linux-kernel - [tip:perf/core] x86: Only call smp_processor

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Date:	Wed, 5 Jan 2011 14:07:33 GMT
From:	tip-bot for Don Zickus <dzickus@...hat.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	jan.kiszka@....de, tglx@...utronix.de, mingo@...e.hu,
	dzickus@...hat.com
Subject: [tip:perf/core] x86: Only call smp_processor_id in non-preempt cases

Commit-ID:  9ab181fa9ff73a38fccd0a4f1c40a38dfe62b535
Gitweb:     http://git.kernel.org/tip/9ab181fa9ff73a38fccd0a4f1c40a38dfe62b535
Author:     Don Zickus <dzickus@...hat.com>
AuthorDate: Tue, 4 Jan 2011 22:38:07 -0500
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Wed, 5 Jan 2011 14:22:57 +0100

x86: Only call smp_processor_id in non-preempt cases

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@....de>
Signed-off-by: Don Zickus <dzickus@...hat.com>
LKML-Reference: <1294198689-15447-1-git-send-email-dzickus@...hat.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 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 c57d0b5..2b40a60 100644
--- a/arch/x86/kernel/apic/hw_nmi.c
+++ b/arch/x86/kernel/apic/hw_nmi.c
@@ -51,7 +51,7 @@ 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:
@@ -63,6 +63,7 @@ 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;
--
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