linux-kernel - Re: 2.6.27-rc4: 90% system time because of khubd, unable to reboot

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Message-Id: <200808222157.29299.arvidjaar@mail.ru>
Date:	Fri, 22 Aug 2008 21:57:22 +0400
From:	Andrey Borzenkov <arvidjaar@...l.ru>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	linux-usb@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"Greg Kroah-Hartman" <gregkh@...e.de>
Subject: Re: 2.6.27-rc4: 90% system time because of khubd, unable to reboot

On Friday 22 August 2008, Alan Stern wrote:
> On Fri, 22 Aug 2008, Andrey Borzenkov wrote:
> 
> > > > reverting 38b375d9610e2467cb793a84d17c6f65e44cdb39 fixed it
> > > > 
> > > 
> > > ... that is:
> > > 
> > > commit 38b375d9610e2467cb793a84d17c6f65e44cdb39
> > > Author: Alan Stern <stern@...land.harvard.edu>
> > > Date:   Mon Jul 21 09:56:26 2008 -0400
> > > 
> > >     USB: OHCI: fix system hang caused by earlier patch
> > > 
> > >     Signed-off-by: Alan Stern <stern@...land.harvard.edu>
> > >     Tested by: Andrey Borzenkov <arvidjaar@...l.ru>
> > >     Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
> > > 
> > > so it apparently used to work for you at that time.  What gives?
> > > 
> > 
> > Well, you should not commit a fix without commiting code that has been
> > fixed first :)
> 
> Actually the code to be fixed _was_ committed first -- but then it was 
> reverted before the fix was accepted, so the fix was merged without it.
> 
> My advice is not to worry about it.  That code has been sent once again
> to Linus -- it's not merged yet but presumably it will be soon.  
> Certainly before 2.6.27-rc5 appears.
> 
> On the other hand, I still have to wonder how the fix could have caused
> your problem without the original patch in place.  The fix itself
> should have been totally innocuous.
> 

It looks even funnier. Right now I am running with commits
38b375d9610e2467cb793a84d17c6f65e44cdb39 *and*
e872154921a6b5256a3c412dd69158ac0b135176 reverted. I.e. this should be
the state which hopelessly failed in 2.6.26-rc. It seems to be doing
quite well now in 2.6.27-rc.

"git revert e872154921a6b5256a3c412dd69158ac0b135176" gives me this
one liner patch:

commit f3cf9ad86ee76077d1c6be9af7d197aa13ccdff9
Author: Andrey Borzenkov <arvidjaar@...l.ru>
Date:   Fri Aug 22 21:15:26 2008 +0400

    Revert "USB: don't explicitly reenable root-hub status interrupts"

    This reverts commit e872154921a6b5256a3c412dd69158ac0b135176.

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 107e1d2..d30f822 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -3086,6 +3086,11 @@ static void hub_events(void)
                if (!hdev->parent && !hub->busy_bits[0])
                        usb_enable_root_hub_irq(hdev->bus);

+               /* If this is a root hub, tell the HCD it's okay to
+                * re-enable port-change interrupts now. */
+               if (!hdev->parent && !hub->busy_bits[0])
+                       usb_enable_root_hub_irq(hdev->bus);
+
 loop_autopm:
                /* Allow autosuspend if we're not going to run again */
                if (list_empty(&hub->event_list))

Either my git tree is completely botched or most parts were already reverted
before.

So the problem seems to have cured by itself between 2.6.26 and 2.6.27?  

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