linux-kernel - Re: [PATCH 4.14 05/69] x86/power: Make restore_processor

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Date:   Tue, 16 Apr 2019 13:56:44 +0200
From:   Pavel Machek <pavel@...x.de>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Pavel Machek <pavel@...x.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>,
        Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bpetkov@...e.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Zhang Rui <rui.zhang@...el.com>,
        Ingo Molnar <mingo@...nel.org>,
        Sasha Levin <sashal@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 4.14 05/69] x86/power: Make restore_processor_context()
 sane

On Mon 2019-04-15 13:18:56, Andy Lutomirski wrote:
> On Mon, Apr 15, 2019 at 1:04 PM Pavel Machek <pavel@...x.de> wrote:
> >
> > On Mon 2019-04-15 20:58:23, Greg Kroah-Hartman wrote:
> > > [ Upstream commit 7ee18d677989e99635027cee04c878950e0752b9 ]
> > >
> > > My previous attempt to fix a couple of bugs in __restore_processor_context():
> > >
> > >   5b06bbcfc2c6 ("x86/power: Fix some ordering bugs in __restore_processor_context()")
> > >
> > > ... introduced yet another bug, breaking suspend-resume.
> > >
> > > Rather than trying to come up with a minimal fix, let's try to clean it up
> > > for real.  This patch fixes quite a few things:
> >
> > 5b06bbcfc2c6 fixed theoretical bug; rather than porting it to stable
> > than fixing it up, it would be better not to port it to stable in the
> > first place or simply revert it there.
> 
> Are you sure about that?  The bug was reported by real users who had
> their systems really crash:
> 
> https://lore.kernel.org/lkml/?q=0fede9f9-88b0-a6e7-1027-dfb2019b8ef2%40linux.intel.com
> 
> https://lore.kernel.org/lkml/CA+55aFwsMuHUBQz5kDNwRf17JnasXMWjvmLq5qXGH-694yeq1w@mail.gmail.com/
> 
> And we had a report that the bug got backported:
> 
> https://lore.kernel.org/stable/20190407160005.djiw4reapwvbxmgo@debian/
> 
> And if we're going to backport some of the fix, we should definitely
> backport the whole set to avoid having the -stable kernels be in a
> state that was never in any released kernel.

I agree it should be all or nothing. And I may have been slightly
confused.

Anyway: 5b06bbcfc2c6 is fix for ca37e57bbe0cf, and that one is for
"mostly harmless warning" (quoting changelog). ca37e57bbe0cf is not
present in 4.4.178, I believe best solution is not to add that one in
the first place, so we don't have to fix it up.
								Pavel

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