* [PATCH] mm/oom_kill: simplify remaining RCU sections with guard(rcu)
@ 2026-08-13 3:26 Ye Liu
2026-08-13 8:49 ` Michal Hocko
0 siblings, 1 reply; 3+ messages in thread
From: Ye Liu @ 2026-08-13 3:26 UTC (permalink / raw)
To: Michal Hocko, Andrew Morton
Cc: Ye Liu, David Rientjes, Shakeel Butt, linux-mm, linux-kernel
From: Ye Liu <liuye@kylinos.cn>
Replace the remaining manual rcu_read_lock()/rcu_read_unlock() pairs
in oom_cpuset_eligible(), select_bad_process(), dump_tasks(),
task_will_free_mem(), and __oom_kill_process() with guard(rcu)() for
consistency and simpler control flow.
Signed-off-by: Ye Liu <liuye@kylinos.cn>
---
mm/oom_kill.c | 15 +++++----------
1 file changed, 5 insertions(+), 10 deletions(-)
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 4b5c70aaece4..8bbb5ca00bb6 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -94,7 +94,7 @@ static bool oom_cpuset_eligible(struct task_struct *start,
bool ret = false;
const nodemask_t *mask = oc->nodemask;
- rcu_read_lock();
+ guard(rcu)();
for_each_thread(start, tsk) {
if (mask) {
/*
@@ -114,7 +114,6 @@ static bool oom_cpuset_eligible(struct task_struct *start,
if (ret)
break;
}
- rcu_read_unlock();
return ret;
}
@@ -368,11 +367,10 @@ static void select_bad_process(struct oom_control *oc)
else {
struct task_struct *p;
- rcu_read_lock();
+ guard(rcu)();
for_each_process(p)
if (oom_evaluate_task(p, oc))
break;
- rcu_read_unlock();
}
}
@@ -430,14 +428,13 @@ static void dump_tasks(struct oom_control *oc)
struct task_struct *p;
int i = 0;
- rcu_read_lock();
+ guard(rcu)();
for_each_process(p) {
/* Avoid potential softlockup warning */
if ((++i & 1023) == 0)
touch_softlockup_watchdog();
dump_task(p, oc);
}
- rcu_read_unlock();
}
}
@@ -894,7 +891,7 @@ static bool task_will_free_mem(struct task_struct *task)
* are dying as well to make sure that a) nobody pins its mm and
* b) the task is also reapable by the oom reaper.
*/
- rcu_read_lock();
+ guard(rcu)();
for_each_process(p) {
if (!process_shares_mm(p, mm))
continue;
@@ -904,7 +901,6 @@ static bool task_will_free_mem(struct task_struct *task)
if (!ret)
break;
}
- rcu_read_unlock();
return ret;
}
@@ -960,7 +956,7 @@ static void __oom_kill_process(struct task_struct *victim, const char *message)
* That thread will now get access to memory reserves since it has a
* pending fatal signal.
*/
- rcu_read_lock();
+ guard(rcu)();
for_each_process(p) {
if (!process_shares_mm(p, mm))
continue;
@@ -982,7 +978,6 @@ static void __oom_kill_process(struct task_struct *victim, const char *message)
continue;
do_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_TGID);
}
- rcu_read_unlock();
if (can_oom_reap)
queue_oom_reaper(victim);
--
2.25.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] mm/oom_kill: simplify remaining RCU sections with guard(rcu)
2026-08-13 3:26 [PATCH] mm/oom_kill: simplify remaining RCU sections with guard(rcu) Ye Liu
@ 2026-08-13 8:49 ` Michal Hocko
2026-08-13 9:51 ` Ye Liu
0 siblings, 1 reply; 3+ messages in thread
From: Michal Hocko @ 2026-08-13 8:49 UTC (permalink / raw)
To: Ye Liu
Cc: Andrew Morton, Ye Liu, David Rientjes, Shakeel Butt, linux-mm,
linux-kernel
On Thu 13-08-26 11:26:33, Ye Liu wrote:
> From: Ye Liu <liuye@kylinos.cn>
>
> Replace the remaining manual rcu_read_lock()/rcu_read_unlock() pairs
> in oom_cpuset_eligible(), select_bad_process(), dump_tasks(),
> task_will_free_mem(), and __oom_kill_process() with guard(rcu)() for
> consistency and simpler control flow.
