linux-kernel - RE: [PATCH v2] ACPI: APEI: do not add task_work to kernel thread to avoid memory leak

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Date:   Thu, 29 Sep 2022 20:52:02 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Shuai Xue <xueshuai@...ux.alibaba.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        James Morse <james.morse@....com>
CC:     Len Brown <lenb@...nel.org>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        HORIGUCHI NAOYA(堀口 直也) 
        <naoya.horiguchi@....com>,
        "linmiaohe@...wei.com" <linmiaohe@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stable <stable@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        "cuibixuan@...ux.alibaba.com" <cuibixuan@...ux.alibaba.com>,
        "baolin.wang@...ux.alibaba.com" <baolin.wang@...ux.alibaba.com>,
        "zhuo.song@...ux.alibaba.com" <zhuo.song@...ux.alibaba.com>
Subject: RE: [PATCH v2] ACPI: APEI: do not add task_work to kernel thread to
 avoid memory leak

Thanks for your patient explanations.

> STEP2: In IRQ context, ghes_proc_in_irq() queues memory failure work on current CPU
> in workqueue and add task work to sync with the workqueue.

Why is there a difference if the interrupted task was a user task vs. a kernel thread?

It seems arbitrary. If the error can be handled in the kernel thread case without
a task_work_add() to the current process, can't all errors be handled this way?

The current thread likely has nothing to do with the error. Just a matter of chance
on what is running when the NMI is delivered, right?

-Tony