[PATCH] x86: all cpu backtrace

When a spinlock lockup occurs, arrange for the NMI code to emit an all-cpu
backtrace, so we get to see which CPU is holding the lock, and where.

Cc: Andi Kleen <ak@muc.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Andi Kleen <ak@suse.de>

3 files changed, 16 insertions, 0 deletions

diff --git a/include/asm-i386/nmi.h b/include/asm-i386/nmi.h
index 269d315719ca..b04333ea6f31 100644
--- a/include/asm-i386/nmi.h
+++ b/include/asm-i386/nmi.h
@@ -5,6 +5,9 @@
 #define ASM_NMI_H
 
 #include <linux/pm.h>
+#include <asm/irq.h>
+
+#ifdef ARCH_HAS_NMI_WATCHDOG
 
 /**
  * do_nmi_callback
@@ -42,4 +45,9 @@ extern int proc_nmi_enabled(struct ctl_table *, int , struct file *,
                         void __user *, size_t *, loff_t *);
 extern int unknown_nmi_panic;
 
+void __trigger_all_cpu_backtrace(void);
+#define trigger_all_cpu_backtrace() __trigger_all_cpu_backtrace()
+
+#endif
+
 #endif /* ASM_NMI_H */
diff --git a/include/asm-x86_64/nmi.h b/include/asm-x86_64/nmi.h
index f367d4014b42..72375e7d32a8 100644
--- a/include/asm-x86_64/nmi.h
+++ b/include/asm-x86_64/nmi.h
@@ -77,4 +77,7 @@ extern int proc_nmi_enabled(struct ctl_table *, int , struct file *,
 
 extern int unknown_nmi_panic;
 
+void __trigger_all_cpu_backtrace(void);
+#define trigger_all_cpu_backtrace() __trigger_all_cpu_backtrace()
+
 #endif /* ASM_NMI_H */
diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index e16904e28c3a..acb4ed130247 100644
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -15,9 +15,14 @@
  * disables interrupts for a long time. This call is stateless.
  */
 #ifdef ARCH_HAS_NMI_WATCHDOG
+#include <asm/nmi.h>
 extern void touch_nmi_watchdog(void);
 #else
 # define touch_nmi_watchdog() touch_softlockup_watchdog()
 #endif
 
+#ifndef trigger_all_cpu_backtrace
+#define trigger_all_cpu_backtrace() do { } while (0)
+#endif
+
 #endif