linux-kernel - [PATCH 2/4 v3] x86, nmi: Add more flexible NMI back trace support

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Date:	Tue, 22 Apr 2014 11:17:26 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	akpm@...ux-foundation.org, x86@...nel.org, davem@...emloft.net,
	sparclinux@...r.kernel.org, mguzik@...hat.com,
	Aaron Tomlin <atomlin@...hat.com>,
	Don Zickus <dzickus@...hat.com>
Subject: [PATCH 2/4 v3] x86, nmi: Add more flexible NMI back trace support

From: Aaron Tomlin <atomlin@...hat.com>

This patch introduces the x86 specific implementation
changes to the arch_trigger_all_cpu_backtrace() routine.
Now users have the ability to choose whether or not to
issue an NMI back trace which includes current.

[Don't print message in single processor case,
 wrap with get/put_cpu based on Oleg's suggestion -dcz]

Signed-off-by: Aaron Tomlin <atomlin@...hat.com>
Signed-off-by: Don Zickus <dzickus@...hat.com>
---
 arch/x86/include/asm/irq.h    |    2 +-
 arch/x86/kernel/apic/hw_nmi.c |   17 +++++++++++++----
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/irq.h b/arch/x86/include/asm/irq.h
index cb6cfcd..a80cbb8 100644
--- a/arch/x86/include/asm/irq.h
+++ b/arch/x86/include/asm/irq.h
@@ -43,7 +43,7 @@ extern int vector_used_by_percpu_irq(unsigned int vector);
 extern void init_ISA_irqs(void);
 
 #ifdef CONFIG_X86_LOCAL_APIC
-void arch_trigger_all_cpu_backtrace(void);
+void arch_trigger_all_cpu_backtrace(bool);
 #define arch_trigger_all_cpu_backtrace arch_trigger_all_cpu_backtrace
 #endif
 
diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c
index a698d71..1400d72 100644
--- a/arch/x86/kernel/apic/hw_nmi.c
+++ b/arch/x86/kernel/apic/hw_nmi.c
@@ -33,31 +33,40 @@ static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
 /* "in progress" flag of arch_trigger_all_cpu_backtrace */
 static unsigned long backtrace_flag;
 
-void arch_trigger_all_cpu_backtrace(void)
+void arch_trigger_all_cpu_backtrace(bool include_self)
 {
 	int i;
+	int cpu = get_cpu();
 
-	if (test_and_set_bit(0, &backtrace_flag))
+	if (test_and_set_bit(0, &backtrace_flag)) {
 		/*
 		 * If there is already a trigger_all_cpu_backtrace() in progress
 		 * (backtrace_flag == 1), don't output double cpu dump infos.
 		 */
+		put_cpu();
 		return;
+	}
 
 	cpumask_copy(to_cpumask(backtrace_mask), cpu_online_mask);
+	if (!include_self)
+		cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
 
-	printk(KERN_INFO "sending NMI to all CPUs:\n");
-	apic->send_IPI_all(NMI_VECTOR);
+	if (!cpumask_empty(to_cpumask(backtrace_mask))) {
+		pr_info("sending NMI to %s CPUs:\n", (include_self ? "all" : "other"));
+		apic->send_IPI_mask(to_cpumask(backtrace_mask), NMI_VECTOR);
+	}
 
 	/* Wait for up to 10 seconds for all CPUs to do the backtrace */
 	for (i = 0; i < 10 * 1000; i++) {
 		if (cpumask_empty(to_cpumask(backtrace_mask)))
 			break;
 		mdelay(1);
+		touch_softlockup_watchdog();
 	}
 
 	clear_bit(0, &backtrace_flag);
 	smp_mb__after_clear_bit();
+	put_cpu();
 }
 
 static int __kprobes
-- 
1.7.1

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