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Fri, 12 Jun 2026 12:37:13 -0700 (PDT) Received: from [192.168.1.150] ([198.8.77.157]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-7e78148a918sm2596110a34.7.2026.06.12.12.37.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 12 Jun 2026 12:37:12 -0700 (PDT) Message-ID: Date: Fri, 12 Jun 2026 13:37:11 -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 4/6] io_uring: switch normal task_work to a mpscq To: Caleb Sander Mateos Cc: io-uring@vger.kernel.org, dvyukov@google.com, krisman@suse.de References: <20260612025125.1690253-1-axboe@kernel.dk> <20260612025125.1690253-5-axboe@kernel.dk> Content-Language: en-US From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/12/26 12:59 PM, Caleb Sander Mateos wrote: >> @@ -236,10 +262,14 @@ void io_req_normal_work_add(struct io_kiocb *req) >> return; >> } >> >> + /* task_work must only be added once */ >> + if (test_and_set_bit(0, &tctx->tw_pending)) >> + return; > > Is tw_pending necessary? How come the task_work_add() exclusivity > isn't already provided by the mpscq_push() check above? It is, because the transition from empty -> not-empty no longer works for that, as the mpscq emtpies one-by-one rather than with a delete-all kind of primitive. I missed that originally and things blew up spectacularly very quickly :-) -- Jens Axboe