linux-kernel - [PATCH 1/8 v2] x86, UV: smp_processor

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Date:	Wed, 15 Jun 2011 10:46:56 -0500
From:	Cliff Wickman <cpw@....com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...e.hu
Subject: [PATCH 1/8 v2] x86, UV: smp_processor_id in a preemptable region

From: Cliff Wickman <cpw@....com>

Calling smp_processor_id() from within a preemptable region will issue
a warning if DEBUG_PREEMPT is set.

Which cpu is returned by smp_processor_id() is actually arbitrary here, as
every cpu has a per-cpu structure with the needed limit for the tunable. But
the call should be non-preemptable to avoid a warning in a DEBUG_PREEMPT
kernel.

Diffed against 3.0.0-rc3

Signed-off-by: Cliff Wickman <cpw@....com>
---
 arch/x86/platform/uv/tlb_uv.c |    2 ++
 1 file changed, 2 insertions(+)

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
@@ -1334,7 +1334,9 @@ static ssize_t tunables_write(struct fil
 
 	instr[count] = '\0';
 
+	preempt_disable(); /* avoid DEBUG_PREEMPT warning */
 	bcp = &per_cpu(bau_control, smp_processor_id());
+	preempt_enable_no_resched();
 
 	ret = parse_tunables_write(bcp, instr, count);
 	if (ret)
--
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