[PATCH 1/3] x86: only call smp_processor_id in non-preempt cases

From: Don Zickus
Date: Fri Nov 12 2010 - 09:51:13 EST


There are some paths that walk the die_chain with preemption on.
Make sure we are in an NMI call before we start doing anything.

Reported-by: Jan Kiszka <jan.kiszka@xxxxxx>
Signed-off-by: Don Zickus <dzickus@xxxxxxxxxx>
---
arch/x86/kernel/apic/hw_nmi.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c
index 5c4f952..ef4755d 100644
--- a/arch/x86/kernel/apic/hw_nmi.c
+++ b/arch/x86/kernel/apic/hw_nmi.c
@@ -49,7 +49,7 @@ arch_trigger_all_cpu_backtrace_handler(struct notifier_block *self,
{
struct die_args *args = __args;
struct pt_regs *regs;
- int cpu = smp_processor_id();
+ int cpu;

switch (cmd) {
case DIE_NMI:
@@ -60,6 +60,7 @@ arch_trigger_all_cpu_backtrace_handler(struct notifier_block *self,
}

regs = args->regs;
+ cpu = smp_processor_id();

if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
static arch_spinlock_t lock = __ARCH_SPIN_LOCK_UNLOCKED;
--
1.7.2.3

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