[PATCH 1/3] workqueue: use rcu_dereference_sched() in workqueue_congested()

[Breno Leitao]

workqueue_congested() fetches the pwq out of wq->cpu_pwq with a plain
load, so sparse complains about the dropped __rcu:

  kernel/workqueue.c:6304:13: sparse: incorrect type in assignment (different address spaces) @@     expected struct pool_workqueue *pwq @@     got struct pool_workqueue [noderef] __rcu * @@

A pwq is released with kfree_rcu() and the read is protected by the
surrounding preempt_disable(), which is what
commit fd5081f4ef33 ("workqueue: Remove redundant rcu_read_lock/unlock() in
workqueue_congested()") relied on when it dropped the rcu_read_lock()
here.

Use the rcu_dereference_sched() helper to make that explicit.

Reported-by: kernel test robot <lkp@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-kbuild-all/202608120931.tvTzq1gD-lkp@xxxxxxxxx/
Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>
---
 kernel/workqueue.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index de888e043d115..1748ef5541a26 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -6317,7 +6317,7 @@ bool workqueue_congested(int cpu, struct workqueue_struct *wq)
 	if (cpu == WORK_CPU_UNBOUND)
 		cpu = smp_processor_id();
 
-	pwq = *per_cpu_ptr(wq->cpu_pwq, cpu);
+	pwq = rcu_dereference_sched(*per_cpu_ptr(wq->cpu_pwq, cpu));
 	ret = !list_empty(&pwq->inactive_works);
 
 	preempt_enable();

-- 
2.53.0-Meta