[PATCH] completion: Use lockdep_assert_RT_in_threaded_ctx() in complete_all()

[Sebastian Siewior <bigeasy@xxxxxxxxxxxxx>]

The warning was intended to spot complete_all() users from hardirq
context on PREEMPT_RT. The warning as-is will also trigger in interrupt
handlers, which are threaded on PREEMPT_RT, which was not intended.

Use lockdep_assert_RT_in_threaded_ctx() which triggers in non-preemptive
context on PREEMPT_RT.

Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Reported-by: kernel test robot <rong.a.chen@xxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
 include/linux/lockdep.h   | 15 +++++++++++++++
 kernel/sched/completion.c |  2 +-
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 425b4ceb7cd07..206774ac69460 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -711,6 +711,21 @@ do {									\
 # define lockdep_assert_in_irq() do { } while (0)
 #endif
 
+#ifdef CONFIG_PROVE_RAW_LOCK_NESTING
+
+# define lockdep_assert_RT_in_threaded_ctx() do {			\
+		WARN_ONCE(debug_locks && !current->lockdep_recursion &&	\
+			  current->hardirq_context &&			\
+			  !(current->hardirq_threaded || current->irq_config),	\
+			  "Not in threaded context on PREEMPT_RT as expected\n");	\
+} while (0)
+
+#else
+
+# define lockdep_assert_RT_in_threaded_ctx() do { } while (0)
+
+#endif
+
 #ifdef CONFIG_LOCKDEP
 void lockdep_rcu_suspicious(const char *file, const int line, const char *s);
 #else
diff --git a/kernel/sched/completion.c b/kernel/sched/completion.c
index f15e96164ff1e..a778554f9dad7 100644
--- a/kernel/sched/completion.c
+++ b/kernel/sched/completion.c
@@ -58,7 +58,7 @@ void complete_all(struct completion *x)
 {
 	unsigned long flags;
 
-	WARN_ON(irqs_disabled());
+	lockdep_assert_RT_in_threaded_ctx();
 
 	raw_spin_lock_irqsave(&x->wait.lock, flags);
 	x->done = UINT_MAX;
-- 
2.26.0.rc2