Revision 03049269de433cb5fe2859be9ae4469ceb1163ed authored by Michal Hocko on 25 March 2016, 21:20:33 UTC, committed by Linus Torvalds on 25 March 2016, 23:37:42 UTC
wake_oom_reaper has allowed only 1 oom victim to be queued. The main reason for that was the simplicity as other solutions would require some way of queuing. The current approach is racy and that was deemed sufficient as the oom_reaper is considered a best effort approach to help with oom handling when the OOM victim cannot terminate in a reasonable time. The race could lead to missing an oom victim which can get stuck out_of_memory wake_oom_reaper cmpxchg // OK oom_reaper oom_reap_task __oom_reap_task oom_victim terminates atomic_inc_not_zero // fail out_of_memory wake_oom_reaper cmpxchg // fails task_to_reap = NULL This race requires 2 OOM invocations in a short time period which is not very likely but certainly not impossible. E.g. the original victim might have not released a lot of memory for some reason. The situation would improve considerably if wake_oom_reaper used a more robust queuing. This is what this patch implements. This means adding oom_reaper_list list_head into task_struct (eat a hole before embeded thread_struct for that purpose) and a oom_reaper_lock spinlock for queuing synchronization. wake_oom_reaper will then add the task on the queue and oom_reaper will dequeue it. Signed-off-by: Michal Hocko <mhocko@suse.com> Cc: Vladimir Davydov <vdavydov@virtuozzo.com> Cc: Andrea Argangeli <andrea@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent bc448e8
plist.c
/*
* lib/plist.c
*
* Descending-priority-sorted double-linked list
*
* (C) 2002-2003 Intel Corp
* Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>.
*
* 2001-2005 (c) MontaVista Software, Inc.
* Daniel Walker <dwalker@mvista.com>
*
* (C) 2005 Thomas Gleixner <tglx@linutronix.de>
*
* Simplifications of the original code by
* Oleg Nesterov <oleg@tv-sign.ru>
*
* Licensed under the FSF's GNU Public License v2 or later.
*
* Based on simple lists (include/linux/list.h).
*
* This file contains the add / del functions which are considered to
* be too large to inline. See include/linux/plist.h for further
* information.
*/
#include <linux/bug.h>
#include <linux/plist.h>
#ifdef CONFIG_DEBUG_PI_LIST
static struct plist_head test_head;
static void plist_check_prev_next(struct list_head *t, struct list_head *p,
struct list_head *n)
{
WARN(n->prev != p || p->next != n,
"top: %p, n: %p, p: %p\n"
"prev: %p, n: %p, p: %p\n"
"next: %p, n: %p, p: %p\n",
t, t->next, t->prev,
p, p->next, p->prev,
n, n->next, n->prev);
}
static void plist_check_list(struct list_head *top)
{
struct list_head *prev = top, *next = top->next;
plist_check_prev_next(top, prev, next);
while (next != top) {
prev = next;
next = prev->next;
plist_check_prev_next(top, prev, next);
}
}
static void plist_check_head(struct plist_head *head)
{
if (!plist_head_empty(head))
plist_check_list(&plist_first(head)->prio_list);
plist_check_list(&head->node_list);
}
#else
# define plist_check_head(h) do { } while (0)
#endif
/**
* plist_add - add @node to @head
*
* @node: &struct plist_node pointer
* @head: &struct plist_head pointer
*/
void plist_add(struct plist_node *node, struct plist_head *head)
{
struct plist_node *first, *iter, *prev = NULL;
struct list_head *node_next = &head->node_list;
plist_check_head(head);
WARN_ON(!plist_node_empty(node));
WARN_ON(!list_empty(&node->prio_list));
if (plist_head_empty(head))
goto ins_node;
first = iter = plist_first(head);
do {
if (node->prio < iter->prio) {
node_next = &iter->node_list;
break;
}
prev = iter;
iter = list_entry(iter->prio_list.next,
struct plist_node, prio_list);
} while (iter != first);
if (!prev || prev->prio != node->prio)
list_add_tail(&node->prio_list, &iter->prio_list);
ins_node:
list_add_tail(&node->node_list, node_next);
plist_check_head(head);
}
/**
* plist_del - Remove a @node from plist.
