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From:   David Laight <David.Laight@ACULAB.COM>
To:     'Arnd Bergmann' <arnd@kernel.org>, Tejun Heo <tj@kernel.org>
CC:     Arnd Bergmann <arnd@arndb.de>,
        Lai Jiangshan <jiangshanlai@gmail.com>,
        Richard Clark <richard.xnu.clark@gmail.com>,
        =?iso-8859-1?Q?Jonathan_Neusch=E4fer?= <j.neuschaefer@gmx.net>,
        "Andrey Grodzovsky" <andrey.grodzovsky@amd.com>,
        Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] workqueue: fix enum type for gcc-13
Thread-Topic: [PATCH] workqueue: fix enum type for gcc-13
Thread-Index: AQHZKpKFluEYnxF+H0aveYqsdFdjha6j5uGA
Date:   Wed, 18 Jan 2023 09:31:18 +0000
Message-ID: <99ea6e86d2594b40a6de96cc821c447b@AcuMS.aculab.com>
References: <20230117164041.1207412-1-arnd@kernel.org>
In-Reply-To: <20230117164041.1207412-1-arnd@kernel.org>
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From: Arnd Bergmann
> Sent: 17 January 2023 16:41
> 
> 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:
> 
...
>  	/* 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,

How can that make any difference?
You aren't changing the value or type (which makes no difference)
of WORK_STRUCT_WQ_DATA_MASK.
Indeed you require it to have the high bit set.

So if the enum contains a -1 somewhere gcc-13 will promote
everything to s64.

Either declare gcc-13 as 'BROKEN' or change the:
	return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
to
	return (void *)(data & ~WORK_STRUCT_FLAG_MASK);

or use #defines.

	David

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