linux-kernel - Re: [PATCH] compiler-gcc*.h: remove inaccurate comment about 'asm goto' miscompiles

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Date:	Thu, 06 Nov 2014 15:44:27 +0100
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Steven Noonan <steven@...inklabs.net>, linux-kernel@...r.kernel.org
CC:	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH] compiler-gcc*.h: remove inaccurate comment about 'asm
 goto' miscompiles

On 10/26/2014 12:09 AM, Steven Noonan wrote:
> The bug referenced by the comment in this commit was not completely fixed in
> GCC 4.8.2, as I mentioned in a thread back in February[1]. The conclusion at
> that time was to make the quirk unconditional until the bug could be found and
> fixed in GCC. Unfortunately, when I submitted the patch (commit a9f18034)
> I left a comment in that claimed the bug was fixed in GCC 4.8.2+.  This comment
> is inaccurate, and should be removed.

I believe the original gcc bug was indeed fixed, but there's another bug [1] not
yet fixed, see also [2]. So maybe the new bug number should be added to the
comments?

Vlastimil

[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61772
[2] https://lkml.org/lkml/2014/7/10/398

> [1] https://lkml.org/lkml/2014/2/12/797
> Signed-off-by: Steven Noonan <steven@...inklabs.net>
> Cc: Ingo Molnar <mingo@...nel.org>
> ---
>  include/linux/compiler-gcc4.h | 1 -
>  include/linux/compiler-gcc5.h | 1 -
>  2 files changed, 2 deletions(-)
> 
> diff --git a/include/linux/compiler-gcc4.h b/include/linux/compiler-gcc4.h
> index 2507fd2..d1a5582 100644
> --- a/include/linux/compiler-gcc4.h
> +++ b/include/linux/compiler-gcc4.h
> @@ -71,7 +71,6 @@
>   *   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
>   *
>   * Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
> - * Fixed in GCC 4.8.2 and later versions.
>   *
>   * (asm goto is automatically volatile - the naming reflects this.)
>   */
> diff --git a/include/linux/compiler-gcc5.h b/include/linux/compiler-gcc5.h
> index cdd1cc2..c8c5659 100644
> --- a/include/linux/compiler-gcc5.h
> +++ b/include/linux/compiler-gcc5.h
> @@ -53,7 +53,6 @@
>   *   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
>   *
>   * Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
> - * Fixed in GCC 4.8.2 and later versions.
>   *
>   * (asm goto is automatically volatile - the naming reflects this.)
>   */
> 

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