[PATCH] mm/oom_kill: simplify remaining RCU sections with guard(rcu)

[Ye Liu <ye.liu@linux.dev>]

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