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Subject[PATCH 6/9] x86: only call smp_processor_id in non-preempt cases
Date
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.

This was triggered by do_general_protection calling notify_die with
DIE_GPF.

Reported-by: Jan Kiszka <jan.kiszka@web.de>
Signed-off-by: Don Zickus <dzickus@redhat.com>
---
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 82bff25..ddb29bf 100644
--- a/arch/x86/kernel/apic/hw_nmi.c
+++ b/arch/x86/kernel/apic/hw_nmi.c
@@ -59,7 +59,7 @@ 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:
@@ -70,6 +70,7 @@ 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;
--
1.7.3.2


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