[PATCH v2] sched: clarify ptrace's effect on task_struct->parent

[Ziran Zhang <zhangcoder@yeah.net>]

The current comment for the parent field does not explain that it can be
temporarily replaced by the tracer when the task is being ptraced.

This can lead to confusion, so clarify the comment to document this
important behavior.

No functional change.

Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Ziran Zhang <zhangcoder@yeah.net>
---
Changes in v2:
- Use Oleg's minimal wording suggestion to adjust comment.

 include/linux/sched.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 705970d07..8aad8a8ef 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1093,7 +1093,7 @@ struct task_struct {
 	/* Real parent process: */
 	struct task_struct __rcu	*real_parent;
 
-	/* Recipient of SIGCHLD, wait4() reports: */
+	/* Recipient of SIGCHLD, wait4() reports: ->real_parent or ptracer */
 	struct task_struct __rcu	*parent;
 
 	/*
-- 
2.51.0