[patch 1/8 v4] x86, UV: smp_processor_id in a preemptable region

From: cpw
Date: Thu Jun 16 2011 - 11:53:59 EST

Fix a call by tunables_write() to smp_processor_id() within a preemptable
Call get_cpu()/put_cpu() around the region where the returned cpu
number is actually used, which makes it non-preemptable.

Diffed against 3.0.0-rc3

Signed-off-by: Cliff Wickman <cpw@xxxxxxx>

A DEBUG_PREEMPT warning is prevented.
UV does not support cpu hotplug yet, but this is a step toward that ability.

arch/x86/platform/uv/tlb_uv.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

Index: linux/arch/x86/platform/uv/tlb_uv.c
--- linux.orig/arch/x86/platform/uv/tlb_uv.c
+++ linux/arch/x86/platform/uv/tlb_uv.c
@@ -1334,9 +1334,10 @@ static ssize_t tunables_write(struct fil

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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