mm: Add comment explaining task state setting in bdi_forker_thread()

CC: Wu Fengguang <[email protected]>
CC: Andrew Morton <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

Author: jankara

mm/backing-dev.c

@@ -401,6 +401,13 @@ static int bdi_forker_thread(void *ptr)
 		}
 
 		spin_lock_bh(&bdi_lock);
+		/*
+		 * In the following loop we are going to check whether we have
+		 * some work to do without any synchronization with tasks
+		 * waking us up to do work for them. So we have to set task
+		 * state already here so that we don't miss wakeups coming
+		 * after we verify some condition.
+		 */
 		set_current_state(TASK_INTERRUPTIBLE);
 
 		list_for_each_entry(bdi, &bdi_list, bdi_list) {