linux-kernel - Re: [PATCH v2] cris: arch-v10: kgdb: Add volatile for static variable is_dyn

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Message-ID: <BLU436-SMTP410048B421910920AB4469B9750@phx.gbl>
Date:	Wed, 5 Aug 2015 22:19:35 +0800
From:	Chen Gang <xili_gchen_5257@...mail.com>
To:	Hans-Peter Nilsson <hans-peter.nilsson@...s.com>
CC:	starvik@...s.com, jespern@...s.com, linux-cris-kernel@...s.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] cris: arch-v10: kgdb: Add volatile for static variable
 is_dyn_brkp

On 8/4/15 23:01, Hans-Peter Nilsson wrote:
>> From: Chen Gang <xili_gchen_5257@...mail.com>
>> Date: Fri, 10 Jul 2015 23:50:07 +0200
> 
>> Within one C file, current gcc can optimize the global static variables
>> according to the C code, but it will skip assembly code -- it will pass
>> them to gas directly.
>>
>> if the static variable is used between C code and assembly code in one C
>> file (e.g. is_dyn_brkp in kgdb.c), it needs volatile to let gcc know it
>> should not be optimized, or it may cause issue.
> 
> In this case it's *mostly* a matter of taste but please avoid
> using volatile as a hammer when there are other tools available.
> 
>> -static unsigned char is_dyn_brkp = 0;
>> +static volatile unsigned char is_dyn_brkp;
> 
> Please instead use "__used", i.e.
> +static unsigned char __used is_dyn_brkp = 0;
> 

OK, thanks. I shall send patch v3 for it, next.

Thanks.
-- 
Chen Gang

Open, share, and attitude like air, water, and life which God blessed
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