[patch] trivial sysrq addon

[patch] trivial sysrq addon

[Christian Leber]

Hello,

my box (2.6.9-final) was yesterday completly stalled (mouse movable and
stupid loadmeter was still working) after starting mutt and was swapping
for half an hour until I sent SIGTERM to all processes.
I suspect it was a 2 GB big galeon process that was the problem.

I think sysrq needs a key to call oom_kill manually.


Christian Leber

---

--- linux-2.6.10-rc1.orig/drivers/char/sysrq.c	2004-10-22 23:40:06.000000000 +0200
+++ linux-2.6.10-rc1/drivers/char/sysrq.c	2004-10-23 18:02:18.000000000 +0200
@@ -35,6 +35,7 @@
 #include <linux/spinlock.h>
 
 #include <asm/ptrace.h>
+extern void oom_kill(void);
 
 extern void reset_vc(unsigned int);
 
@@ -202,6 +203,18 @@
 	.action_msg	= "Terminate All Tasks",
 };
 
+static void sysrq_handle_moom(int key, struct pt_regs *pt_regs,
+			      struct tty_struct *tty) 
+{
+	oom_kill();
+//	console_loglevel = 8;
+}
+static struct sysrq_key_op sysrq_moom_op = {
+	.handler	= sysrq_handle_moom,
+	.help_msg	= "Full",
+	.action_msg	= "Manual OOM execution",
+};
+
 static void sysrq_handle_kill(int key, struct pt_regs *pt_regs,
 			      struct tty_struct *tty) 
 {
@@ -238,7 +251,7 @@
 /* c */ NULL,
 /* d */	NULL,
 /* e */	&sysrq_term_op,
-/* f */	NULL,
+/* f */	&sysrq_moom_op,
 /* g */	NULL,
 /* h */	NULL,
 /* i */	&sysrq_kill_op,
--- linux-2.6.10-rc1.orig/mm/oom_kill.c	2004-10-22 23:39:20.000000000 +0200
+++ linux-2.6.10-rc1/mm/oom_kill.c	2004-10-23 19:16:47.000000000 +0200
@@ -184,7 +184,7 @@
  * OR try to be smart about which process to kill. Note that we
  * don't have to be perfect here, we just have to be good.
  */
-static void oom_kill(void)
+void oom_kill(void)
 {
 	struct mm_struct *mm;
 	struct task_struct *g, *p, *q;
@@ -214,13 +214,6 @@
 		printk(KERN_INFO "Fixed up OOM kill of mm-less task\n");
 	read_unlock(&tasklist_lock);
 	mmput(mm);
-
-	/*
-	 * Make kswapd go out of the way, so "p" has a good chance of
-	 * killing itself before someone else gets the chance to ask
-	 * for more memory.
-	 */
-	yield();
 	return;
 }
 
@@ -284,6 +277,12 @@
 	/* oom_kill() sleeps */
 	spin_unlock(&oom_lock);
 	oom_kill();
+	/*
+	 * Make kswapd go out of the way, so "p" has a good chance of
+	 * killing itself before someone else gets the chance to ask
+	 * for more memory.
+	 */
+	yield();
 	spin_lock(&oom_lock);
 
 reset:
--- linux-2.6.10-rc1.orig/Documentation/sysrq.txt	2004-10-22 23:39:19.000000000 +0200
+++ linux-2.6.10-rc1/Documentation/sysrq.txt	2004-10-23 19:35:37.000000000 +0200
@@ -73,6 +73,8 @@
           it so that only emergency messages like PANICs or OOPSes would
           make it to your console.)
 
+'f'	- Will call oom_kill to kill a memory hog process
+
 'e'     - Send a SIGTERM to all processes, except for init.
 
 'i'     - Send a SIGKILL to all processes, except for init.

Re: [patch] trivial sysrq addon

[Andrew Morton]

Christian Leber <christian@leber.de> wrote:
>
> Hello,
> 
> my box (2.6.9-final) was yesterday completly stalled (mouse movable and
> stupid loadmeter was still working) after starting mutt and was swapping
> for half an hour until I sent SIGTERM to all processes.
> I suspect it was a 2 GB big galeon process that was the problem.

heh, fair enough.

> I think sysrq needs a key to call oom_kill manually.
> 

I'm wondering how you chose 'f'.

> --- linux-2.6.10-rc1.orig/drivers/char/sysrq.c	2004-10-22 23:40:06.000000000 +0200
> +++ linux-2.6.10-rc1/drivers/char/sysrq.c	2004-10-23 18:02:18.000000000 +0200
> @@ -35,6 +35,7 @@
>  #include <linux/spinlock.h>
>  
>  #include <asm/ptrace.h>
> +extern void oom_kill(void);

Well you'll never go to heaven.  I'll move this declaration to mm.h.

Re: [patch] trivial sysrq addon

[Andrew Morton]

Christian Leber <christian@leber.de> wrote:
>
> I think sysrq needs a key to call oom_kill manually.

oy, you can't do that - oom_kill() takes non-IRQ-safe locks.

You'll have to use schedule_work() to punt the operation up to process
context.