Could you use scoped_guard instead? While all these functions do not
perform anything pas the for loop this might change in the future and I
find it more obvious what the actual scope for the RCU is rather than
the full function one.
>
> Signed-off-by: Ye Liu <liuye@kylinos.cn>
> ---
> mm/oom_kill.c | 15 +++++----------
> 1 file changed, 5 insertions(+), 10 deletions(-)
>
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 4b5c70aaece4..8bbb5ca00bb6 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -94,7 +94,7 @@ static bool oom_cpuset_eligible(struct task_struct *start,
> bool ret = false;
> const nodemask_t *mask = oc->nodemask;
>
> - rcu_read_lock();
> + guard(rcu)();
> for_each_thread(start, tsk) {
> if (mask) {
> /*
> @@ -114,7 +114,6 @@ static bool oom_cpuset_eligible(struct task_struct *start,
> if (ret)
> break;
> }
> - rcu_read_unlock();
>
> return ret;
> }
> @@ -368,11 +367,10 @@ static void select_bad_process(struct oom_control *oc)
> else {
> struct task_struct *p;
>
> - rcu_read_lock();
> + guard(rcu)();
> for_each_process(p)
> if (oom_evaluate_task(p, oc))
> break;
> - rcu_read_unlock();
> }
> }
>
> @@ -430,14 +428,13 @@ static void dump_tasks(struct oom_control *oc)
> struct task_struct *p;
> int i = 0;
>
> - rcu_read_lock();
> + guard(rcu)();
> for_each_process(p) {
> /* Avoid potential softlockup warning */
> if ((++i & 1023) == 0)
> touch_softlockup_watchdog();
> dump_task(p, oc);
> }
> - rcu_read_unlock();
> }
> }
>
> @@ -894,7 +891,7 @@ static bool task_will_free_mem(struct task_struct *task)
> * are dying as well to make sure that a) nobody pins its mm and
> * b) the task is also reapable by the oom reaper.
> */
> - rcu_read_lock();
> + guard(rcu)();
> for_each_process(p) {
> if (!process_shares_mm(p, mm))
> continue;
> @@ -904,7 +901,6 @@ static bool task_will_free_mem(struct task_struct *task)
> if (!ret)
> break;
> }
> - rcu_read_unlock();
>
> return ret;
> }
> @@ -960,7 +956,7 @@ static void __oom_kill_process(struct task_struct *victim, const char *message)
> * That thread will now get access to memory reserves since it has a
> * pending fatal signal.
> */
> - rcu_read_lock();
> + guard(rcu)();
> for_each_process(p) {
> if (!process_shares_mm(p, mm))
> continue;
> @@ -982,7 +978,6 @@ static void __oom_kill_process(struct task_struct *victim, const char *message)
> continue;
> do_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_TGID);
> }
> - rcu_read_unlock();
>
> if (can_oom_reap)
> queue_oom_reaper(victim);
> --
> 2.25.1
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] mm/oom_kill: simplify remaining RCU sections with guard(rcu)
2026-08-13 8:49 ` Michal Hocko
@ 2026-08-13 9:51 ` Ye Liu
0 siblings, 0 replies; 3+ messages in thread
From: Ye Liu @ 2026-08-13 9:51 UTC (permalink / raw)
To: Michal Hocko
Cc: Andrew Morton, Ye Liu, David Rientjes, Shakeel Butt, linux-mm,
linux-kernel
在 2026/8/13 16:49, Michal Hocko 写道:
> On Thu 13-08-26 11:26:33, Ye Liu wrote:
>> From: Ye Liu <liuye@kylinos.cn>
>>
>> Replace the remaining manual rcu_read_lock()/rcu_read_unlock() pairs
>> in oom_cpuset_eligible(), select_bad_process(), dump_tasks(),
>> task_will_free_mem(), and __oom_kill_process() with guard(rcu)() for
>> consistency and simpler control flow.
