From: Oleg Nesterov <oleg@redhat.com>
To: chenqiwu <qiwuchen55@gmail.com>
Cc: Christian Brauner <christian.brauner@ubuntu.com>,
peterz@infradead.org, mingo@kernel.org, kernel-team@android.com,
linux-kernel@vger.kernel.org, chenqiwu@xiaomi.com
Subject: Re: [PATCH v2] kernel/exit: do panic earlier to get coredump if global init task exit
Date: Tue, 17 Dec 2019 15:25:15 +0100 [thread overview]
Message-ID: <20191217142515.GB23152@redhat.com> (raw)
In-Reply-To: <20191217105042.GA21784@cqw-OptiPlex-7050>
On 12/17, chenqiwu wrote:
>
> @@ -728,6 +724,15 @@ void __noreturn do_exit(long code)
> panic("Attempted to kill the idle task!");
>
> /*
> + * If all threads of global init have exited, do panic imeddiately
> + * to get the coredump to find any clue for init task in userspace.
> + */
> + if (unlikely(is_global_init(tsk) &&
> + (atomic_read(&tsk->signal->live) == 1)))
Well, I guess this will work in practice, but in theory this is racy.
Suppose that signal->live == 2 and both threads exit in parallel. They
both can see tsk->signal->live == 2 before atomic_dec_and_test().
If you are fine with this race I won't object, but please add a comment.
But why can't you simply do
--- x/kernel/exit.c
+++ x/kernel/exit.c
@@ -786,6 +786,8 @@ void __noreturn do_exit(long code)
acct_update_integrals(tsk);
group_dead = atomic_dec_and_test(&tsk->signal->live);
if (group_dead) {
+ if (unlikely(is_global_init(tsk)
+ panic(...);
#ifdef CONFIG_POSIX_TIMERS
hrtimer_cancel(&tsk->signal->real_timer);
exit_itimers(tsk->signal);
?
Oleg.
next prev parent reply other threads:[~2019-12-17 14:25 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-16 3:18 [PATCH v2] kernel/exit: do panic earlier to get coredump if global init task exit qiwuchen55
2019-12-16 10:27 ` Christian Brauner
2019-12-16 17:28 ` Oleg Nesterov
2019-12-16 17:44 ` Christian Brauner
2019-12-17 10:50 ` chenqiwu
2019-12-17 14:25 ` Oleg Nesterov [this message]
2019-12-17 14:56 ` chenqiwu
2019-12-17 15:23 ` Oleg Nesterov
2019-12-17 19:33 ` Peter Zijlstra
2019-12-18 8:08 ` chenqiwu
2019-12-17 14:14 ` Oleg Nesterov
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