From: Larry Woodman <lwoodman@redhat.com>
Subject: [RHEL5 patch] Fix broken AltSysrq-F (Force OOM kill functionality)
Date: Thu, 12 Jul 2007 14:12:10 -0400
Bugzilla: 251731
Message-Id: <46966EFA.1070504@redhat.com>
Changelog: [misc] Fix broken AltSysrq-F



Back in RHEL5-GA timeframe I ported the RHEL4 out_of_memory() logic
to RHEL5 because it OOM killed much to aggressively.   That change broke
the new AltSysrq-F/Force OOM kill functionality that was introduce in the
2.6.17 timeframe.  Actually it didnt "break" the functionality, it 
"changed" it
so that multiple AltSysrq-F keystrokes are required to manually OOM kill
a task.  This isnt a very big deal since no one is going to be forcing 
OOM kills
via AltSysrq so its not worth respinning for just this but, it is broken 
and should
be fixed some time.  The following patch fixes that problem:



--- linux-2.6.18.noarch/drivers/char/sysrq.c.orig
+++ linux-2.6.18.noarch/drivers/char/sysrq.c
@@ -252,7 +252,7 @@ static struct sysrq_key_op sysrq_term_op
 static void moom_callback(void *ignored)
 {
 	out_of_memory(&NODE_DATA(0)->node_zonelists[ZONE_NORMAL],
-			GFP_KERNEL, 0);
+			GFP_KERNEL, 0, 1);
 }
 
 static DECLARE_WORK(moom_work, moom_callback, NULL);
--- linux-2.6.18.noarch/include/linux/swap.h.orig
+++ linux-2.6.18.noarch/include/linux/swap.h
@@ -159,7 +159,7 @@ struct swap_list_t {
 #define vm_swap_full() (nr_swap_pages*2 < total_swap_pages)
 
 /* linux/mm/oom_kill.c */
-extern void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order);
+extern void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order, int force);
 extern int register_oom_notifier(struct notifier_block *nb);
 extern int unregister_oom_notifier(struct notifier_block *nb);
 
--- linux-2.6.18.noarch/mm/oom_kill.c.orig
+++ linux-2.6.18.noarch/mm/oom_kill.c
@@ -443,7 +443,7 @@ EXPORT_SYMBOL_GPL(unregister_oom_notifie
  * 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.
  */
-void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order)
+void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order, int force)
 {
 	struct task_struct *p;
 	unsigned long points = 0;
@@ -454,6 +454,9 @@ void out_of_memory(struct zonelist *zone
 		/* Got some memory back in the last second. */
 		return;
 
+	if (!should_oom_kill() && !force)
+		return;
+
 	if (printk_ratelimit()) {
 		printk(KERN_WARNING "%s invoked oom-killer: "
 		"gfp_mask=0x%x, order=%d, oomkilladj=%d\n",
@@ -462,9 +465,6 @@ void out_of_memory(struct zonelist *zone
 		show_mem();
 	}
 
-	if (!should_oom_kill())
-		return;
-
 	cpuset_lock();
 	read_lock(&tasklist_lock);
 
--- linux-2.6.18.noarch/mm/page_alloc.c.orig
+++ linux-2.6.18.noarch/mm/page_alloc.c
@@ -1026,7 +1026,7 @@ rebalance:
 		if (page)
 			goto got_pg;
 
-		out_of_memory(zonelist, gfp_mask, order);
+		out_of_memory(zonelist, gfp_mask, order, 0);
 		goto restart;
 	}