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Tue, 28 May 2024 11:00:32 -0700 (PDT) Received: from andrea ([151.76.32.59]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a639ef1da1csm13068566b.147.2024.05.28.11.00.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 May 2024 11:00:31 -0700 (PDT) Date: Tue, 28 May 2024 20:00:26 +0200 From: Andrea Parri To: Alexandre Ghiti Cc: Jonathan Corbet , Paul Walmsley , Palmer Dabbelt , Albert Ou , Peter Zijlstra , Ingo Molnar , Will Deacon , Waiman Long , Boqun Feng , Arnd Bergmann , Leonardo Bras , Guo Ren , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, linux-arch@vger.kernel.org Subject: Re: [PATCH 4/7] riscv: Implement xchg8/16() using Zabha Message-ID: References: <20240528151052.313031-1-alexghiti@rivosinc.com> <20240528151052.313031-5-alexghiti@rivosinc.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240528151052.313031-5-alexghiti@rivosinc.com> > -#define __arch_xchg_masked(prepend, append, r, p, n) \ > +#define __arch_xchg_masked(swap_sfx, prepend, append, r, p, n) \ This actually indicates a problem in the current (aka, no Zabha) implementation: without your series, xchg16() gets mapped to lr.w a2,(a3) and a1,a2,a5 or a1,a1,a4 sc.w a1,a1,(a3) bnez a1,43c <.L0^B1> which is clearly wrong... (other "fully-ordered LR/SC sequences" instead follow the mapping lr.w a2,(a3) and a1,a2,a5 or a1,a1,a4 sc.w.rl a1,a1,(a3) bnez a1,43c <.L0^B1> fence rw,rw ) A similar consideration for xchg8(). Andrea