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Wed, 03 Sep 2025 16:16:41 -0700 (PDT) Received: from [172.20.0.68] ([70.88.81.106]) by smtp.gmail.com with ESMTPSA id e9e14a558f8ab-3f65c076d97sm18857345ab.19.2025.09.03.16.16.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 03 Sep 2025 16:16:40 -0700 (PDT) Message-ID: <51277999-41ec-45ad-a074-2352f46c882e@kernel.dk> Date: Wed, 3 Sep 2025 17:16:39 -0600 Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] io_uring: remove WRITE_ONCE() in io_uring_create() To: Caleb Sander Mateos Cc: io-uring@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250902215144.1925256-1-csander@purestorage.com> <28b5e071-70f2-4f46-86af-11879be0f2a4@kernel.dk> Content-Language: en-US From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 9/2/25 9:32 PM, Caleb Sander Mateos wrote: > On Tue, Sep 2, 2025 at 6:20 PM Jens Axboe wrote: >> >> On 9/2/25 3:51 PM, Caleb Sander Mateos wrote: >>> There's no need to use WRITE_ONCE() to set ctx->submitter_task in >>> io_uring_create() since no other thread can access the io_ring_ctx until >>> a file descriptor is associated with it. So use a normal assignment >>> instead of WRITE_ONCE(). >> >> Would probably warrant a code comment to that effect, as just reading >> the code would be slightly confusing after this. > > Could you elaborate on why you find it confusing? I wouldn't expect to > see WRITE_ONCE() or any other atomic operation used when initializing > memory prior to it being made accessible from other threads. It looks > like commit 8579538c89e3 ("io_uring/msg_ring: fix remote queue to > disabled ring") added the WRITE_ONCE() both here and in > io_register_enable_rings(). But it's only needed in > io_register_enable_rings(), where the io_ring_ctx already has an > associated file descriptor and may be accessed concurrently from > multiple threads. Just add simple comment saying something like "No need for a WRITE_ONCE() here, as it's before the ring is visible/enabled". Otherwise I bet I'll be fielding a patch for that in the future. -- Jens Axboe