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Mon, 15 Sep 2025 07:20:47 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ThreadId: A-ya5D5_Z2ZZ Date: Mon, 15 Sep 2025 13:20:18 +0200 From: "Arnd Bergmann" To: "Finn Thain" , "Peter Zijlstra" Cc: "Will Deacon" , "Andrew Morton" , "Boqun Feng" , "Jonathan Corbet" , "Mark Rutland" , linux-kernel@vger.kernel.org, Linux-Arch , "Geert Uytterhoeven" , linux-m68k@vger.kernel.org Message-Id: <57bca164-4e63-496d-9074-79fd89feb835@app.fastmail.com> In-Reply-To: <8247e3bd-13c2-e28c-87d8-5fd1bfed7104@linux-m68k.org> References: <20250915080054.GS3419281@noisy.programming.kicks-ass.net> <4b687706-a8f1-5f51-6e64-6eb09ae3eb5b@linux-m68k.org> <20250915100604.GZ3245006@noisy.programming.kicks-ass.net> <8247e3bd-13c2-e28c-87d8-5fd1bfed7104@linux-m68k.org> Subject: Re: [RFC v2 3/3] atomic: Add alignment check to instrumented atomic operations Content-Type: text/plain Content-Transfer-Encoding: 7bit On Mon, Sep 15, 2025, at 12:37, Finn Thain wrote: > On Mon, 15 Sep 2025, Peter Zijlstra wrote: >> >> > When you do atomic operations on atomic_t or atomic64_t, (sizeof(long) >> > - 1) probably doesn't make much sense. But atomic operations get used on >> > scalar types (aside from atomic_t and atomic64_t) that don't have natural >> > alignment. Please refer to the other thread about this: >> > https://lore.kernel.org/all/ed1e0896-fd85-5101-e136-e4a5a37ca5ff@linux-m68k.org/ >> >> Perhaps set ARCH_SLAB_MINALIGN ? >> > > That's not going to help much. The 850 byte offset of task_works into > struct task_struct and the 418 byte offset of exit_state in struct > task_struct are already misaligned. Has there been any progress on building m68k kernels with -mint-align? IIRC there are only a small number of uapi structures that need __packed annotations to maintain the existing syscall ABI. Arnd