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

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Date:   Mon, 26 Sep 2022 15:20:38 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Shuai Xue <xueshuai@...ux.alibaba.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>
CC:     Len Brown <lenb@...nel.org>, James Morse <james.morse@....com>,
        "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

>>
>> -               if (task_work_pending && current->mm != &init_mm) {
>> +               if (task_work_pending && current->mm) {
>>                         estatus_node->task_work.func = ghes_kick_task_work;
>>                         estatus_node->task_work_cpu = smp_processor_id();
>>                         ret = task_work_add(current, &estatus_node->task_work,

It seems that you are getting errors reported while running kernel threads. This fix avoids
pointlessly adding "task_work" that will never be processed because kernel threads never
return to user mode.

But maybe something else needs to be done? The code was, and with this fix still is,
taking no action for the error. That doesn't seem right.

Are you injecting errors to create this scenario? What does your test do?

-Tony