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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 1pFBrQ-0035qA-1F; Tue, 10 Jan 2023 10:28:05 +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 D9BAF3001F7; Tue, 10 Jan 2023 11:28:07 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 75EEE2C539CAD; Tue, 10 Jan 2023 11:28:07 +0100 (CET) Date: Tue, 10 Jan 2023 11:28:07 +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-Queue-Id: AF7631C0003 X-Rspamd-Server: rspam01 X-Stat-Signature: 95m58gfcy48ss3nkju1id3apwhs1dic1 X-HE-Tag: 1673346521-770771 X-HE-Meta: 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 F7nf3uKg 8OPx9 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 Mon, Jan 09, 2023 at 04:02:33PM -0600, Linus Torvalds wrote: > On Mon, Jan 9, 2023 at 10:29 AM Peter Zijlstra wrote: > > > > 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. > > Ahh. Yeah - not because that code needs or wants the 128-bit case, but > because the macro expands to all sizes in a switch statement, so the > compiler sees all the cases even if only one is then statically > picked. > > So the silly casts are for all the cases that never matter. > > Annoying. Yes, very. This seems to compile (and boot). Let me go update the others and push it out for the robots to have a go. #define percpu_cmpxchg128_op(size, qual, _var, _oval, _nval) \ ({ \ union { \ typeof(_var) full; \ struct { \ u64 low, high; \ }; \ } old__, new__; \ \ old__.full = _oval; \ new__.full = _nval; \ \ asm qual ("cmpxchg16b " __percpu_arg([var]) \ : [var] "+m" (_var), \ "+a" (old__.low), \ "+d" (old__.high) \ : "b" (new__.low), \ "c" (new__.high) \ : "memory"); \ \ old__.full; \ })