Date:	Wed, 18 Aug 2010 03:25:17 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	trapdoor6@...il.com
Cc:	LKML <linux-kernel@...r.kernel.org>, arnd@...db.de,
	trapDoor <trapdoor6@...glemail.com>,
	Jiri Kosina <jkosina@...e.cz>
Subject: Re: [REGRESSION, bisected] 2.6.36-rc1 - suspend issues

On Tuesday, August 17, 2010, trapDoor wrote:
> Hello,
> The merge window is closed so it's time to hunt for bugs. I've got
> one, please find details below.
> -----------------------
> 
> Working kernels: from 2.6.35 - to 2.6.35.2
> Non working kernels: from (at least) 2.6.35-git2 - to 2.6.36-rc1
> -----------------------
> 
> Description of the problem(s):
> 
> 1. First of all I confirm that the problem is consistent: suspend
> works well every time on the 'good' kernels and it newer works (with
> the symptoms) on any of the 'bad' kernels. I've tested it several
> times on a couple of 'good' and 'bad' kernels to make sure it's not
> some random issue.
> 
> 2. On a bad kernel, this is what happens when I try to switch to suspend mode:
> - screen goes blank ['No signal detected !'] - that's OK :)
> - either the CPU fan or PSU fan or both are still running and they
> won't stop (left it for about 30 min. once)
> - the power light is on and still, where in suspend mode it should
> blink - that won't change either
> - pressing the power button obviously doesn't wake the system up; need
> to hard reboot
> 
> 3. Now, when booting again, after an unsuccessful suspend and hard
> reboot, something happens to my network card (and it doesn't matter
> what is the next kernel I boot from - it can be any 'good' or 'bad'
> one):
> - in Gnome, the gnome-panel network indicator shows my connection as
> disabled (wired eth0 - the only one I use); enabling it doesn't bring
> my network up
> 
> 4. After re-booting from any of the 'good' or 'bad' kernels my network
> connection is working again.
> -----------------------
> 
> Bisecting turned up the following commit. Reverting it in 2.6.36-rc1
> results in a system that works.
> 
> commit bd25f4dd6972755579d0ea50d1a5ace2e9b00d1a
> Author: Arnd Bergmann <arnd@...db.de>
> Date:   Sun Jul 11 15:34:05 2010 +0200
> 
>     HID: hiddev: use usb_find_interface, get rid of BKL
> 
>     This removes the private hiddev_table in the usbhid
>     driver and changes it to use usb_find_interface
>     instead.
> 
>     The advantage is that we can avoid the race between
>     usb_register_dev and usb_open and no longer need the
>     big kernel lock.
> 
>     This doesn't introduce race condition -- the intf pointer could be
>     invalidated only in hiddev_disconnect() through usb_deregister_dev(),
>     but that will block on minor_rwsem and not actually remove the device
>     until usb_open().
> -----------------------
> 
> Despite mentioned issues with network (occurring every time after
> unsuccessful suspend > hard restart) the bisecting turned up a commit
> which isn't rather related to network. But I can confirm that
> reverting only this one commit in 2.6.36-rc1
> [da5cabf80e2433131bf0ed8993abc0f7ea618c73] fixes the whole problem -
> suspend works OK and I have no issues with my network after waking the
> system up, neither after re-booting from the same or any other kernel.
> 
> Please let me know what further details should I provide. Any logs,
> hardware specifications? I've also made a brief log recording the
> bisect if anyone would need it.

Well, we should let the HID maintainer know about the problem (CC added).

Thanks,
Rafael
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