linux-kernel - [RFC] decrease tsk->signal->live before profile_task

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Date:   Thu, 28 May 2020 12:09:56 +0800
From:   liuchao <liuchao173@...wei.com>
To:     <mingo@...nel.org>, <tglx@...utronix.de>
CC:     <linux-kernel@...r.kernel.org>, <hushiyuan@...wei.com>,
        <hewenliang4@...wei.com>, liuchao <liuchao173@...wei.com>
Subject: [RFC] decrease tsk->signal->live before profile_task_exit

I want to dermine which thread is the last one to enter
do_exit in profile_task_exit. But when a lot of threads
exit, tsk->signal->live is not correct since it decrease
after profile_task_exit.

Signed-off-by: liuchao <liuchao173@...wei.com>
---
 kernel/exit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/exit.c b/kernel/exit.c
index ce2a75bc0ade..1693764bc356 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -708,6 +708,7 @@ void __noreturn do_exit(long code)
 	struct task_struct *tsk = current;
 	int group_dead;
 
+	group_dead = atomic_dec_and_test(&tsk->signal->live);
 	profile_task_exit(tsk);
 	kcov_task_exit(tsk);
 
@@ -755,7 +756,6 @@ void __noreturn do_exit(long code)
 	if (tsk->mm)
 		sync_mm_rss(tsk->mm);
 	acct_update_integrals(tsk);
-	group_dead = atomic_dec_and_test(&tsk->signal->live);
 	if (group_dead) {
 		/*
 		 * If the last thread of global init has exited, panic
-- 
2.19.1