*
* @node: &struct plist_node pointer - entry to be removed
* @head: &struct plist_head pointer - list head
*/
void plist_del(struct plist_node *node, struct plist_head *head)
{
plist_check_head(head);
if (!list_empty(&node->prio_list)) {
if (node->node_list.next != &head->node_list) {
struct plist_node *next;
next = list_entry(node->node_list.next,
struct plist_node, node_list);
/* add the next plist_node into prio_list */
if (list_empty(&next->prio_list))
list_add(&next->prio_list, &node->prio_list);
}
list_del_init(&node->prio_list);
}
list_del_init(&node->node_list);
plist_check_head(head);
}
/**
* plist_requeue - Requeue @node at end of same-prio entries.
*
* This is essentially an optimized plist_del() followed by
* plist_add(). It moves an entry already in the plist to
* after any other same-priority entries.
*
* @node: &struct plist_node pointer - entry to be moved
* @head: &struct plist_head pointer - list head
*/
void plist_requeue(struct plist_node *node, struct plist_head *head)
{
struct plist_node *iter;
struct list_head *node_next = &head->node_list;
plist_check_head(head);
BUG_ON(plist_head_empty(head));
BUG_ON(plist_node_empty(node));
if (node == plist_last(head))
return;
iter = plist_next(node);
if (node->prio != iter->prio)
return;
plist_del(node, head);
plist_for_each_continue(iter, head) {
if (node->prio != iter->prio) {
node_next = &iter->node_list;
break;
}
}
list_add_tail(&node->node_list, node_next);
plist_check_head(head);
}
#ifdef CONFIG_DEBUG_PI_LIST
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/init.h>
static struct plist_node __initdata test_node[241];
static void __init plist_test_check(int nr_expect)
{
struct plist_node *first, *prio_pos, *node_pos;
if (plist_head_empty(&test_head)) {
BUG_ON(nr_expect != 0);
return;
}
prio_pos = first = plist_first(&test_head);
plist_for_each(node_pos, &test_head) {
if (nr_expect-- < 0)
break;
if (node_pos == first)
continue;
if (node_pos->prio == prio_pos->prio) {
BUG_ON(!list_empty(&node_pos->prio_list));
continue;
}
BUG_ON(prio_pos->prio > node_pos->prio);
BUG_ON(prio_pos->prio_list.next != &node_pos->prio_list);
prio_pos = node_pos;
}
BUG_ON(nr_expect != 0);
BUG_ON(prio_pos->prio_list.next != &first->prio_list);
}
static void __init plist_test_requeue(struct plist_node *node)
{
plist_requeue(node, &test_head);
if (node != plist_last(&test_head))
BUG_ON(node->prio == plist_next(node)->prio);
}
static int __init plist_test(void)
{
int nr_expect = 0, i, loop;
unsigned int r = local_clock();
printk(KERN_DEBUG "start plist test\n");
plist_head_init(&test_head);
for (i = 0; i < ARRAY_SIZE(test_node); i++)
plist_node_init(test_node + i, 0);
for (loop = 0; loop < 1000; loop++) {
r = r * 193939 % 47629;
i = r % ARRAY_SIZE(test_node);
if (plist_node_empty(test_node + i)) {
r = r * 193939 % 47629;
test_node[i].prio = r % 99;
plist_add(test_node + i, &test_head);
nr_expect++;
} else {
plist_del(test_node + i, &test_head);
nr_expect--;
}
plist_test_check(nr_expect);
if (!plist_node_empty(test_node + i)) {
plist_test_requeue(test_node + i);
plist_test_check(nr_expect);
}
}
for (i = 0; i < ARRAY_SIZE(test_node); i++) {
if (plist_node_empty(test_node + i))
continue;
plist_del(test_node + i, &test_head);
nr_expect--;
plist_test_check(nr_expect);
}
printk(KERN_DEBUG "end plist test\n");
return 0;
}
module_init(plist_test);
#endif
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