From: Cliff Wickman <[email protected]>
Calling smp_processor_id() from within a preemptable region will issue
a warning if DEBUG_PREEMPT is set.
The calls to get_cpu()/put_cpu() bound the region where the return cpu
number is actually used and make it non-preemptable. A DEBUG_PREEMPT
warning is prevented.
UV does not support cpu hotplug yet, but this is a step toward that ability.
Diffed against 3.0.0-rc3
Signed-off-by: Cliff Wickman <[email protected]>
---
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;