpw@xxxxxxx>
Link: http://lkml.kernel.org/r/20110621122242.086384966@xxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
arch/x86/platform/uv/tlb_uv.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/platform/uv/tlb_uv.c b/arch/x86/platform/uv/tlb_uv.c
index 68e467f..34be650 100644
--- a/arch/x86/platform/uv/tlb_uv.c
+++ b/arch/x86/platform/uv/tlb_uv.c
@@ -1334,9 +1334,10 @@ static ssize_t tunables_write(struct file *file, const char __user *user,

instr[count] = '\0';

- bcp = &per_cpu(bau_control, smp_processor_id());
+ cpu = get_cpu();
+ bcp = &per_cpu(bau_control, cpu);
ret = parse_tunables_write(bcp, instr, count);
+ put_cpu();
if (ret)
return ret;

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