>
> Could you use scoped_guard instead? While all these functions do not
> perform anything pas the for loop this might change in the future and I
> find it more obvious what the actual scope for the RCU is rather than
> the full function one.
>>
Thanks for the suggestion, I've updated to V2.
>> Signed-off-by: Ye Liu <liuye@kylinos.cn>
>> ---
>> mm/oom_kill.c | 15 +++++----------
>> 1 file changed, 5 insertions(+), 10 deletions(-)
>>
>> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
>> index 4b5c70aaece4..8bbb5ca00bb6 100644
>> --- a/mm/oom_kill.c
>> +++ b/mm/oom_kill.c
>> @@ -94,7 +94,7 @@ static bool oom_cpuset_eligible(struct task_struct *start,
>> bool ret = false;
>> const nodemask_t *mask = oc->nodemask;
>>
>> - rcu_read_lock();
>> + guard(rcu)();
>> for_each_thread(start, tsk) {
>> if (mask) {
>> /*
>> @@ -114,7 +114,6 @@ static bool oom_cpuset_eligible(struct task_struct *start,
>> if (ret)
>> break;
>> }
>> - rcu_read_unlock();
>>
>> return ret;
>> }
>> @@ -368,11 +367,10 @@ static void select_bad_process(struct oom_control *oc)
>> else {
>> struct task_struct *p;
>>
>> - rcu_read_lock();
>> + guard(rcu)();
>> for_each_process(p)
>> if (oom_evaluate_task(p, oc))
>> break;
>> - rcu_read_unlock();
>> }
>> }
>>
>> @@ -430,14 +428,13 @@ static void dump_tasks(struct oom_control *oc)
>> struct task_struct *p;
>> int i = 0;
>>
>> - rcu_read_lock();
>> + guard(rcu)();
>> for_each_process(p) {
>> /* Avoid potential softlockup warning */
>> if ((++i & 1023) == 0)
>> touch_softlockup_watchdog();
>> dump_task(p, oc);
>> }
>> - rcu_read_unlock();
>> }
>> }
>>
>> @@ -894,7 +891,7 @@ static bool task_will_free_mem(struct task_struct *task)
>> * are dying as well to make sure that a) nobody pins its mm and
>> * b) the task is also reapable by the oom reaper.
>> */
>> - rcu_read_lock();
>> + guard(rcu)();
>> for_each_process(p) {
>> if (!process_shares_mm(p, mm))
>> continue;
>> @@ -904,7 +901,6 @@ static bool task_will_free_mem(struct task_struct *task)
>> if (!ret)
>> break;
>> }
>> - rcu_read_unlock();
>>
>> return ret;
>> }
>> @@ -960,7 +956,7 @@ static void __oom_kill_process(struct task_struct *victim, const char *message)
>> * That thread will now get access to memory reserves since it has a
>> * pending fatal signal.
>> */
>> - rcu_read_lock();
>> + guard(rcu)();
>> for_each_process(p) {
>> if (!process_shares_mm(p, mm))
>> continue;
>> @@ -982,7 +978,6 @@ static void __oom_kill_process(struct task_struct *victim, const char *message)
>> continue;
>> do_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_TGID);
>> }
>> - rcu_read_unlock();
>>
>> if (can_oom_reap)
>> queue_oom_reaper(victim);
>> --
>> 2.25.1
>
--
Thanks,
Ye Liu
^ permalink raw reply [flat|nested] 3+ messages in thread
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2026-08-13 3:26 [PATCH] mm/oom_kill: simplify remaining RCU sections with guard(rcu) Ye Liu
2026-08-13 8:49 ` Michal Hocko
2026-08-13 9:51 ` Ye Liu
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