Message-id: <53503E9F.9050800@samsung.com>
Date: Thu, 17 Apr 2014 14:50:39 -0600
From: Shuah Khan <shuah.kh@samsung.com>
Reply-to: shuah.kh@samsung.com
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To: Tejun Heo <tj@kernel.org>
Cc: gregkh@linuxfoundation.org, m.chehab@samsung.com,
        rafael.j.wysocki@intel.com, linux@roeck-us.net, toshi.kani@hp.com,
        linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
        shuahkhan@gmail.com
Subject: Re: [RFC PATCH 2/2] drivers/base: add managed token devres interfaces
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On 04/17/2014 02:10 PM, Tejun Heo wrote:
> On Thu, Apr 17, 2014 at 02:01:32PM -0600, Shuah Khan wrote:
>> Operating on the lock should be atomic, which is what devres_update()
>> is doing. It can be simplified as follows by holding devres_lock
>> in devm_token_lock().
>>
>> spin_lock_irqsave(&dev->devres_lock, flags);
>> if (tkn_ptr->status == TOKEN_DEVRES_FREE)
>> 	tkn_ptr->status = TOKEN_DEVRES_BUSY;
>> spin_unlock_irqrestore(&dev->devres_lock, flags);
>>
>> Is this in-line with what you have in mind?
>
> How is that different from tkn_ptr->status = TOKEN_DEVRES_BUSY?
>

I see what you are saying. The code path doesn't ensure two threads
not getting the lock. I have a bug in here that my rc settings aren't
protected. You probably noticed that the RFC tag on the patch and this
isn't fully cooked yet.

I started working on driver changes that use this token and I might have
to add owner for the token as well. I hope to work these details out and
send a real patch.

thanks,
-- Shuah

-- 
Shuah Khan
Senior Linux Kernel Developer - Open Source Group
Samsung Research America(Silicon Valley)
shuah.kh@samsung.com | (970) 672-0658
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