linux-kernel - Re: [PATCH] workqueue: Fix an object aliasing bug with `work_data

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Message-ID: <20160525204050.GK3354@mtj.duckdns.org>
Date:	Wed, 25 May 2016 16:40:50 -0400
From:	Tejun Heo <tj@...nel.org>
To:	"Maciej W. Rozycki" <macro@...tec.com>
Cc:	Lai Jiangshan <jiangshanlai@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] workqueue: Fix an object aliasing bug with
 `work_data_bits'

On Tue, May 17, 2016 at 12:04:33PM +0100, Maciej W. Rozycki wrote:
> Fix an aliasing issue causing a MIPS port build error:
> 
> In file included from include/linux/srcu.h:34:0,
>                  from include/linux/notifier.h:15,
>                  from ./arch/mips/include/asm/uprobes.h:9,
>                  from include/linux/uprobes.h:61,
>                  from include/linux/mm_types.h:13,
>                  from ./arch/mips/include/asm/vdso.h:14,
>                  from arch/mips/vdso/vdso.h:27,
>                  from arch/mips/vdso/gettimeofday.c:11:
> include/linux/workqueue.h: In function 'work_static':
> include/linux/workqueue.h:186:2: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
>   return *work_data_bits(work) & WORK_STRUCT_STATIC;
>   ^

Umm... the kernel is built explicitly with -fno-strict-aliasing and
it's not something individual archs can opt out.

Thanks.

-- 
tejun