1 files changed, 11 insertions, 0 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 38c8654aaa96..49e617fa0f66 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -121,6 +121,17 @@ extern unsigned long nr_iowait(void);
 #define set_task_state(tsk, state_value)                \
         set_mb((tsk)->state, (state_value))
 
+/*
+ * set_current_state() includes a barrier so that the write of current->state
+ * is correctly serialised wrt the caller's subsequent test of whether to
+ * actually sleep:
+ *
+ *      set_current_state(TASK_UNINTERRUPTIBLE);
+ *      if (do_i_need_to_sleep())
+ *              schedule();
+ *
+ * If the caller does not need such serialisation then use __set_current_state()
+ */
 #define __set_current_state(state_value)                        \
         do { current->state = (state_value); } while (0)
 #define set_current_state(state_value)          \