[PATCH v3 2/2] kernel/sysctl: Add panic_print into sysctl

[Feng Tang]

So that we can also runtime chose to print out the needed
system info for panic, other than setting the kernel cmdline.

Suggested-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: John Stultz <john.stultz@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
---
 Documentation/sysctl/kernel.txt | 17 +++++++++++++++++
 include/linux/kernel.h          |  1 +
 include/uapi/linux/sysctl.h     |  1 +
 kernel/panic.c                  |  2 +-
 kernel/sysctl.c                 |  7 +++++++
 kernel/sysctl_binary.c          |  1 +
 6 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 1b87752..c0527d8 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -60,6 +60,7 @@ show up in /proc/sys/kernel:
 - panic_on_stackoverflow
 - panic_on_unrecovered_nmi
 - panic_on_warn
+- panic_print
 - panic_on_rcu_stall
 - perf_cpu_time_max_percent
 - perf_event_paranoid
@@ -654,6 +655,22 @@ a kernel rebuild when attempting to kdump at the location of a WARN().
 
 ==============================================================
 
+panic_print:
+
+Bitmask for printing system info when panic happens. User can chose
+combination of the following bits:
+
+bit 0: print all tasks info
+bit 1: print system memory info
+bit 2: print timer info
+bit 3: print locks info if CONFIG_LOCKDEP is on
+bit 4: print ftrace buffer
+
+So for example to print tasks and memory info on panic, user can:
+  echo 3 > /proc/sys/kernel/panic_print
+
+==============================================================
+
 panic_on_rcu_stall:
 
 When set to 1, calls panic() after RCU stall detection messages. This
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index d6aac75..8f0e68e 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -527,6 +527,7 @@ static inline u32 int_sqrt64(u64 x)
 extern void bust_spinlocks(int yes);
 extern int oops_in_progress;		/* If set, an oops, panic(), BUG() or die() is in progress */
 extern int panic_timeout;
+extern unsigned long panic_print;
 extern int panic_on_oops;
 extern int panic_on_unrecovered_nmi;
 extern int panic_on_io_nmi;
diff --git a/include/uapi/linux/sysctl.h b/include/uapi/linux/sysctl.h
index d71013f..87aa2a6 100644
--- a/include/uapi/linux/sysctl.h
+++ b/include/uapi/linux/sysctl.h
@@ -153,6 +153,7 @@ enum
 	KERN_NMI_WATCHDOG=75, /* int: enable/disable nmi watchdog */
 	KERN_PANIC_ON_NMI=76, /* int: whether we will panic on an unrecovered */
 	KERN_PANIC_ON_WARN=77, /* int: call panic() in WARN() functions */
+	KERN_PANIC_PRINT=78, /* ulong: bitmask to print system info on panic */
 };
 
 
diff --git a/kernel/panic.c b/kernel/panic.c
index fb6ccd1..85c4d14 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -50,7 +50,7 @@ EXPORT_SYMBOL_GPL(panic_timeout);
 #define PANIC_PRINT_TIMER_INFO		0x00000004
 #define PANIC_PRINT_LOCK_INFO		0x00000008
 #define PANIC_PRINT_FTRACE_INFO		0x00000010
-static unsigned long panic_print;
+unsigned long panic_print;
 
 ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
 
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 5fc724e..818da9a 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -807,6 +807,13 @@ static struct ctl_table kern_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec,
 	},
+	{
+		.procname	= "panic_print",
+		.data		= &panic_print,
+		.maxlen		= sizeof(unsigned long),
+		.mode		= 0644,
+		.proc_handler	= proc_doulongvec_minmax,
+	},
 #if defined CONFIG_PRINTK
 	{
 		.procname	= "printk",
diff --git a/kernel/sysctl_binary.c b/kernel/sysctl_binary.c
index 07148b4..73c1320 100644
--- a/kernel/sysctl_binary.c
+++ b/kernel/sysctl_binary.c
@@ -140,6 +140,7 @@ static const struct bin_table bin_kern_table[] = {
 	{ CTL_INT,	KERN_MAX_LOCK_DEPTH,		"max_lock_depth" },
 	{ CTL_INT,	KERN_PANIC_ON_NMI,		"panic_on_unrecovered_nmi" },
 	{ CTL_INT,	KERN_PANIC_ON_WARN,		"panic_on_warn" },
+	{ CTL_ULONG,	KERN_PANIC_PRINT,		"panic_print" },
 	{}
 };
 
-- 
2.7.4