linux-kernel - Re: [Bisected] 3.7-rc1 can't resume (still present in 3.9)

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Date:	Thu, 2 May 2013 20:32:30 +0000
From:	Jonas Heinrich <onny@...ject-insanity.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>, "H. Peter Anvin" <hpa@...or.com>
Cc:	len.brown@...el.com, pavel@....cz, tglx@...utronix.de,
	mingo@...hat.com, x86@...nel.org, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org,
	Jarkko Sakkinen <jarkko.sakkinen@...el.com>
Subject: Re: [Bisected] 3.7-rc1 can't resume (still present in 3.9)

On 05-02 02:45, Rafael J. Wysocki wrote:
> On Wednesday, May 01, 2013 11:55:10 AM H. Peter Anvin wrote:
> > On 05/01/2013 11:51 AM, Jonas Heinrich wrote:
> > > Well, you could give me instructions on how to debug this (I'll do 
> > > everything ;)) or I could ship you the Thinkpad T43. I guess this
> > > would worth the effort since this bug is somehow critical.
> > > 
> > > Best regards, Jonas
> > 
> > I'll put together a debug patch unless I can trick Rafael into doing
> > it first...
> 
> I'm afraid that code has changed quite a bit since I looked at it last time.
> [Jarkko Sakkinen seems to have worked on it lately, CCed.]
> 
> Jonas, I wonder what happens if you drop the first hunk of the patch (it just
> uses a different register, which shouldn't matter)?  Does it still help then?

Hello Rafel, first of all, thank you for helping me out :)
You're right, the patch still solves the suspend bug, after removing the first 
hunk of the patch and applying it (see attachement:
suspendfix_first_hunk_dropped.patch).

> 
> If so, there are still a few things you can do to it, e.g:
> (1) drop the
> 
> -       btl     $WAKEUP_BEHAVIOR_RESTORE_CR4, %edi
> -       jnc     1f
> 

Still works :) (used suspendfix_1.patch)

> lines,
> (2) drop the
> 
> -       btl     $WAKEUP_BEHAVIOR_RESTORE_EFER, %edi
> -       jnc     1f
> 
> lines,

Still works :) (used suspendfix_2.patch)

> (3) drop the
> 
> +       jecxz   1f
> 

Still works :) (used suspendfix_3.patch)

> line,
> (4) drop the
> 
> +       movl    %eax, %ecx
> +       orl     %edx, %ecx
> +       jz      1f
> 

At this point, the bug reoccurs (used suspendfix_4.patch)! 
But that doesn't mean these lines are the only critical, because the more
minimal patch

@@ -119,6 +119,9 @@
        jnc     1f
        movl    pmode_efer, %eax
        movl    pmode_efer + 4, %edx
+       movl    %eax, %ecx
+       orl     %edx, %ecx
+       jz      1f
        movl    $MSR_EFER, %ecx
        wrmsr
 1:


with removing this part

-       movl    pmode_cr4, %eax
-       movl    %eax, %cr4
+       movl    pmode_cr4, %ecx
+       movl    %ecx, %cr4

also doesn't fix the issue (see suspendfix_5.patch).

> lines and see what the minimal patch needed for things to work again is.
> 

So the most minimal working patch is suspendfix_3.patch.

> Thanks,
> Rafael

Thank you and best regards,
Jonas

> 
> 
> -- 
> I speak only for myself.
> Rafael J. Wysocki, Intel Open Source Technology Center.

View attachment "suspendfix_first_hunk_dropped.patch" of type "text/plain" (545 bytes)

View attachment "suspendfix_1.patch" of type "text/plain" (504 bytes)

View attachment "suspendfix_2.patch" of type "text/plain" (504 bytes)

View attachment "suspendfix_3.patch" of type "text/plain" (497 bytes)

View attachment "suspendfix_4.patch" of type "text/plain" (361 bytes)

View attachment "suspendfix_5.patch" of type "text/plain" (312 bytes)

Content of type "application/pgp-signature" skipped