linux-kernel - Re: [PATCH 1/1] hung_task: fix warnings by enforcing alignment on lock structures

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Message-ID: <29f4f58e-2f14-99c8-3899-3b0be79382c2@linux-m68k.org>
Date: Sun, 24 Aug 2025 10:47:43 +1000 (AEST)
From: Finn Thain <fthain@...ux-m68k.org>
To: Lance Yang <lance.yang@...ux.dev>
cc: kernel test robot <lkp@...el.com>, akpm@...ux-foundation.org, 
    geert@...ux-m68k.org, mhiramat@...nel.org, senozhatsky@...omium.org, 
    oe-kbuild-all@...ts.linux.dev, amaindex@...look.com, 
    anna.schumaker@...cle.com, boqun.feng@...il.com, ioworker0@...il.com, 
    joel.granados@...nel.org, jstultz@...gle.com, kent.overstreet@...ux.dev, 
    leonylgao@...cent.com, linux-kernel@...r.kernel.org, 
    linux-m68k@...ts.linux-m68k.org, longman@...hat.com, mingo@...hat.com, 
    mingzhe.yang@...com, oak@...sinkinet.fi, rostedt@...dmis.org, 
    tfiga@...omium.org, will@...nel.org, stable@...r.kernel.org
Subject: Re: [PATCH 1/1] hung_task: fix warnings by enforcing alignment on
 lock structures


On Sun, 24 Aug 2025, kernel test robot wrote:

> 
> All warnings (new ones prefixed by >>):
> 
>    In file included from sound/soc/codecs/mt6660.c:15:
> >> sound/soc/codecs/mt6660.h:28:1: warning: alignment 1 of 'struct mt6660_chip' is less than 8 [-Wpacked-not-aligned]
>       28 | };
>          | ^
> >> sound/soc/codecs/mt6660.h:25:22: warning: 'io_lock' offset 49 in 'struct mt6660_chip' isn't aligned to 8 [-Wpacked-not-aligned]
>       25 |         struct mutex io_lock;
>          |                      ^~~~~~~
> 

Misalignment warnings like this one won't work if you just pick an 
alignment arbitrarily i.e. to suit whatever bitfield you happen to need.

Instead, I think I would naturally align the actual locks, that is, 
arch_spinlock_t and arch_rwlock_t in include/linux/spinlock_types*.h.