out of memory notifier.

diff -urpN linux-2.6/arch/s390/mm/cmm.c linux-2.6-oom/arch/s390/mm/cmm.c
@@ -16,6 +16,7 @@
 #include <linux/sched.h>
 #include <linux/sysctl.h>
 #include <linux/ctype.h>
+#include <linux/swap.h>
 
 #include <asm/pgalloc.h>
 #include <asm/uaccess.h>

@@ -44,6 +45,7 @@ static long cmm_timeout_seconds = 0;
 
 static struct cmm_page_array *cmm_page_list = NULL;
 static struct cmm_page_array *cmm_timed_page_list = NULL;
+static DEFINE_SPINLOCK(cmm_lock);
 
 static unsigned long cmm_thread_active = 0;
 static struct work_struct cmm_thread_starter;

@@ -72,40 +74,50 @@ cmm_strtoul(const char *cp, char **endp)
 static long
 cmm_alloc_pages(long pages, long *counter, struct cmm_page_array **list)
 {
-	struct cmm_page_array *pa;
+	struct cmm_page_array *pa, *npa;
 	unsigned long page;
 
-	pa = *list;
 	while (pages) {
 		page = __get_free_page(GFP_NOIO);
 		if (!page)
 			break;
+		spin_lock(&cmm_lock);
+		pa = *list;
 		if (!pa || pa->index >= CMM_NR_PAGES) {
 			/* Need a new page for the page list. */
-			pa = (struct cmm_page_array *)
+			spin_unlock(&cmm_lock);
+			npa = (struct cmm_page_array *)
 				__get_free_page(GFP_NOIO);
-			if (!pa) {
+			if (!npa) {
 				free_page(page);
 				break;
 			}
-			pa->next = *list;
-			pa->index = 0;
-			*list = pa;
+			spin_lock(&cmm_lock);
+			pa = *list;
+			if (!pa || pa->index >= CMM_NR_PAGES) {
+				npa->next = pa;
+				npa->index = 0;
+				pa = npa;
+				*list = pa;
+			} else
+				free_page((unsigned long) npa);
 		}
 		diag10(page);
 		pa->pages[pa->index++] = page;
 		(*counter)++;
+		spin_unlock(&cmm_lock);
 		pages--;
 	}
 	return pages;
 }
 
-static void
+static long
 cmm_free_pages(long pages, long *counter, struct cmm_page_array **list)
 {
 	struct cmm_page_array *pa;
 	unsigned long page;
 
+	spin_lock(&cmm_lock);
 	pa = *list;
 	while (pages) {
 		if (!pa || pa->index <= 0)

@@ -120,8 +132,29 @@ cmm_free_pages(long pages, long *counter
 		(*counter)--;
 		pages--;
 	}
+	spin_unlock(&cmm_lock);
+	return pages;
 }
 
+static int cmm_oom_notify(struct notifier_block *self,
+			  unsigned long dummy, void *parm)
+{
+	unsigned long *freed = parm;
+	long pages = 256;
+
+	pages = cmm_free_pages(pages, &cmm_timed_pages, &cmm_timed_page_list);
+	if (pages > 0)
+		pages = cmm_free_pages(pages, &cmm_pages, &cmm_page_list);
+	cmm_pages_target = cmm_pages;
+	cmm_timed_pages_target = cmm_timed_pages;
+	*freed += 256 - pages;
+	return NOTIFY_OK;
+}
+
+static struct notifier_block cmm_oom_nb = {
+	.notifier_call = cmm_oom_notify
+};
+
 static int
 cmm_thread(void *dummy)
 {

@@ -419,6 +452,7 @@ cmm_init (void)
 #ifdef CONFIG_CMM_IUCV
 	smsg_register_callback(SMSG_PREFIX, cmm_smsg_target);
 #endif
+	register_oom_notifier(&cmm_oom_nb);
 	INIT_WORK(&cmm_thread_starter, (void *) cmm_start_thread, NULL);
 	init_waitqueue_head(&cmm_thread_wait);
 	init_timer(&cmm_timer);

@@ -428,6 +462,7 @@ cmm_init (void)
 static void
 cmm_exit(void)
 {
+	unregister_oom_notifier(&cmm_oom_nb);
 	cmm_free_pages(cmm_pages, &cmm_pages, &cmm_page_list);
 	cmm_free_pages(cmm_timed_pages, &cmm_timed_pages, &cmm_timed_page_list);
 #ifdef CONFIG_CMM_PROC

diff -urpN linux-2.6/include/linux/swap.h linux-2.6-oom/include/linux/swap.h
@@ -7,6 +7,7 @@
 #include <linux/mmzone.h>
 #include <linux/list.h>
 #include <linux/sched.h>
+#include <linux/notifier.h>
 
 #include <asm/atomic.h>
 #include <asm/page.h>

@@ -157,6 +158,9 @@ struct swap_list_t {
 
 /* linux/mm/oom_kill.c */
 extern void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order);
+extern int register_oom_notifier(struct notifier_block *nb);
+extern int unregister_oom_notifier(struct notifier_block *nb);
+
 
 /* linux/mm/memory.c */
 extern void swapin_readahead(swp_entry_t, unsigned long, struct vm_area_struct *);

diff -urpN linux-2.6/mm/oom_kill.c linux-2.6-oom/mm/oom_kill.c
@@ -21,6 +21,7 @@
 #include <linux/timex.h>
 #include <linux/jiffies.h>
 #include <linux/cpuset.h>
+#include <linux/module.h>
 
 int sysctl_panic_on_oom;
 /* #define DEBUG */

@@ -306,6 +307,20 @@ static int oom_kill_process(struct task_
 	return oom_kill_task(p, message);
 }
 
+static struct notifier_block *oom_notify_list = 0;
+
+int register_oom_notifier(struct notifier_block *nb)
+{
+	return notifier_chain_register(&oom_notify_list, nb);
+}
+EXPORT_SYMBOL_GPL(register_oom_notifier);
+
+int unregister_oom_notifier(struct notifier_block *nb)
+{
+	return notifier_chain_unregister(&oom_notify_list, nb);
+}
+EXPORT_SYMBOL_GPL(unregister_oom_notifier);
+
 /**
  * out_of_memory - kill the "best" process when we run out of memory
  *

@@ -318,6 +333,12 @@ void out_of_memory(struct zonelist *zone
 {
 	task_t *p;
 	unsigned long points = 0;
+	unsigned long freed = 0;
+
+	notifier_call_chain(&oom_notify_list, 0, &freed);
+	if (freed > 0)
+		/* Got some memory back in the last second. */
+		return;
 
 	if (printk_ratelimit()) {
 		printk("oom-killer: gfp_mask=0x%x, order=%d\n",