linux-kernel - Re: [PATCH] cris: arch-v10: kernel: kgdb: let is_dyn

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Message-ID: <COL130-W89DC3ADE946F9BD990C844B9900@phx.gbl>
Date:	Thu, 9 Jul 2015 09:26:57 +0800
From:	gchen gchen <xili_gchen_5257@...mail.com>
To:	"Valdis.Kletnieks@...edu" <valdis.kletnieks@...edu>
CC:	"starvik@...s.com" <starvik@...s.com>,
	"jesper.nilsson@...s.com" <jesper.nilsson@...s.com>,
	"linux-cris-kernel@...s.com" <linux-cris-kernel@...s.com>,
	kernel mailing list <linux-kernel@...r.kernel.org>,
	Hans-Peter Nilsson <hans-peter.nilsson@...s.com>
Subject: Re: [PATCH] cris: arch-v10: kernel: kgdb: let is_dyn_brkp as extern
 variable

On 07/07/2015 06:28 AM, Chen Gang wrote:
> On 7/6/15 18:31, Valdis.Kletnieks@...edu wrote:
>> On Mon, 06 Jul 2015 15:49:20 +0800, Chen Gang said:
>>> On 07/06/2015 02:25 AM, Valdis.Kletnieks@...edu wrote:
>>>> On Sun, 05 Jul 2015 06:07:54 +0800, Chen Gang said:
>>>>> For upstream cris toolchain (gcc is 6.0
>>>>
>>>> typo?
>>>>
>>>
>>> Do you mean "toolchain" -> "tool chain"?
>>
>> No, I was wondering where a gcc 6.0 managed to escape when 5.1 just got
>> released about 2 weeks ago....
>>
>

Oh, sorry, gcc 5.1 is the same, and at present, for me:

 - The new gcc have additional optimization for the static variables. It
   should notice about the related c code when optimizing, but gcc has
   no idea about assembly code (it should passes them to gas, directly).

 - If one want gcc skip the related optimization, it can use 'volatile'
   for it (the static variable which may be used by both c code and
   assembly code in one file).

 - So I guess, we need add 'volatile' to the related static variable, we
   do not want to disable this optimization only because of this issue.

Welcome any additional ideas, suggestions and completions.

> OK, thanks. At present, gcc 6.0 is the latest in master branch.
>
> After check fedora released toolchain (gcc 4.9.1, binutils 2.25), it has
> no issue (support static variable in our case). So this patch can be
> dropped, and I shall try:
>
>  - Use the same configuration parameters of fedora released toolchain to
>    build the upstream latest cross toolchain again, and try.
>
>  - If it still has issue (not support static variable), I shall try to
>    fix it.
>
>
> Thanks.
>

--
Chen Gang

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