[PATCH] 2.4.3 and SysRq over serial console

[PATCH] 2.4.3 and SysRq over serial console

[Tom Rini]

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Hello all.  Without the attached patch, SysRq doesn't work over a serial
console here.  Has anyone else seen this problem?

-- 
Tom Rini (TR1265)
http://gate.crashing.org/~trini/

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diff -Nru a/linux/drivers/char/n_tty.c b/linux/drivers/char/n_tty.c
--- a/linux/drivers/char/n_tty.c	Sat Mar 31 16:30:44 2001
+++ b/linux/drivers/char/n_tty.c	Sat Mar 31 16:30:44 2001
@@ -40,6 +40,10 @@
 #include <linux/string.h>
 #include <linux/slab.h>
 #include <linux/poll.h>
+#ifdef CONFIG_MAGIC_SYSRQ	/* Handle the SysRq Hack */
+#include <linux/sysrq.h>
+#include <linux/console.h>
+#endif
 
 #include <asm/uaccess.h>
 #include <asm/system.h>
@@ -458,6 +462,12 @@
 
 static inline void n_tty_receive_break(struct tty_struct *tty)
 {
+#ifdef CONFIG_MAGIC_SYSRQ	/* Handle the SysRq Hack */
+	struct console *c = console_drivers;
+	if (c && c->device && (c->device(c) == tty->device)
+	    && !test_and_change_bit(TTY_DOING_SYSRQ, &tty->flags))
+		return;
+#endif
 	if (I_IGNBRK(tty))
 		return;
 	if (I_BRKINT(tty)) {
@@ -506,6 +516,12 @@
 {
 	unsigned long flags;
 
+#ifdef CONFIG_MAGIC_SYSRQ	/* Handle the SysRq Hack */
+	if (test_and_clear_bit(TTY_DOING_SYSRQ, &tty->flags)) {
+		handle_sysrq(c, NULL, NULL, tty);
+		return;
+	}
+#endif
 	if (tty->raw) {
 		put_tty_queue(c, tty);
 		return;
diff -Nru a/linux/include/linux/tty.h b/linux/include/linux/tty.h
--- a/linux/include/linux/tty.h	Sat Mar 31 16:30:44 2001
+++ b/linux/include/linux/tty.h	Sat Mar 31 16:30:44 2001
@@ -329,6 +329,9 @@
 #define TTY_PUSH 6
 #define TTY_CLOSING 7
 #define TTY_DONT_FLIP 8
+#ifdef CONFIG_MAGIC_SYSRQ	/* Handle the SysRq Hack */
+#define TTY_DOING_SYSRQ 9
+#endif
 #define TTY_HW_COOK_OUT 14
 #define TTY_HW_COOK_IN 15
 #define TTY_PTY_LOCK 16

Re: [PATCH] 2.4.3 and SysRq over serial console

[Russell King]

On Sat, Mar 31, 2001 at 04:38:08PM -0700, Tom Rini wrote:
> Hello all.  Without the attached patch, SysRq doesn't work over a serial
> console here.  Has anyone else seen this problem?

It is handled at the serial port driver level, not the tty level.  You need
to turn on CONFIG_SERIAL_CONSOLE and CONFIG_MAGIC_SYSRQ, and issue a break
followed by the relevent character within 5 seconds on the serial TTY being
used as the kernel console.

--
Russell King (rmk@arm.linux.org.uk)                The developer of ARM Linux
             http://www.arm.linux.org.uk/personal/aboutme.html

Re: [PATCH] 2.4.3 and SysRq over serial console

[Tom Rini]

On Tue, Apr 03, 2001 at 09:07:44PM +0100, Russell King wrote:
> On Sat, Mar 31, 2001 at 04:38:08PM -0700, Tom Rini wrote:
> > Hello all.  Without the attached patch, SysRq doesn't work over a serial
> > console here.  Has anyone else seen this problem?
> 
> It is handled at the serial port driver level, not the tty level.  You need
> to turn on CONFIG_SERIAL_CONSOLE and CONFIG_MAGIC_SYSRQ, and issue a break
> followed by the relevent character within 5 seconds on the serial TTY being
> used as the kernel console.

That wasn't working here however.  Unless minicom isn't sending the proper
break.  Doing the keycombo which slips my mind to send a break, followed by
'h' in minicom does nothing.

-- 
Tom Rini (TR1265)
http://gate.crashing.org/~trini/

Re: [PATCH] 2.4.3 and SysRq over serial console

[Tom Rini]

On Tue, Apr 03, 2001 at 09:07:44PM +0100, Russell King wrote:
> On Sat, Mar 31, 2001 at 04:38:08PM -0700, Tom Rini wrote:
> > Hello all.  Without the attached patch, SysRq doesn't work over a serial
> > console here.  Has anyone else seen this problem?
> 
> It is handled at the serial port driver level, not the tty level.  You need
> to turn on CONFIG_SERIAL_CONSOLE and CONFIG_MAGIC_SYSRQ, and issue a break
> followed by the relevent character within 5 seconds on the serial TTY being
> used as the kernel console.

After talking with the person who originally did the patch, yeah, that does
make sense (and the serial driver we're using needs to be fixed).  Thanks.

-- 
Tom Rini (TR1265)
http://gate.crashing.org/~trini/