x86: fix trigger_all_cpu_backtrace() implementation

Fix the x86 implementation of trigger_all_cpu_backtrace(), which was
previously (accidentally, as far as I can tell) disabled to always return
false as on architectures that do not implement this function.

trigger_all_cpu_backtrace(), as defined in include/linux/nmi.h, should
call arch_trigger_all_cpu_backtrace() if available, or return false if the
underlying arch doesn't implement this function.

x86 did provide a suitable arch_trigger_all_cpu_backtrace()
implementation, but it wasn't actually being used because it was declared
in asm/nmi.h, which linux/nmi.h doesn't include.  Also, linux/nmi.h
couldn't easily be fixed by including asm/nmi.h, because that file is not
available on all architectures.

I am proposing to fix this by moving the x86 definition of
arch_trigger_all_cpu_backtrace() to asm/irq.h.

Tested: echo l > /proc/sysrq-trigger

Before the change, this uses a fallback implementation which shows
backtraces on active CPUs (using smp_call_function_interrupt()).

After the change, this shows NMI backtraces on all CPUs.

Signed-off-by: Michel Lespinasse <walken@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/arch/x86/include/asm/irq.h b/arch/x86/include/asm/irq.h
index ba870bb6dd8ef30ab81a317a8eb43dcb83066630..57873beb32927426b3f5c5c97284729195d2c2e5 100644 (file)
--- a/arch/x86/include/asm/irq.h
+++ b/arch/x86/include/asm/irq.h
@@ -41,4 +41,9 @@ 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);
+#define arch_trigger_all_cpu_backtrace arch_trigger_all_cpu_backtrace
+#endif
+
 #endif /* _ASM_X86_IRQ_H */

diff --git a/arch/x86/include/asm/nmi.h b/arch/x86/include/asm/nmi.h
index c0fa356e90de24ea60ba8a0ac90c39e6bb05d73b..86f9301903c818c632b227537b44142b71883c8d 100644 (file)
--- a/arch/x86/include/asm/nmi.h
+++ b/arch/x86/include/asm/nmi.h
@@ -18,9 +18,7 @@ extern int proc_nmi_enabled(struct ctl_table *, int ,
                        void __user *, size_t *, loff_t *);
 extern int unknown_nmi_panic;
 
-void arch_trigger_all_cpu_backtrace(void);
-#define arch_trigger_all_cpu_backtrace arch_trigger_all_cpu_backtrace
-#endif
+#endif /* CONFIG_X86_LOCAL_APIC */
 
 #define NMI_FLAG_FIRST 1
 

diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c
index 31cb9ae992b7d7921b03bd6173068bae3138a06e..a698d7165c96a5b8fc0c08c8ee7f419b52933b08 100644 (file)
--- a/arch/x86/kernel/apic/hw_nmi.c
+++ b/arch/x86/kernel/apic/hw_nmi.c
@@ -9,6 +9,7 @@
  *
  */
 #include <asm/apic.h>
+#include <asm/nmi.h>
 
 #include <linux/cpumask.h>
 #include <linux/kdebug.h>