linux-kernel - Re: [Bug #13337] [post 2.6.29 regression] hang during suspend of b44/b43 modules

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Message-ID: <87my6ovpjv.fsf@scholz.fias.uni-frankfurt.de>
Date:	Tue, 28 Jul 2009 16:40:36 +0200
From:	Jan Scholz <scholz@...s.uni-frankfurt.de>
To:	Johannes Berg <johannes@...solutions.net>
Cc:	Jan Scholz <scholz@...s.uni-frankfurt.de>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	Tomas Janousek <tomi@...i.cz>,
	"John W. Linville" <linville@...driver.com>
Subject: Re: [Bug #13337] [post 2.6.29 regression] hang during suspend of b44/b43 modules

Johannes Berg <johannes@...solutions.net> writes:

> On Sat, 2009-07-11 at 19:20 +0200, Jan Scholz wrote:
>> Johannes Berg <johannes@...solutions.net> writes:
>> 
>> > On Sat, 2009-07-11 at 16:07 +0200, Jan Scholz wrote:
>> >
>> >> > Jan, can you run with console_suspend=0 (or whatever it is now, Rafael
>> >> > will correct me if I'm wrong) that should work on your platform, and put
>> >> > a bunch of printk calls into __ieee80211_suspend in net/mac80211/pm.c to
>> >> > see where in there it's hanging?
>> >> 
>> >> Did that, seems like it hangs in
>> >>   drv_remove_interface(local, &conf);
>> >
>> > Ok, thanks! I was going to suggest doing the same in
>> > b43_op_remove_interface in drivers/net/wireless/b43/main.c, but I think
>> > the problem is just that we have an ordering problem and call drv_stop
>> > before drv_remove_interface. I'll try to come up with a fix soon --
>> > might not be able to today though, in the meantime I guess you can just
>> > move the drv_stop call to the end of the function and tell me if that
>> > works -- that would be racy but should be ok most of the time.
>> 
>> I moved drv_stop to the end of the function (see patch below) and now
>> suspend works fine.
>
> Thanks, that's what I suspected -- I'll take a closer look into what is
> required to make it race-free against RX.
>

Hi,

The bug is still present in v2.6.31-rc4, it's still fixed by the patch
(see below) suggested as a test by Johannes.

Regards,
   Jan

>> diff --git a/net/mac80211/pm.c b/net/mac80211/pm.c
>> index 7a549f9..0ac15fb 100644
>> --- a/net/mac80211/pm.c
>> +++ b/net/mac80211/pm.c
>> @@ -58,12 +58,6 @@ int __ieee80211_suspend(struct ieee80211_hw *hw)
>>  	/* flush again, in case driver queued work */
>>  	flush_workqueue(local->hw.workqueue);
>>  
>> -	/* stop hardware - this must stop RX */
>> -	if (local->open_count) {
>> -		ieee80211_led_radio(local, false);
>> -		drv_stop(local);
>> -	}
>> -
>>  	/* remove STAs */
>>  	spin_lock_irqsave(&local->sta_lock, flags);
>>  	list_for_each_entry(sta, &local->sta_list, list) {
>> @@ -111,6 +105,12 @@ int __ieee80211_suspend(struct ieee80211_hw *hw)
>>  		drv_remove_interface(local, &conf);
>>  	}
>>  
>> +	/* stop hardware - this must stop RX */
>> +	if (local->open_count) {
>> +		ieee80211_led_radio(local, false);
>> +		drv_stop(local);
>> +	}
>> +
>>  	local->suspended = true;
>>  	local->quiescing = false;
>> 

-- 
 Jan Scholz                                ____  ____    __    ___ 
                                          ( ___)(_  _)  /__\  / __)
 Frankfurt Institute for Advanced Studies  )__)  _)(_  /(__)\ \__ \
                                          (__)  (____)(__)(__)(___/
 Goethe Universitaet Frankfurt
 Ruth-Moufang-Str. 1                             Tel. 069-798-47534
 60438 Frankfurt am Main
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