[PATCH] padata: use different lock_class_key for padata_list lock

[Tetsuo Handa]

syzbot is reporting possibility of deadlock due to calling spin_lock_init()
in __padata_list_init() from both padata_init_reorder_list() and
padata_init_squeues(). This is a false positive, for reorder->lock is never
the same as squeue->serial.lock.

Reported-by: syzbot+bd936ccd4339cea66e6b@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=bd936ccd4339cea66e6b
Suggested-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
 kernel/padata.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/padata.c b/kernel/padata.c
index f4def028c48c..465d25020e1e 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -529,12 +529,14 @@ static void padata_init_squeues(struct parallel_data *pd)
 /* Initialize per-CPU reorder lists */
 static void padata_init_reorder_list(struct parallel_data *pd)
 {
+	static struct lock_class_key padata_list_key;
 	int cpu;
 	struct padata_list *list;
 
 	for_each_cpu(cpu, pd->cpumask.pcpu) {
 		list = per_cpu_ptr(pd->reorder_list, cpu);
 		__padata_list_init(list);
+		lockdep_set_class(&list->lock, &padata_list_key);
 	}
 }
 
-- 
2.47.3