The patch titled
Subject: memcg: fix soft lockup in the OOM process
has been added to the -mm mm-unstable branch. Its filename is
memcg-fix-soft-lockup-in-the-oom-process.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/memcg-fix-soft-lockup-in-the-oom-process.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Chen Ridong <chenridong@xxxxxxxxxx>
Subject: memcg: fix soft lockup in the OOM process
Date: Tue, 24 Dec 2024 02:52:38 +0000
A soft lockup issue was found in the product with about 56,000 tasks were
in the OOM cgroup, it was traversing them when the soft lockup was
triggered.
watchdog: BUG: soft lockup - CPU#2 stuck for 23s! [VM Thread:1503066]
CPU: 2 PID: 1503066 Comm: VM Thread Kdump: loaded Tainted: G
Hardware name: Huawei Cloud OpenStack Nova, BIOS
RIP: 0010:console_unlock+0x343/0x540
RSP: 0000:ffffb751447db9a0 EFLAGS: 00000247 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 00000000ffffffff
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000247
RBP: ffffffffafc71f90 R08: 0000000000000000 R09: 0000000000000040
R10: 0000000000000080 R11: 0000000000000000 R12: ffffffffafc74bd0
R13: ffffffffaf60a220 R14: 0000000000000247 R15: 0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2fe6ad91f0 CR3: 00000004b2076003 CR4: 0000000000360ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
vprintk_emit+0x193/0x280
printk+0x52/0x6e
dump_task+0x114/0x130
mem_cgroup_scan_tasks+0x76/0x100
dump_header+0x1fe/0x210
oom_kill_process+0xd1/0x100
out_of_memory+0x125/0x570
mem_cgroup_out_of_memory+0xb5/0xd0
try_charge+0x720/0x770
mem_cgroup_try_charge+0x86/0x180
mem_cgroup_try_charge_delay+0x1c/0x40
do_anonymous_page+0xb5/0x390
handle_mm_fault+0xc4/0x1f0
This is because thousands of processes are in the OOM cgroup, it takes a
long time to traverse all of them. As a result, this lead to soft lockup
in the OOM process.
To fix this issue, call 'cond_resched' in the 'mem_cgroup_scan_tasks'
function per 1000 iterations. For global OOM, call
'touch_softlockup_watchdog' per 1000 iterations to avoid this issue.
Link: https://lkml.kernel.org/r/20241224025238.3768787-1-chenridong@xxxxxxxxxxxxxxx
Fixes: 9cbb78bb3143 ("mm, memcg: introduce own oom handler to iterate only over its own threads")
Signed-off-by: Chen Ridong <chenridong@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 7 ++++++-
mm/oom_kill.c | 8 +++++++-
2 files changed, 13 insertions(+), 2 deletions(-)
--- a/mm/memcontrol.c~memcg-fix-soft-lockup-in-the-oom-process
+++ a/mm/memcontrol.c
@@ -1161,6 +1161,7 @@ void mem_cgroup_scan_tasks(struct mem_cg
{
struct mem_cgroup *iter;
int ret = 0;
+ int i = 0;
BUG_ON(mem_cgroup_is_root(memcg));
@@ -1169,8 +1170,12 @@ void mem_cgroup_scan_tasks(struct mem_cg
struct task_struct *task;
css_task_iter_start(&iter->css, CSS_TASK_ITER_PROCS, &it);
- while (!ret && (task = css_task_iter_next(&it)))
+ while (!ret && (task = css_task_iter_next(&it))) {
+ /* Avoid potential softlockup warning */
+ if ((++i & 1023) == 0)
+ cond_resched();
ret = fn(task, arg);
+ }
css_task_iter_end(&it);
if (ret) {
mem_cgroup_iter_break(memcg, iter);
--- a/mm/oom_kill.c~memcg-fix-soft-lockup-in-the-oom-process
+++ a/mm/oom_kill.c
@@ -44,6 +44,7 @@
#include <linux/init.h>
#include <linux/mmu_notifier.h>
#include <linux/cred.h>
+#include <linux/nmi.h>
#include <asm/tlb.h>
#include "internal.h"
@@ -430,10 +431,15 @@ static void dump_tasks(struct oom_contro
mem_cgroup_scan_tasks(oc->memcg, dump_task, oc);
else {
struct task_struct *p;
+ int i = 0;
rcu_read_lock();
- for_each_process(p)
+ for_each_process(p) {
+ /* Avoid potential softlockup warning */
+ if ((++i & 1023) == 0)
+ touch_softlockup_watchdog();
dump_task(p, oc);
+ }
rcu_read_unlock();
}
}
_
Patches currently in -mm which might be from chenridong@xxxxxxxxxx are
mm-vmscan-retry-folios-written-back-while-isolated-for-traditional-lru.patch
memcg-fix-soft-lockup-in-the-oom-process.patch
