linux-kernel - Re: [PATCH 1/2] IB/hfi1: Fix a parameter of find_first

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Date:   Fri, 2 Sep 2016 13:11:53 -0400
From:   Doug Ledford <dledford@...hat.com>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        mike.marciniszyn@...el.com, dennis.dalessandro@...el.com,
        sean.hefty@...el.com, hal.rosenstock@...il.com
Cc:     linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kernel Janitors <kernel-janitors@...r.kernel.org>
Subject: Re: [PATCH 1/2] IB/hfi1: Fix a parameter of find_first_bit.

On 8/27/2016 1:25 AM, Christophe JAILLET wrote:
> Le 26/08/2016 à 15:35, Doug Ledford a écrit :
>> On 8/26/2016 12:49 AM, Christophe JAILLET wrote:
>>> The 2nd parameter of 'find_first_bit' is the number of bits to search.
>>> In this case, we are passing 'sizeof(unsigned long)' which is likely to
>>> be 4 or 8.
>> If the size can be 4 or 8, then using 64 universally is not correct.
>> Why not use sizeof() * 8 (or << 3)?
> I agree with you...
> 
> BTW, the log message is wrong. 'port_mask' is a u64. (not an unsigned
> long). So the sizeof should always be 8.
> (cut and paste error from another patch, sorry)

Log message modified, then patch modified to use sizeof() * 8, result
applied.  Thanks.

>>
>>> It is likely that the number of bits of 'port_mask' was expected
>>> here. This
>>> variable is a 'u64', so use 64 instead.
>>>
>>> It has been spotted by the following coccinelle script:
>>> @@
>>> expression ret, x;
>>>
>>> @@
>>> *  ret = \(find_first_bit \| find_first_zero_bit\) (x, sizeof(...));
>>>
>>> Signed-off-by: Christophe JAILLET
>>> <christophe.jaillet-39ZsbGIQGT5GWvitb5QawA@...lic.gmane.org>
>>> ---
>>> Not sure that using 64 directly is the best option.
>>> Maybe '8 * sizeof(port_mask)' as used in the same file for
>>> 'for_each_set_bit' would be better
>>> ---
> ... as noted here
> 
> Would you like a v2 patch or, will you update it by yourself?
> 
> Best regards,
> CJ
> 
> ---
> L'absence de virus dans ce courrier électronique a été vérifiée par le
> logiciel antivirus Avast.
> https://www.avast.com/antivirus
> 


-- 
Doug Ledford <dledford@...hat.com>
    GPG Key ID: 0E572FDD



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