linux-kernel - Re: [PATCH] Fix resume on x86-32 machines

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Date:   Mon, 11 Dec 2017 11:25:25 +0200
From:   Jarkko Nikula <jarkko.nikula@...ux.intel.com>
To:     Pavel Machek <pavel@....cz>, Andy Lutomirski <luto@...capital.net>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Andrew Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [PATCH] Fix resume on x86-32 machines

On 12/11/2017 12:20 AM, Pavel Machek wrote:
> On Sun 2017-12-10 13:58:23, Andy Lutomirski wrote:
>>> On Dec 10, 2017, at 1:38 PM, Pavel Machek <pavel@....cz> wrote:
>>>
>>>
>>> After 4.15-rc2, suspend stopped working on Thinkpad X60. 5b06bbc
>>> (unintentionally?) reordered stuff with respect to
>>> fix_processor_context() on 32-bit and 64-bit. We undo that change on
>>> 32-bit.
>>>
>>
>> Can you explain what was wrong with the reordering?  Your patch certainly *looks* incorrect.
>>
> 
> No, I can't, sorry.
> 
>> I'm guessing that the real issue is that 32-bit needs %fs restored
>>   early for TLS.
> 
> Maybe. I can test patches...
> 
> I don't think it would be good idea to revert
> 5b06bbcfc2c621da3009da8decb7511500c293ed, but since it introduced
> regression in -rc2, I believe we should fix the regression now, and
> then we can try to provide cleaner solution.
> 
I can confirm Pavel's findings. Commit 5b06bbcfc2c6 ("x86/power: Fix 
some ordering bugs in __restore_processor_context()") broke the 
suspend/resume on 32-bit kernel.

v4.15-rc3 works either by reverting the commit or by Pavel's patch. 
Fortunately Pavel's patch still keeps the 64-bit suspend/resume ok.

-- 
Jarkko