[PATCH V2 4/5] panic: add 'panic_sys_info=' setup option for sysctl and kernel cmdline

[Feng Tang <feng.tang@linux.alibaba.com>]

Add 'panic_sys_info=' setup which expects string like "tasks,mem,lock,...".
It supports both runtime sysctl control and boot time kernel cmdline setup,
and could be seen as human readable string version of 'panic_print'.

The detail mapping is:
	SYS_SHOW_TASK_INFO	"tasks"
	SYS_SHOW_MEM_INFO	"mem"
	SYS_SHOW_TIMER_INFO	"timer"
	SYS_SHOW_LOCK_INFO	"lock"
	SYS_SHOW_FTRACE_INFO	"ftrace"
	SYS_SHOW_ALL_CPU_BT	"all_bt"
	SYS_SHOW_BLOCKED_TASKS	"blocked_tasks"

Suggested-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Feng Tang <feng.tang@linux.alibaba.com>
---
 .../admin-guide/kernel-parameters.txt          | 13 +++++++++++++
 Documentation/admin-guide/sysctl/kernel.rst    | 18 ++++++++++++++++++
 kernel/panic.c                                 | 16 ++++++++++++++++
 3 files changed, 47 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f1f2c0874da9..d714a0ebf909 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4541,6 +4541,19 @@
 			Use this option carefully, maybe worth to setup a
 			bigger log buffer with "log_buf_len" along with this.
 
+	panic_sys_info=
+			String of subsystem info to be dumped on panic.
+			It expects string of comma-separated words like
+			"tasks,mem,timer,...", which is a human readable string
+			version of 'panic_print':
+			tasks: print all tasks info
+			mem: print system memory info
+			timer: print timer info
+			lock: print locks info if CONFIG_LOCKDEP is on
+			ftrace: print ftrace buffer
+			all_bt: print all CPUs backtrace (if available in the arch)
+			blocked_tasks: print only tasks in uninterruptible (blocked) state
+
 	parkbd.port=	[HW] Parallel port number the keyboard adapter is
 			connected to, default is 0.
 			Format: <parport#>
diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index dd49a89a62d3..2013afd98605 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -899,6 +899,24 @@ So for example to print tasks and memory info on panic, user can::
   echo 3 > /proc/sys/kernel/panic_print
 
 
+panic_sys_info
+==============
+
+String of subsystem info to be dumped on panic. It expects string of
+comma-separated words like "tasks,mem,timer,...", which is a human
+readable string version of 'panic_print':
+
+=============   ===================================================
+tasks           print all tasks info
+mem             print system memory info
+timer           print timer info
+lock            print locks info if CONFIG_LOCKDEP is on
+ftrace          print ftrace buffer
+all_bt          print all CPUs backtrace (if available in the arch)
+blocked_tasks   print only tasks in uninterruptible (blocked) state
+=============   ===================================================
+
+
 panic_on_rcu_stall
 ==================
 
diff --git a/kernel/panic.c b/kernel/panic.c
index 35c98aefa39f..ea238f7d4b54 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -125,6 +125,13 @@ static const struct ctl_table kern_panic_table[] = {
 		.mode           = 0644,
 		.proc_handler   = proc_douintvec,
 	},
+	{
+		.procname	= "panic_sys_info",
+		.data		= &panic_print,
+		.maxlen         = sizeof(panic_print),
+		.mode		= 0644,
+		.proc_handler	= sysctl_sys_info_handler,
+	},
 };
 
 static __init int kernel_panic_sysctls_init(void)
@@ -135,6 +142,15 @@ static __init int kernel_panic_sysctls_init(void)
 late_initcall(kernel_panic_sysctls_init);
 #endif
 
+/* The format is "panic_sys_info=task,mem,ftrace,..." */
+static int __init setup_panic_sys_info(char *buf)
+{
+	/* There is no risk of race in kernel boot phase */
+	panic_print = sys_info_parse_param(buf);
+	return 1;
+}
+__setup("panic_sys_info=", setup_panic_sys_info);
+
 static atomic_t warn_count = ATOMIC_INIT(0);
 
 #ifdef CONFIG_SYSFS
-- 
2.39.5 (Apple Git-154)