linux-kernel - Re: firmware_class warnings on resume

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Date:	Mon, 21 Dec 2015 14:46:15 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Laura Abbott <labbott@...hat.com>
Cc:	Ming Lei <ming.lei@...onical.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: firmware_class warnings on resume

On Mon, Dec 21, 2015 at 9:54 AM, Laura Abbott <labbott@...hat.com> wrote:
> On 12/20/2015 04:20 AM, Andy Lutomirski wrote:
>>
>> I hit this warning fairly frequently when resuming 4.4-rc5:
>>
>>          ret = usermodehelper_read_trylock();
>>          if (WARN_ON(ret)) {
>>              dev_err(device, "firmware: %s will not be loaded\n",
>>                  name);
>>              goto out;
>>          }
>>
>> It seems like it could be improved in two ways fairly easily:
>>
>> 1. Shouldn't firmware_class try the direct load before trying to get
>> the usermodehelper lock?
>>
>> 2. Why is the !NOWAIT case doing a trylock?  That seems wrong.
>>
>> --Andy
>>
>
>  I saw the same warning coming from the bluetooth stack, see the thread
> http://article.gmane.org/gmane.linux.kernel/1950940 and
> http://article.gmane.org/gmane.linux.kernel/1940130.
> At least in the bluetooth case, the conclusion was the firmware request
> should not be happening at that point in time and the reset_resume function
> should be implemented instead. I put that work aside and haven't picked
> it up again.

That's exactly the issue I'm seeing, and I think you're right.

Still, I think the firmware_class code is wrong, too.  If it wants to
warn, it should warn that firmware was requested too early in resume.
Using trylock as an excuse to fail a firmware load seems completely
bogus to me.

>
> Thanks,
> Laura



-- 
Andy Lutomirski
AMA Capital Management, LLC
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