linux-kernel - Re: 2.6.25-rc6 hangs at resume after suspend to RAM on Mac mini Core Duo

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Message-Id: <20080401200618.7284DCC224@adsl-69-226-248-13.dsl.pltn13.pacbell.net>
Date:	Tue, 01 Apr 2008 13:06:18 -0700
From:	David Brownell <david-b@...bell.net>
To:	tino.keitel@....de, pavel@....cz, linux-usb@...r.kernel.org
Cc:	sonne@....de, rjw@...k.pl, linux-kernel@...r.kernel.org,
	lenb@...nel.org, akpm@...ux-foundation.org
Subject: Re: 2.6.25-rc6 hangs at resume after suspend to RAM on Mac mini Core 
 Duo

> git-bisect revealed this:
>
> $ git bisect good
> e82cc1288fa57857c6af8c57f3d07096d4bcd9d9 is first bad commit
> commit e82cc1288fa57857c6af8c57f3d07096d4bcd9d9
> Author: David Brownell <david-b@...bell.net>
> Date:   Fri Mar 7 13:49:42 2008 -0800
>
>     USB: fix ehci unlink regressions

Most curious.  Based on what I read earlier, I was wondering about
the handling of the unlink watchdog during a known-dodgey path.

Specifically:

>     The recent EHCI driver update to split the IAA watchdog timer out from
>     the other timers made several things work better, but not everything;
>     and it created a couple new issues in bugzilla.  Ergo this patch:
>     
>       - Handle a should-be-rare SMP race between the watchdog firing
>         and (very late) IAA interrupts;
>     
>       - Remove a shouldn't-have-been-added WARN_ON() test;
>     
>       - Guard against one observed OOPS;
>     
>       - If this watchdog fires during clean HC shutdown, it should act
>         as a NOP instead of interfering with the shutdown sequence;

This "fires during a clean shutdown" path.  If there's any way this
patch would affect resume handling, that's where I'd expect it to
kick in.  Virtually nothing else *could* cause problems there.

If you'd like to experiment, modify the "if (...)" at the top of the
ehci_iaa_watchdog() function and make it just check to see if there's
an entry being reclaimed ... comment out the HC_IS_RUNNING() check.


>       - Guard against silicon errata hypothesized by some vendors:
>           * IAA status latch broken, but IAAD cleared OK;
>           * IAAD wasn't cleared when IAA status got reported;

FWIW the former has been confirmed as existing on some current AMD/ATI
chipsets (SB600 and SB700 are the numbers that come to mind).


>     The WARN_ON is in bugzilla as 10168; the OOPS as 10078; these are
>     both regressions.
>     
>     Signed-off-by: David Brownell <dbrownell@...rs.sourceforge.net>
>     Tested-by: Gordon Farquharson <gordonfarquharson@...il.com>
>     Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

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