linux-kernel - Re: [PATCH v3] devres: Explicitly align datai[] to 64-bit

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Message-ID: <20180709140717.GR2476@hirez.programming.kicks-ass.net>
Date:   Mon, 9 Jul 2018 16:07:17 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Alexey Brodkin <Alexey.Brodkin@...opsys.com>
Cc:     linux-kernel@...r.kernel.org, linux-snps-arc@...ts.infradead.org,
        linux-arch@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        David Laight <David.Laight@...LAB.COM>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will.deacon@....com>, Greg KH <greg@...ah.com>,
        stable@...r.kernel.org
Subject: Re: [PATCH v3] devres: Explicitly align datai[] to 64-bit

On Mon, Jul 09, 2018 at 04:45:50PM +0300, Alexey Brodkin wrote:
> --- a/drivers/base/devres.c
> +++ b/drivers/base/devres.c
> @@ -24,8 +24,12 @@ struct devres_node {
>  
>  struct devres {
>  	struct devres_node		node;
> -	/* -- 3 pointers */
> -	unsigned long long		data[];	/* guarantee ull alignment */
> +	/*
> +	 * data[] must be 64 bit aligned even on 32 bit architectures
> +	 * because it might be accessed by instructions that require
> +	 * aligned memory arguments such as atomic64_t.
> +	 */
> +	u8 __aligned(8)			data[];
>  };

Seeing that this ends up in a semi generic allocation thing, I don't
feel this should be different from ARCH_KMALLOC_MINALIGN.