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([2a0d:3344:5521:6b10:58fd:68f:7756:389d]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-498011e5edesm46969165e9.2.2026.07.30.03.01.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 30 Jul 2026 03:02:00 -0700 (PDT) Message-ID: <26c1ea30-e6cb-4f3f-ab88-6d00f0ed2117@redhat.com> Date: Thu, 30 Jul 2026 12:01:58 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next v2] rds: synchronize info callbacks with module unload To: Chengfeng Ye , Allison Henderson , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Simon Horman , Santosh Shilimkar , Ka-Cheong Poon , Dan Carpenter Cc: netdev@vger.kernel.org, linux-rdma@vger.kernel.org, rds-devel@oss.oracle.com, linux-kernel@vger.kernel.org References: <20260720184955.3008978-1-nicoyip.dev@gmail.com> <20260727174826.135662-1-nicoyip.dev@gmail.com> From: Paolo Abeni Content-Language: en-US In-Reply-To: <20260727174826.135662-1-nicoyip.dev@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi, It looks like I was too optimistic in my previous reply. On 7/27/26 7:48 PM, Chengfeng Ye wrote: > @@ -78,8 +80,13 @@ void rds_info_register_func(int optname, rds_info_func func) > BUG_ON(optname < RDS_INFO_FIRST || optname > RDS_INFO_LAST); > > spin_lock(&rds_info_lock); > - BUG_ON(rds_info_funcs[offset]); > - rds_info_funcs[offset] = func; > + /* Validate the latest published slot value. */ > + if (WARN_ON_ONCE(smp_load_acquire(&rds_info_funcs[offset]))) { This read is under the same lock that perform the store. It's totally unclear why smp_load_acquire() would be needed here. Very reasonably it's not. > + spin_unlock(&rds_info_lock); > + return; > + } > + /* Pair with lockless callback lookup. */ > + smp_store_release(&rds_info_funcs[offset], func); > spin_unlock(&rds_info_lock); > } > EXPORT_SYMBOL_GPL(rds_info_register_func); > @@ -91,9 +98,15 @@ void rds_info_deregister_func(int optname, rds_info_func func) > BUG_ON(optname < RDS_INFO_FIRST || optname > RDS_INFO_LAST); > > spin_lock(&rds_info_lock); > - BUG_ON(rds_info_funcs[offset] != func); > - rds_info_funcs[offset] = NULL; > + /* Validate the latest published slot value. */ > + if (WARN_ON_ONCE(smp_load_acquire(&rds_info_funcs[offset]) != func)) { Same here. /P