sysrq: add debug message to reboot event

Add debug message to detect keyboard vs non-keyboard triggered sysrq-b events.

Signed-off-by Tina Yang <[email protected]>

Signed-off-by Zach Brown <[email protected]>

---

--- linux-2.6.git/drivers/char/sysrq.c.orig 2009-08-13
15:43:34.000000000 -0700
+++ linux-2.6.git/drivers/char/sysrq.c 2009-08-13 21:51:15.832694000 -0700

(quoted diff) +10 -5

@@ -135,17 +135,22 @@ static struct sysrq_key_op sysrq_crash_o
        .enable_mask    = SYSRQ_ENABLE_DUMP,
 };
 
-static void sysrq_handle_reboot(int key, struct tty_struct *tty)
+static void sysrq_handle_reboot(int check_mask, int key, struct
 tty_struct *tty)
 {
+       if (check_mask)
+               printk("<keyboard-invoked>\n");
+        else
+               printk("<non-keyboard-invoked: PID %d COMMAND %s>\n",
+                               current->pid, current->comm);
        lockdep_off();
        local_irq_enable();
        emergency_restart();
 }
 static struct sysrq_key_op sysrq_reboot_op = {
-       .handler        = sysrq_handle_reboot,
-       .help_msg       = "reBoot",
-       .action_msg     = "Resetting",
-       .enable_mask    = SYSRQ_ENABLE_BOOT,
+       .handler_with_mask      = sysrq_handle_reboot,
+       .help_msg               = "reBoot",
+       .action_msg             = "Resetting",
+       .enable_mask            = SYSRQ_ENABLE_BOOT,
 };
 

static void sysrq_handle_sync(int key, struct tty_struct *tty)

(quoted diff) +4 -1

@@ -509,7 +514,10 @@ void __handle_sysrq(int key, struct tty_
                if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
                        printk("%s\n", op_p->action_msg);
                        console_loglevel = orig_log_level;
-                       op_p->handler(key, tty);
+                       if (op_p->handler_with_mask)
+                               op_p->handler_with_mask(check_mask, key,
 tty);
+                       else
+                               op_p->handler(key, tty);
                } else {
                        printk("This sysrq operation is disabled.\n");

                }

--- linux-2.6.git/include/linux/sysrq.h.orig 2009-08-13
20:53:48.085786000 -0700
+++ linux-2.6.git/include/linux/sysrq.h 2009-08-13 20:54:12.625756000 -0700

Quoted 6 lines · tina.yang

Add debug message to detect keyboard vs non-keyboard triggered sysrq-b events.

Signed-off-by Tina Yang <[email protected]>

Signed-off-by Zach Brown <[email protected]>

...

I'd rather have this go through -mm, this doesn't really fully qualify for trivial tree. CCing Andrew.

The changelog had no description of why the change should be applied and I was unable to understand the motivation from reading the patch, so I skipped it.

Also the patch was wordwrapped and had all its tabs replaced by spaces.

Add debug message to detect keyboard vs non-keyboard triggered sysrq-b events. This is to assist postmortem debugging on complicated computing setup with large number of applications involved where reboot event had occurred, but unclear of its origin.

Quoted 5 lines · On Wed, 19 Aug 2009 19:22:16 -0700 "tina.yang" <[email protected]> wrote:

Add debug message to detect keyboard vs non-keyboard triggered sysrq-b events. This is to assist postmortem debugging on complicated computing setup with large number of applications involved where reboot event had occurred, but unclear of its origin.

I'm still struggling to understand the motivation for the change. There are a large number of ways in which a machine can be rebooted, all the way down to a triple-fault. So it seems fairly arbitrary to add additional information to discriminate between just two of those ways.

I assume that somewhere in your setup you have a script which does `echo b /proc/sysrq-trigger' and it took ages to work out that this was happening and you felt that having this code in place would have helped you debug that problem, yes?

If so, I wonder what is the likelihood that someone else will have the same problem and will find this change useful.

Perhaps we should do this for all sysrq events rather than just sysrq-b?

drivers/char/sysrq.c

Quoted 3 lines

drivers/char/sysrq.c renamed from drivers/char/sysrq.c.orig +0 -0

2.6.18 is truly ancient and this patch doesn't apply at all to current development kernels.