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Date:   Fri, 11 Feb 2022 15:42:38 -0800
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Subject: Re: [PATCH 2/8] kernel/fork: Duplicate task_struct before stack
 allocation.
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To:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org
Cc:     Ben Segall <bsegall@google.com>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Ingo Molnar <mingo@redhat.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vincent Guittot <vincent.guittot@linaro.org>
References: <20220125152652.1963111-1-bigeasy@linutronix.de>
 <20220125152652.1963111-3-bigeasy@linutronix.de>
From:   Andy Lutomirski <luto@kernel.org>
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On 1/25/22 07:26, Sebastian Andrzej Siewior wrote:
> alloc_thread_stack_node() already populates the task_struct::stack
> member except on IA64. The stack pointer is saved and populated again
> because IA64 needs it and arch_dup_task_struct() overwrites it.

I understand the problem, I think.

> 
> Allocate thread's stack after task_struct has been duplicated as a
> preparation.
> 

But I don't understand this.  How does this patch relate to the problem?

Also, you appear to be missing a change to the free_stack and free_tsk 
code at the end of dup_task_struct().