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[72.132.29.68]) by smtp.gmail.com with ESMTPSA id q23-20020aa78437000000b00574679561b9sm3300179pfn.63.2022.11.25.08.51.48 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 25 Nov 2022 08:51:48 -0800 (PST) Message-ID: <93a72543-80b9-7412-61f9-9c28be9ec18e@kernel.dk> Date: Fri, 25 Nov 2022 09:51:47 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:102.0) Gecko/20100101 Thunderbird/102.5.0 Content-Language: en-US To: io-uring From: Jens Axboe Subject: [PATCH v2] io_uring: clear TIF_NOTIFY_SIGNAL if set and task_work not available Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org If we have io-wq or SQPOLL setting the task_work notify signal but the task itself doesn't have task_work to process, we don't clear the flag and hence will enter a repeated check loop if we're waiting on events or file/buf references to go away. This was introduced in a recent patch which eliminated gating the task_work run on just that flag, but that fix meant that we know don't clear the flag if the task itsel doesn't have task_work to run. Cc: stable@vger.kernel.org Fixes: 46a525e199e4 ("io_uring: don't gate task_work run on TIF_NOTIFY_SIGNAL") Signed-off-by: Jens Axboe --- V2 - Add comment - Keep the clear-if-set logic, just move it outside the tw check diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h index cef5ff924e63..a70f8ec88bf3 100644 --- a/io_uring/io_uring.h +++ b/io_uring/io_uring.h @@ -238,9 +238,16 @@ static inline unsigned int io_sqring_entries(struct io_ring_ctx *ctx) static inline int io_run_task_work(void) { + /* + * Always check-and-clear the task_work notification signal. The + * current task may have it set if io-wq or SQPOLL sets it, but not + * have any task_work itself. This can prevent the current task from + * waiting on events efficiently, as interruptible sleeps will turn + * into busy loops. + */ + if (test_thread_flag(TIF_NOTIFY_SIGNAL)) + clear_notify_signal(); if (task_work_pending(current)) { - if (test_thread_flag(TIF_NOTIFY_SIGNAL)) - clear_notify_signal(); __set_current_state(TASK_RUNNING); task_work_run(); return 1;