[PATCH] x86: add sysctl for kstack_depth_to_print

Add sysctl for kstack_depth_to_print. This lets users change
the amount of raw stack data printed in dump_stack() without
having to reboot.

Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
Signed-off-by: Andi Kleen <ak@suse.de>

Documentation/sysctl/kernel.txt

@@ -27,6 +27,7 @@ show up in /proc/sys/kernel:
 - hotplug
 - java-appletviewer           [ binfmt_java, obsolete ]
 - java-interpreter            [ binfmt_java, obsolete ]
+- kstack_depth_to_print       [ X86 only ]
 - l2cr                        [ PPC only ]
 - modprobe                    ==> Documentation/kmod.txt
 - msgmax
@@ -170,6 +171,13 @@ This flag controls the L2 cache of G3 processor boards. If
 
 ==============================================================
 
+kstack_depth_to_print: (X86 only)
+
+Controls the number of words to print when dumping the raw
+kernel stack.
+
+==============================================================
+
 osrelease, ostype & version:
 
 # cat osrelease

arch/i386/kernel/traps.c

@@ -91,7 +91,7 @@ asmlinkage void alignment_check(void);
 asmlinkage void spurious_interrupt_bug(void);
 asmlinkage void machine_check(void);
 
-static int kstack_depth_to_print = 24;
+int kstack_depth_to_print = 24;
 #ifdef CONFIG_STACK_UNWIND
 static int call_trace = 1;
 #else

arch/x86_64/kernel/traps.c

@@ -108,7 +108,7 @@ static inline void preempt_conditional_cli(struct pt_regs *regs)
 	preempt_enable_no_resched();
 }
 
-static int kstack_depth_to_print = 12;
+int kstack_depth_to_print = 12;
 #ifdef CONFIG_STACK_UNWIND
 static int call_trace = 1;
 #else

include/asm-x86_64/stacktrace.h

@@ -1,6 +1,8 @@
 #ifndef _ASM_STACKTRACE_H
 #define _ASM_STACKTRACE_H 1
 
+extern int kstack_depth_to_print;
+
 /* Generic stack tracer with callbacks */
 
 struct stacktrace_ops {

kernel/sysctl.c

@@ -54,6 +54,7 @@ extern int proc_nr_files(ctl_table *table, int write, struct file *filp,
 
 #ifdef CONFIG_X86
 #include <asm/nmi.h>
+#include <asm/stacktrace.h>
 #endif
 
 #if defined(CONFIG_SYSCTL)
@@ -707,6 +708,14 @@ static ctl_table kern_table[] = {
 		.mode		= 0444,
 		.proc_handler	= &proc_dointvec,
 	},
+	{
+		.ctl_name	= CTL_UNNUMBERED,
+		.procname	= "kstack_depth_to_print",
+		.data		= &kstack_depth_to_print,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec,
+	},
 #endif
 #if defined(CONFIG_MMU)
 	{