linux-kernel - Re: [patch -stable] firware_class oops: fix firmware_loading

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Message-ID: <4ABB8CB5.9080402@in.ibm.com>
Date:	Thu, 24 Sep 2009 20:43:57 +0530
From:	Sachin Sant <sachinp@...ibm.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Frederik Deweerdt <frederik.deweerdt@...og.eu>, greg@...ah.org,
	Lars Ericsson <Lars_Ericsson@...ia.com>,
	David.Woodhouse@...el.com, linux-kernel@...r.kernel.org,
	"'Ivo van Doorn'" <ivdoorn@...il.com>
Subject: Re: [patch -stable] firware_class oops: fix firmware_loading_store
 locking

Linus Torvalds wrote:
> I don't think this is correct.
>
> I think you should protect the FW_STATUS_LOADING bit too, shouldn't you?
>
> As it is, it does this:
>
> 	if (test_bit(FW_STATUS_LOADING, &fw_priv->status)) {
> 		mutex_lock(&fw_lock);
> 		...
> 		clear_bit(FW_STATUS_LOADING, &fw_priv->status);
> 		mutex_unlock(&fw_lock);
> 		break;
> 	}
>
> and if this code can race (which it obviously can, since your addition of 
> fw_lock mutex matters), then I think it can race on that FW_STATUS_LOADING 
> bit too. No?
>
> So my gut feel is that the whole damn function should be protected by the 
> mutex_lock thing. IOW, the patch would be something like the appended.
>
> UNTESTED. Somebody needs to test this, verify, and send it back to me.
>   
I did a quick boot test with this patch and didn't find any issues.

But that said i haven't been able to recreate the problem reported by Lars,
so not sure how relevant would be the test results from me.

Thanks
-Sachin


-- 

---------------------------------
Sachin Sant
IBM Linux Technology Center
India Systems and Technology Labs
Bangalore, India
---------------------------------

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