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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 1p8LR1-00Dq0t-2q; Thu, 22 Dec 2022 13:16:32 +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)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id D4E3C30006D; Thu, 22 Dec 2022 14:16:28 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 5D8FC2CEAF0FB; Thu, 22 Dec 2022 14:16:28 +0100 (CET) Date: Thu, 22 Dec 2022 14:16:28 +0100 From: Peter Zijlstra To: Boqun Feng Cc: torvalds@linux-foundation.org, corbet@lwn.net, will@kernel.org, mark.rutland@arm.com, catalin.marinas@arm.com, dennis@kernel.org, tj@kernel.org, cl@linux.com, hca@linux.ibm.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 05/12] arch: Introduce arch_{,try_}_cmpxchg128{,_local}() Message-ID: References: <20221219153525.632521981@infradead.org> <20221219154119.154045458@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: rspam02 X-Rspamd-Queue-Id: C7A111C0009 X-Stat-Signature: xzyjynk59fs6cm64uuu9cckm9eiupdq7 X-HE-Tag: 1671715022-330353 X-HE-Meta: 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 p2IGTaEO nhoTw 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 Wed, Dec 21, 2022 at 05:25:20PM -0800, Boqun Feng wrote: > > +#define __CMPXCHG128(name, mb, cl...) \ > > +static __always_inline u128 \ > > +__lse__cmpxchg128##name(volatile u128 *ptr, u128 old, u128 new) \ > > +{ \ > > + union __u128_halves r, o = { .full = (old) }, \ > > + n = { .full = (new) }; \ > > + register unsigned long x0 asm ("x0") = o.low; \ > > + register unsigned long x1 asm ("x1") = o.high; \ > > + register unsigned long x2 asm ("x2") = n.low; \ > > + register unsigned long x3 asm ("x3") = n.high; \ > > + register unsigned long x4 asm ("x4") = (unsigned long)ptr; \ > > + \ > > + asm volatile( \ > > + __LSE_PREAMBLE \ > > + " casp" #mb "\t%[old1], %[old2], %[new1], %[new2], %[v]\n"\ > > + : [old1] "+&r" (x0), [old2] "+&r" (x1), \ > > + [v] "+Q" (*(unsigned long *)ptr) \ > > + : [new1] "r" (x2), [new2] "r" (x3), [ptr] "r" (x4), \ > > Issue #1: the line below can be removed, otherwise.. > > > + [oldval1] "r" (r.low), [oldval2] "r" (r.high) \ > > warning: > > ./arch/arm64/include/asm/atomic_lse.h: In function '__lse__cmpxchg128_mb': > ./arch/arm64/include/asm/atomic_lse.h:309:27: warning: 'r..low' is used uninitialized [-Wuninitialized] > 309 | [oldval1] "r" (r.low), [oldval2] "r" (r.high) > > > > + : cl); \ > > + \ > > + r.low = x0; r.high = x1; \ > > + \ > > + return r.full; \ > > +} > > + > > +__CMPXCHG128( , ) > > +__CMPXCHG128(_mb, al, "memory") > > + > > +#undef __CMPXCHG128 > > + > > #endif /* __ASM_ATOMIC_LSE_H */ > > --- a/arch/arm64/include/asm/cmpxchg.h > > +++ b/arch/arm64/include/asm/cmpxchg.h > > @@ -147,6 +147,19 @@ __CMPXCHG_DBL(_mb) > > > > #undef __CMPXCHG_DBL > > > > +#define __CMPXCHG128(name) \ > > +static inline long __cmpxchg128##name(volatile u128 *ptr, \ > > Issue #2: this should be > > static inline u128 __cmpxchg128##name(..) > > because cmpxchg* needs to return the old value. Duh.. fixed both. Pushed out to queue/core/wip-u128. I'll probably continue all this in two weeks (yay xmas break!).