[PATCH 1/1] timer: Warn about schedule_timeout() called for tasks in TASK_RUNNING state

[Alexander Popov]

When we were preparing the patch 6dcd5d7a7a29c1e, we made a mistake noticed
by Linus: schedule_timeout() was called without setting the task state to
anything particular. It calls the scheduler, but doesn't delay anything,
because the task stays runnable. That happens because sched_submit_work()
does nothing for tasks in TASK_RUNNING state.

Let's add a WARN_ONCE() under CONFIG_SCHED_DEBUG to detect such kernel
API misuse.

Signed-off-by: Alexander Popov <alex.popov@xxxxxxxxx>
---
 kernel/time/timer.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 4820823515e9..52ad2d6ce352 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1887,6 +1887,11 @@ signed long __sched schedule_timeout(signed long timeout)
 		}
 	}
 
+#ifdef CONFIG_SCHED_DEBUG
+	WARN_ONCE(current->state == TASK_RUNNING,
+			"schedule_timeout for TASK_RUNNING\n");
+#endif
+
 	expire = timeout + jiffies;
 
 	timer.task = current;
-- 
2.24.1