linux-kernel - Re: [PATCH v2] devres: Really align data field to unsigned long long

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Date:   Sun, 8 Jul 2018 20:40:49 +0200
From:   Greg KH <greg@...ah.com>
To:     Alexey Brodkin <alexey.brodkin@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-snps-arc@...ts.infradead.org,
        linux-arch@...r.kernel.org, Alexey Brodkin <abrodkin@...opsys.com>,
        Thomas Gleixner <tglx@...utronix.de>, stable@...r.kernel.org
Subject: Re: [PATCH v2] devres: Really align data field to unsigned long long

On Sun, Jul 08, 2018 at 08:56:21PM +0300, Alexey Brodkin wrote:
> Depending on ABI "long long" type of a particular 32-bit CPU
> might be aligned by either word (32-bits) or double word (64-bits).
> Make sure "data" is really 64-bit aligned for any 32-bit CPU.
> 
> At least for 32-bit ARC cores ABI requires "long long" types
> to be aligned by normal 32-bit word. This makes "data" field aligned to
> 12 bytes. Which is still OK as long as we use 32-bit data only.
> 
> But once we want to use native atomic64_t type (i.e. when we use special
> instructions LLOCKD/SCONDD for accessing 64-bit data) we easily hit
> misaligned access exception.
> 
> That's because even on CPUs capable of non-aligned data access LL/SC
> instructions require strict alignment.
> 
> Signed-off-by: Alexey Brodkin <abrodkin@...opsys.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: stable@...r.kernel.org
> ---
> 
> Changes v1 -> v2:
> 
>  * Reworded commit message
>  * Inserted comment right in source [Thomas]
> 
>  drivers/base/devres.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)

Always use scripts/get_maintainer.pl to properly cc: the needed
developer/maintainer.  As it is, this patch is going to get dropped on
the floor, sorry...

greg k-h