[PATCH] 2.4 and 2.5: remove Alt-Sysrq-L

The following patch removes Alt-Sysrq-L and its associated hack to kill
of PID1, the init process.  This is a mis-feature.

If PID1 is killed, the kernel immediately enters an infinite loop in the
depths of do_exit() with interrupts disabled, completely locking the
machine.  Obviously you can only reach for the reset button or power
switch after this, leaving you with dirty filesystems.

drivers/char/sysrq.c

@@ -284,24 +284,20 @@ static struct sysrq_key_op sysrq_showmem_op = {
 
 /* signal sysrq helper function
  * Sends a signal to all user processes */
-static void send_sig_all(int sig, int even_init)
+static void send_sig_all(int sig)
 {
 	struct task_struct *p;
 
 	for_each_task(p) {
-		if (p->mm) { /* Not swapper nor kernel thread */
-			if (p->pid == 1 && even_init)
-				/* Ugly hack to kill init */
-				p->pid = 0x8000;
-			if (p->pid != 1)
+		if (p->mm && p->pid != 1)
+			/* Not swapper, init nor kernel thread */
 			force_sig(sig, p);
 	}
-	}
 }
 
 static void sysrq_handle_term(int key, struct pt_regs *pt_regs,
 		struct kbd_struct *kbd, struct tty_struct *tty) {
-	send_sig_all(SIGTERM, 0);
+	send_sig_all(SIGTERM);
 	console_loglevel = 8;
 }
 static struct sysrq_key_op sysrq_term_op = {
@@ -312,7 +308,7 @@ static struct sysrq_key_op sysrq_term_op = {
 
 static void sysrq_handle_kill(int key, struct pt_regs *pt_regs,
 		struct kbd_struct *kbd, struct tty_struct *tty) {
-	send_sig_all(SIGKILL, 0);
+	send_sig_all(SIGKILL);
 	console_loglevel = 8;
 }
 static struct sysrq_key_op sysrq_kill_op = {
@@ -321,17 +317,6 @@ static struct sysrq_key_op sysrq_kill_op = {
 	action_msg:	"Kill All Tasks",
 };
 
-static void sysrq_handle_killall(int key, struct pt_regs *pt_regs,
-		struct kbd_struct *kbd, struct tty_struct *tty) {
-	send_sig_all(SIGKILL, 1);
-	console_loglevel = 8;
-}
-static struct sysrq_key_op sysrq_killall_op = {
-	handler:	sysrq_handle_killall,
-	help_msg:	"killalL",
-	action_msg:	"Kill All Tasks (even init)",
-};
-
 /* END SIGNAL SYSRQ HANDLERS BLOCK */
 
 
@@ -366,7 +351,7 @@ static struct sysrq_key_op *sysrq_key_table[SYSRQ_KEY_TABLE_LENGTH] = {
 #else
 /* k */	NULL,
 #endif
-/* l */	&sysrq_killall_op,
+/* l */	NULL,
 /* m */	&sysrq_showmem_op,
 /* n */	NULL,
 /* o */	NULL, /* This will often be registered