linux-kernel - Re: [PATCH] workqueue: fix enum type for gcc-13

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Date:   Tue, 9 May 2023 11:26:14 +0800
From:   Lai Jiangshan <jiangshanlai@...il.com>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Tejun Heo <tj@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Richard Clark <richard.xnu.clark@...il.com>,
        Jonathan Neuschäfer <j.neuschaefer@....net>,
        Andrey Grodzovsky <andrey.grodzovsky@....com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] workqueue: fix enum type for gcc-13

On Wed, Jan 18, 2023 at 12:40 AM Arnd Bergmann <arnd@...nel.org> wrote:
>
> From: Arnd Bergmann <arnd@...db.de>
>
> In gcc-13, the WORK_STRUCT_WQ_DATA_MASK constant is a signed 64-bit
> type on 32-bit architectures because the enum definition has both
> negative numbers and numbers above LONG_MAX in it:
>
> kernel/workqueue.c: In function 'get_work_pwq':
> kernel/workqueue.c:709:24: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
>   709 |                 return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
>       |                        ^
> kernel/workqueue.c: In function 'get_work_pool':
> kernel/workqueue.c:737:25: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
>   737 |                 return ((struct pool_workqueue *)
>       |                         ^
> kernel/workqueue.c: In function 'get_work_pool_id':
> kernel/workqueue.c:759:25: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
>   759 |                 return ((struct pool_workqueue *)
>       |                         ^
>
> Change the enum definition to ensure all values can fit into
> the range of 'unsigned long' on all architectures.
>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  include/linux/workqueue.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
> index ac551b8ee7d9..fba8d0154a1e 100644
> --- a/include/linux/workqueue.h
> +++ b/include/linux/workqueue.h
> @@ -83,7 +83,7 @@ enum {
>
>         /* convenience constants */
>         WORK_STRUCT_FLAG_MASK   = (1UL << WORK_STRUCT_FLAG_BITS) - 1,
> -       WORK_STRUCT_WQ_DATA_MASK = ~WORK_STRUCT_FLAG_MASK,
> +       WORK_STRUCT_WQ_DATA_MASK = (unsigned long)~WORK_STRUCT_FLAG_MASK,
>         WORK_STRUCT_NO_POOL     = (unsigned long)WORK_OFFQ_POOL_NONE << WORK_OFFQ_POOL_SHIFT,

Tested with "old" gcc: 7.3.1

Tested-by: Lai Jiangshan<jiangshanlai@...il.com>

But I personally prefer to redefine them as non-enum.

>
>         /* bit mask for work_busy() return values */
> --
> 2.39.0
>