Re: [PATCH v2 5/8] kernel: convert process/thread iterators to for_each_*_rculock

On Mon, Sep 07, 2026 at 11:53:51AM -0400, Gregory Price wrote:

On Mon, Sep 07, 2026 at 04:13:31PM +0800, Ye Liu wrote:

quoted

From: Ye Liu <liuye@kylinos.cn>

Replace the manual rcu_read_lock()/rcu_read_unlock() and guard(rcu)
pairs combined with for_each_process(), for_each_thread() and
for_each_process_thread() loops across kernel/ with the
for_each_*_rculock() macros, which scope the RCU read lock to the
loop body via scoped_guard(rcu).

No functional change.

Signed-off-by: Ye Liu <liuye@kylinos.cn>
Acked-by: Michal Hocko <mhocko@suse.com>

Question below

quoted

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;

... snip ...

quoted

- unlock:
-	rcu_read_unlock();
-
+out:
 	if (!this_round_count)
 		return;
 

The sunken rcu_read_lock()/unlock() + scoped_guard usage makes this goto
at a minimum very confusing, if not actually broken.

You can use goto to exit a scope, that's fine. Using goto to enter a
scope is not (clang will error on that).

Just don't use computed goto, that goes sideways real quick.