linux-kernel - Re: [PATCH v3] kernel/exit: do panic earlier to get coredump if global init task exit

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Message-ID: <20191219104223.xvk6ppfogoxrgmw6@wittgenstein>
Date:   Thu, 19 Dec 2019 11:42:24 +0100
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     qiwuchen55@...il.com
Cc:     peterz@...radead.org, mingo@...nel.org, oleg@...hat.com,
        prsood@...eaurora.org, kernel-team@...roid.com,
        linux-kernel@...r.kernel.org, chenqiwu@...omi.com
Subject: Re: [PATCH v3] kernel/exit: do panic earlier to get coredump if
 global init task exit

On Thu, Dec 19, 2019 at 02:29:53PM +0800, qiwuchen55@...il.com wrote:
> From: chenqiwu <chenqiwu@...omi.com>
> 
> When global init task get a chance to be killed, panic will happen in
> later calling steps by do_exit()->exit_notify()->forget_original_parent()
> ->find_child_reaper() if all init threads have exited.
> 
> However, it's hard to extract the coredump of init task from a kernel
> crashdump, since exit_mm() has released its mm before panic. In order
> to get the backtrace of init task in userspace, it's better to do panic
> earlier at the beginning of exitting route.
> 
> It's worth noting that we must take case of a multi-threaded init exitting
> issue. We need the test for is_global_init() && group_dead to ensure that
> it is all threads exiting and not just the current thread.
> 
> Signed-off-by: chenqiwu <chenqiwu@...omi.com>

Acked-by: Christian Brauner <christian.brauner@...ntu.com>