From mboxrd@z Thu Jan  1 00:00:00 1970
From: gang.chen@asianux.com (Chen Gang)
Date: Sat, 05 Oct 2013 08:11:55 +0800
Subject: [PATCH 2/2] ARM: include: asm: use 'int' instead of 'unsigned
 long' for normal register variables within atomic.h
In-Reply-To: <524F5566.4010204@asianux.com>
References: <20130930161149.GI26036@mudshark.cambridge.arm.com>
 <524A2DE7.8040208@asianux.com>
 <20131001090119.GA17629@mudshark.cambridge.arm.com>
 <524ABA20.6060106@asianux.com>
 <20131002104158.GD28311@mudshark.cambridge.arm.com>
 <524C3981.20307@asianux.com> <524D416B.5090709@asianux.com>
 <20131003163200.GE7408@mudshark.cambridge.arm.com>
 <524E8FBC.2080200@asianux.com>
 <20131004153742.GR24303@mudshark.cambridge.arm.com>
 <20131004154208.GS24303@mudshark.cambridge.arm.com>
 <524F5566.4010204@asianux.com>
Message-ID: <524F594B.1070106@asianux.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 10/05/2013 07:55 AM, Chen Gang wrote:
> On 10/04/2013 11:42 PM, Will Deacon wrote:
>> On Fri, Oct 04, 2013 at 04:37:42PM +0100, Will Deacon wrote:
>>> On Fri, Oct 04, 2013 at 10:51:56AM +0100, Chen Gang wrote:
>>>> On 10/04/2013 12:32 AM, Will Deacon wrote:
>>>>> The problem with arm64 is that we're using *unsigned long* for 32-bit
>>>>> clear_mask, which is definitely wrong because it's 64-bit (another patch to
>>>>> fix this!).
>>>>>
>>>>
>>>> At least, that is not a bug.
>>>
>>> Sure it is. What if the adjacent 32-bit value was being accessed by another
>>> CPU under a spinlock?
>>
>> (Oh, ok, that would still work on arm because of the way the exclusive
>> monitor is implemented, but we shouldn't rely on that).
>>
> 
> Hmm... in my opinion, we need divide atomic_*_mask() into 32-bit and
> 64-bit versions. We already have demands to only use 32-bit value to
> express mask (can save size), and may have demands to use 64-bit too.
> 
> If so, can easily standard all atomic_*_mask() which are in asm-generic
> and various architectures: use atomic_*_mask() for 32-bit mask, and use
> atomic64_*_mask() for 64-bit mask (can delayed before get real demands).
> 
> Since it is about API, so it is related with asm-generic and all other
> architectures interfaces, it is better to consider about them firstly
> before the fix under arm64.
> 
> 
> And also, excuse me, I am not quite familiar with "exclusive monitor",
> could you please provide more details about it?
> 

If in arm64 with allmodconfig, we only need atomic_*_mask() for 32-bit
mask, don't need 64-bit, we can use 'unsigned int' instead of 'unsigned
long' (need not consider about asm-generic and other architectures).



> 
>> Will
>>
>>
> 
> 
> Thanks.
> 


-- 
Chen Gang