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Tue, 03 Nov 2026 09:44:21 +0000 X-Mizu-Trace-ID: 4fced7d92f6bec66 X-Migadu-Flow: FLOW_OUT Date: Tue, 3 Nov 2026 17:44:13 +0800 From: Hao Li To: Tiezhu Yang Cc: Vlastimil Babka , Harry Yoo , Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , linux-mm@kvack.org, loongarch@lists.linux.dev, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1] mm/slub: Genericize x86-specific cmpxchg16b comment Message-ID: References: <20261102082730.12430-1-yangtiezhu@loongson.cn> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261102082730.12430-1-yangtiezhu@loongson.cn> X-Stat-Signature: 4r1o5rfhpksdchzr3xmf5uygeqmu5fz7 X-Rspamd-Queue-Id: 46D6240007 X-Rspam-User: X-Rspamd-Server: rspam11 X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-HE-Tag: 1793699063-961761 X-HE-Meta: U2FsdGVkX18vheNI2hYwFD8AqSkbH2zAL1oQdtr35lGTXhJX9T62i43itsjXHkkMogiF2x5jjtEM46JydFSmESrRHKSJwA6xNu1C6AbmivQXOxmphWIRwmqw7TZzdK7uIjHGj9b0en6UHr3DNcxaVm61hI+CO4ZNGVhwOrTvtrpXmxhk4oCdW3tGNwEAFyHkmkHVyE9MzQRwNCr51jgLBTZRMqHigYiaY883HoigduzzUXAF3uOQiw+HabSiMsRvjvMtgUFHBseZxOrX2uKzcRHYMdBlfrqxXDu4DFzcpziNL4YjSFCjLe8lSV/HDi3BEM+MnAKPCeATR3VgdpPhfjCgM70LDQY1lvxLOpjyeXiA/6d5rlXe7h0MM/sRvvLsLdYKKvcZEPzhZUSKTjQ6BK3kElu0XVuReOQKBp3EegW6deU3AECxS5MNg38UjqcqbRGxgSPB2cjHpdEh2sAyr4CtU7hrxU/pJXwTaBalQIL+N014/yRlQTSMX4uVGcqedAkK1MH/YE8dQRF+UUH4B3d+zr25HpnqGkoc49t5LX79LRZ1qBRO3bUkZm1F4Hh14VjWVXQKW6hmXm0WM1OKkJJ23KrNysClyaM+BJ6IkzF9jEV0ugd2nxm9Qb6RL7xowNYVMDyfg9IEsEeG1vTWnmOi3VWR3EzQnZ9blmpXpxDO4fOeTO7CO7ycobuXIrDbqsGrOKdXGnXHn8NmySvXwHvgl6mK5DF2J+YjtFPo7omzVlH56aX53nUBTMyy+z9Gb21YBV4Le7MzmiTUupCzzllD4R+fo1RLe3iGN+W2r1ZBg8FH/pSr97CP9uZellPhD6ZGjPFKNmWB/Hl3VyVhAz2NYgRly4tBkK1cYXVkiBSRA2m9Zj0+f7R/PRhZ3bOEzwLEi9teVAg0vUNZKNizRDBlX+1HZ6FGTd/rM5l05ep3Ps9Sv5/j0XbnZM5U7VGVcIRtFwsuQqfqOfZVTkE iZhbjFUc P9bm1nVdfcIjPHz3XC8f0hlKw+VvGRz32YAG3S4BOmCqAsMo38Nu0Z7ka3UW8SygmXyJ8LXD/5MjfOGBUzRrvi4oLBD2Cm4kBedSsaNZ3HCbTencw2ul906GE0vMGCRFuNQneAnudtJ3atibQeQ36+KzhSVF1gwkdGycHjUeP4omOm112egVMsweo6fmX0Y0oBc12WN7azt3LTTWA6N8/q3RaTLgfrsvfbXunC07Bq2bPBPUfKEglEjv/dMuplLGcwyKdClfgX5/8t+o= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Mon, Nov 02, 2026 at 04:27:30PM +0800, Tiezhu Yang wrote: > The kmalloc_nolock() infrastructure relies on slab caches with double-word > atomic cmpxchg capabilities (__CMPXCHG_DOUBLE). The current inline comment > in __kmalloc_nolock_noprof() uses 'cmpxchg16b' as the prerequisite hardware > capability. > > However, "cmpxchg16b" is an x86-specific instruction mnemonic (CX16). On > modern architectures supported by the Linux kernel, this 128-bit atomic > primitive is satisfied by different hardware implementations: > - arm64: satisfies it via LSE atomics ('casp' instruction) > - s390: satisfies it via native 'cdsg' instruction > - riscv: satisfies it via ZACAS extension ('amocas.q' instruction) > - loongarch: satisfies it via SCQ extension (using an 'll.d'/'sc.q' loop) > > Update the comment to refer to "128-bit atomic cmpxchg" to accurately > describe the cross-platform hardware invariant needed by the lockless > allocator, and to avoid misleading developers of non-x86 archs. Personally, I feel the commit message is a bit lengthy for a simple comment-only patch. It might be better to keep it concise and just directly state the purpose of the change. -- Thanks, Hao