Re: [PATCH 5.10.y] memcg: fix soft lockup in the OOM process

[Sasha Levin <sashal@kernel.org>]

[ Sasha's backport helper bot ]

Hi,

Summary of potential issues:
❌ Build failures detected

The upstream commit SHA1 provided is correct: ade81479c7dda1ce3eedb215c78bc615bbd04f06

WARNING: Author mismatch between patch and upstream commit:
Backport author: Abdelkareem Abdelsaamad<kareemem@amazon.com>
Commit author: Chen Ridong<chenridong@huawei.com>

Status in newer kernel trees:
6.13.y | Present (different SHA1: 465768342918)
6.12.y | Present (different SHA1: c3a3741db8c1)
6.6.y | Present (different SHA1: 972486d37169)
6.1.y | Present (different SHA1: 0a09d56e1682)
5.15.y | Present (different SHA1: a9042dbc1ed4)

Note: The patch differs from the upstream commit:
---
Failed to apply patch cleanly.
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-5.10.y       |  Failed     |  N/A       |

Build Errors:
Patch failed to apply on stable/linux-5.10.y. Reject:

diff a/mm/memcontrol.c b/mm/memcontrol.c	(rejected hunks)
@@ -1312,6 +1312,7 @@ int mem_cgroup_scan_tasks(struct mem_cgroup *memcg,
 {
 	struct mem_cgroup *iter;
 	int ret = 0;
+	int i = 0;
 
 	BUG_ON(memcg == root_mem_cgroup);
 
@@ -1320,8 +1321,12 @@ int mem_cgroup_scan_tasks(struct mem_cgroup *memcg,
 		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);
diff a/mm/oom_kill.c b/mm/oom_kill.c	(rejected hunks)
@@ -43,6 +43,7 @@
 #include <linux/kthread.h>
 #include <linux/init.h>
 #include <linux/mmu_notifier.h>
+#include <linux/nmi.h>
 
 #include <asm/tlb.h>
 #include "internal.h"
@@ -430,10 +431,15 @@ static void dump_tasks(struct oom_control *oc)
 		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();
 	}
 }