[PATCH v3 07/15] hung_task: convert process/thread iterators to for_each_*_rculock

[Ye Liu]

From: Ye Liu <liuye at kylinos.cn>

Replace the manual rcu_read_lock()/rcu_read_unlock() pair combined
with for_each_process_thread() loop in kernel/hung_task.c with
for_each_process_thread_rculock(), which scopes the RCU read lock
to the loop body via scoped_guard(rcu).

No functional change.

Signed-off-by: Ye Liu <liuye at kylinos.cn>
Acked-by: Michal Hocko <mhocko at suse.com>
Reviewed-by: SJ Park <sj at kernel.org>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs at kernel.org>
Reviewed-by: Oleg Nesterov <oleg at redhat.com>
---
Changes in v3:
  - Split from kernel/ patch in v2 (Peter Zijlstra, Steven Rostedt)

Changes in v2:
  - Rename *_rcu to *_rculock
  - Rename stale 'unlock:' label to 'out:' in hung_task.c (Günther Noack)
 kernel/hung_task.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index 6fcc94ce4ca9..73a5ad3be9a8 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -315,13 +315,12 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
 		return;
 
 	this_round_count = 0;
-	rcu_read_lock();
-	for_each_process_thread(g, t) {
+	for_each_process_thread_rculock(g, t) {
 		if (!max_count--)
-			goto unlock;
+			goto out;
 		if (time_after(jiffies, last_break + HUNG_TASK_LOCK_BREAK)) {
 			if (!rcu_lock_break(g, t))
-				goto unlock;
+				goto out;
 			last_break = jiffies;
 		}
 
@@ -337,9 +336,7 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
 			hung_task_info(t, timeout, this_round_count);
 		}
 	}
- unlock:
-	rcu_read_unlock();
-
+out:
 	if (!this_round_count)
 		return;
 
-- 
2.25.1