linux-kernel - [PATCH v1 3/4] exec: Remove BUG_ON(has_group_leader

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Message-ID: <87zhav5lb8.fsf_-_@x220.int.ebiederm.org>
Date:   Tue, 28 Apr 2020 16:53:31 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Oleg Nesterov <oleg@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH v1 3/4] exec: Remove BUG_ON(has_group_leader_pid)

With the introduction of exchange_tids thread_group_leader and
has_group_leader_pid have become equivalent.  Further at this point in the
code a thread group has exactly two threads, the previous thread_group_leader
that is waiting to be reaped and tsk.  So we know it is impossible for tsk to
be the thread_group_leader.

This is also the last user of has_group_leader_pid so removing this check
will allow has_group_leader_pid to be removed.

So remove the "BUG_ON(has_group_leader_pid)" that will never fire.

Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 fs/exec.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/fs/exec.c b/fs/exec.c
index 9b60f927afd7..6ab1c19d84fa 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1176,7 +1176,6 @@ static int de_thread(struct task_struct *tsk)
 		tsk->start_boottime = leader->start_boottime;

 		BUG_ON(!same_thread_group(leader, tsk));
-		BUG_ON(has_group_leader_pid(tsk));
 		/*
 		 * An exec() starts a new thread group with the
 		 * TGID of the previous thread group. Rehash the
-- 
2.20.1