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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: Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org 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!).