linux-kernel - Re: [PATCH] acpi: scan: Fix a possible data race in acpi_scan_hotplug

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Message-ID: <CAJZ5v0gT2aHE5xXgCYXD1DRkMFJZeHJSg+zVHnxsJ69-d+qrxQ@mail.gmail.com>
Date:   Wed, 9 May 2018 09:53:56 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Jia-Ju Bai <baijiaju1990@...il.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] acpi: scan: Fix a possible data race in acpi_scan_hotplug_enabled

On Wed, May 9, 2018 at 5:17 AM, Jia-Ju Bai <baijiaju1990@...il.com> wrote:
>
>
> On 2018/5/9 4:17, Rafael J. Wysocki wrote:
>>
>> On Tue, May 8, 2018 at 5:08 AM, Jia-Ju Bai <baijiaju1990@...il.com> wrote:
>>>
>>> The write operation to "hotplug->enabled" is protected by
>>> the lock on line 1760, but the read operation to
>>> this data on line 1755 is not protected by the lock.
>>> Thus, there may exist a data race for "hotplug->enabled".
>>
>> Either it does exist, or it doesn't.
>>
>> If it exists, it needs to be fixed.  If it doesn't exist, nothing
>> needs to be done.
>>
>> Which is the case?
>
>
> I only read the code and find this possible data race.
> It is not found in real driver execution.
> I am not sure of it, so I use "may" and "possible" here.

It looks like you are not actually sure what you are doing then.