From e34a35ee1f52312af130b5ebd42fa28313fc6149 Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@redhat.com>
Date: Sat, 26 Aug 2023 13:14:06 +0200
Subject: [PATCH] change thread_group_empty() to use task_struct->thread_node
Patch series "kill task_struct->thread_group".
This patch (of 2):
It could use list_is_singular() but this way it is cheaper. Plus the
thread_group_leader() check makes it clear that thread_group_empty() can
only return true if p is a group leader. This was not immediately obvious
before this patch.
task_struct->thread_group no longer has users, it can die.
Link: https://lkml.kernel.org/r/20230826111200.GA22982@redhat.com
Link: https://lkml.kernel.org/r/20230826111406.GA23238@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
include/linux/sched/signal.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
index cffc882d367f5..d7fa3ca2fa532 100644
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -733,7 +733,8 @@ static inline struct task_struct *next_thread(struct task_struct *p)
static inline int thread_group_empty(struct task_struct *p)
{
- return list_empty(&p->thread_group);
+ return thread_group_leader(p) &&
+ list_is_last(&p->thread_node, &p->signal->thread_head);
}
#define delay_group_leader(p) \
--
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