From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by smtp.lore.kernel.org (Postfix) with ESMTP id DF6FFCD4F3D for ; Thu, 21 May 2026 15:43:59 +0000 (UTC) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 05CAE402A2; Thu, 21 May 2026 17:43:59 +0200 (CEST) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by mails.dpdk.org (Postfix) with ESMTP id 03E2E400D5 for ; Thu, 21 May 2026 17:43:56 +0200 (CEST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 2D33B1C25; Thu, 21 May 2026 08:43:50 -0700 (PDT) Received: from [10.122.53.155] (unknown [10.122.53.155]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 08F2C3F632; Thu, 21 May 2026 08:43:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1779378235; bh=CyYc1WxvqrOTWE1m4lzR7La43Mc0kEnS7fOGn9iEb70=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=rMYiU21LsdwWxuEy+OX0uP6HuFy6Ze+1qw9quz4KNzist3/bJ4UWu2SLiESkUB1fr Ln7tC1w8MWLF1ezJW1WMiZr9DQjyK/dC+90O343DWe5QsjGdh5AIqOgTbI0YLz3imx W6bfYkHUOcmg3m4znrlKXTl2vFPUdDHEo/VYMsPI= Message-ID: Date: Thu, 21 May 2026 10:43:54 -0500 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC 2/7] eal: reimplement rte_smp_*mb with rte_atomic_thread_fence To: Stephen Hemminger , dev@dpdk.org Cc: Bibo Mao , David Christensen , Sun Yuechi , Bruce Richardson , Konstantin Ananyev References: <20260521042043.1590536-1-stephen@networkplumber.org> <20260521042043.1590536-3-stephen@networkplumber.org> Content-Language: en-US From: Wathsala Vithanage In-Reply-To: <20260521042043.1590536-3-stephen@networkplumber.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Hi Stephen, Suggesting minor changes to comments on acquire and release fences.. > +/** @name SMP Memory Barrier > + */ > +///@{ > +/** > + * General memory barrier between lcores > + * > + * Guarantees that the LOAD and STORE operations that precede the > + * rte_smp_mb() call are globally visible across the lcores > + * before the LOAD and STORE operations that follows it. > + */ > +static __rte_always_inline void > +rte_smp_mb(void) > +{ > + rte_atomic_thread_fence(rte_memory_order_seq_cst); > +} > + > +/** > + * Write memory barrier between lcores > + * > + * Guarantees that the STORE operations that precede the > + * rte_smp_wmb() call are globally visible across the lcores > + * before the STORE operations that follows it. > + */ > +static __rte_always_inline void > +rte_smp_wmb(void) > +{ > + rte_atomic_thread_fence(rte_memory_order_release); > +} Release fences order STORE | STORE, and  LOAD | STORE. Therefor, the comment should be "Guarantees that LOAD and STORE operations that precede the rte_smp_wmb() call are globally observed before STORE operations that follows it." > + > +/** > + * Read memory barrier between lcores > + * > + * Guarantees that the LOAD operations that precede the > + * rte_smp_rmb() call are globally visible across the lcores > + * before the LOAD operations that follows it. > + */ > +static __rte_always_inline void > +rte_smp_rmb(void) > +{ > + rte_atomic_thread_fence(rte_memory_order_acquire); > +} Acquire fences order LOAD | LOAD and LOAD | STORE. Thus, the comment should be "Guarantees that the LOAD operations that precede the rte_smp_rmb() call observe global  state before LOAD and STORE operations that follows it" --wathsala