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Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1pEv0g-002mMs-0C; Mon, 09 Jan 2023 16:28:30 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id DEE513001E5; Mon, 9 Jan 2023 17:28:32 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 8A07E20086EAB; Mon, 9 Jan 2023 17:28:32 +0100 (CET) Date: Mon, 9 Jan 2023 17:28:32 +0100 From: Peter Zijlstra To: Linus Torvalds Cc: Heiko Carstens , corbet@lwn.net, will@kernel.org, boqun.feng@gmail.com, mark.rutland@arm.com, catalin.marinas@arm.com, dennis@kernel.org, tj@kernel.org, cl@linux.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, Herbert Xu , davem@davemloft.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, joro@8bytes.org, suravee.suthikulpanit@amd.com, robin.murphy@arm.com, dwmw2@infradead.org, baolu.lu@linux.intel.com, Arnd Bergmann , penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, Andrew Morton , vbabka@suse.cz, roman.gushchin@linux.dev, 42.hyeyoo@gmail.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org, linux-crypto@vger.kernel.org, iommu@lists.linux.dev, linux-arch@vger.kernel.org Subject: Re: [RFC][PATCH 11/12] slub: Replace cmpxchg_double() Message-ID: References: <20221219153525.632521981@infradead.org> <20221219154119.550996611@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 0037F180009 X-Stat-Signature: 8gj78b8witgimb5mm58kg1ftcu98hb69 X-HE-Tag: 1673281745-149077 X-HE-Meta: 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 6jYNNpRI deaGa X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jan 03, 2023 at 11:08:29AM -0800, Linus Torvalds wrote: > But I *do* note that this patch seems to be the only one that depends > on the new this_cpu_cmpxchg() updates to make it just automatically do > the right thing for a 128-bit value. And I have to admit that all > those games with __pcpu_cast_128() make no sense to me. Why isn't it > just using "u128" everywhere without any odd _Generic() games? I ran into a ton of casting trouble when compiling kernel/fork.c which uses this_cpu_cmpxchg() on a pointer type and the compiler hates casting pointers to an integer that is not the exact same size.