Re: Linux 4.15-rc2: Regression in resume from ACPI S3

From: Pavel Machek <pavel@ucw.cz>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Zhang Rui <rui.zhang@intel.com>,
	Andrew Lutomirski <luto@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Jarkko Nikula <jarkko.nikula@linux.intel.com>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	the arch/x86 maintainers <x86@kernel.org>
Subject: Re: Linux 4.15-rc2: Regression in resume from ACPI S3
Date: Sun, 10 Dec 2017 22:35:18 +0100	[thread overview]
Message-ID: <20171210213516.GA5096@amd> (raw)
In-Reply-To: <CA+55aFwK96Eryb2PMoeaLxPSu4srGQakh=jO646Wqv9advLp0A@mail.gmail.com>

[-- Attachment #1: Type: text/plain, Size: 1760 bytes --]

On Sun 2017-12-10 13:28:50, Linus Torvalds wrote:
> On Sun, Dec 10, 2017 at 12:43 PM, Pavel Machek <pavel@ucw.cz> wrote:
> >
> > For the record... this should fix it. Tested on x60. More tests pending.
> 
> This can't be right.
> 
> At the very least, now the comment is wrong. And the comment does seem
> relevant for 32-bit too:

Well, take a look at orignal patch. I'm reverting 32-bit code to
v4.15-rc1 version, while keeping 64-bit code at v4.15-rc3
version. Yes, my brain hurts from looking at the code :-(.

In the meantime, I did short test on 64-bit machine. No ill effect observed.

Hmm. Aha. Yes, the comment is wrong... as it was in wrong in -rc1.

> > -       fix_processor_context();
> > -
> >         /*
> >          * Restore segment registers.  This happens after restoring the GDT
> >          * and LDT, which happen in fix_processor_context().
> 
> Notice? You've moved down the 32-bit fix_processor_context() call to
> after the loadsegment() calls, which smells wrong.

Yeah, I did. There's where it was in v4.15-rc1, and that's what ws
working for me. 

> That said, this *all* smells wrong. Why is there a special
> fix_processor_context() function at all with different 32-bit and
> 64-bit behavior? This code is all written to be maximally confusing.
> 
> I think this could do with some re-org to make it more logical. That
> "some random things done in fix_processor_context(), other random
> things done directly in __restore_processor_state()" makes no sense at
> all to me. There's no logic to what is done where.

I have to agree.
									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 181 bytes --]