making PANIC_REBOOT_WAIT_TIME a tunable

[Colin Percival]

Hi all,

It seems that PANIC_REBOOT_WAIT_TIME has been a compile-time setting forever;
and I can't see any reason for this, but I assume there was one... at some
point in the distant past.

The attached patch makes it a loader tunable and sysctl.  My reason for wanting
this is to make EC2 images reboot faster after a panic (not that it happens
very often, of course) -- there's no point waiting for a key press at the
console because the EC2 console is output-only.

Any objections?

-- 
Colin Percival
Security Officer Emeritus, FreeBSD | The power to serve
Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid
-------------- next part --------------
Index: sys/kern/kern_shutdown.c
===================================================================
--- sys/kern/kern_shutdown.c	(revision 258085)
+++ sys/kern/kern_shutdown.c	(working copy)
@@ -89,6 +89,11 @@
 #ifndef PANIC_REBOOT_WAIT_TIME
 #define PANIC_REBOOT_WAIT_TIME 15 /* default to 15 seconds */
 #endif
+int panic_reboot_wait_time = PANIC_REBOOT_WAIT_TIME;
+SYSCTL_INT(_kern, OID_AUTO, panic_reboot_wait_time, CTLFLAG_RW | CTLFLAG_TUN,
+    &panic_reboot_wait_time, 0,
+    "Seconds to wait before rebooting after a panic");
+TUNABLE_INT("kern.panic_reboot_wait_time", &panic_reboot_wait_time);
 
 /*
  * Note that stdarg.h and the ANSI style va_start macro is used for both
@@ -485,12 +490,12 @@
 	int loop;
 
 	if (howto & RB_DUMP) {
-		if (PANIC_REBOOT_WAIT_TIME != 0) {
-			if (PANIC_REBOOT_WAIT_TIME != -1) {
+		if (panic_reboot_wait_time != 0) {
+			if (panic_reboot_wait_time != -1) {
 				printf("Automatic reboot in %d seconds - "
 				       "press a key on the console to abort\n",
-					PANIC_REBOOT_WAIT_TIME);
-				for (loop = PANIC_REBOOT_WAIT_TIME * 10;
+					panic_reboot_wait_time);
+				for (loop = panic_reboot_wait_time * 10;
 				     loop > 0; --loop) {
 					DELAY(1000 * 100); /* 1/10th second */
 					/* Did user type a key? */