From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f42.google.com (mail-ej1-f42.google.com [209.85.218.42]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 069D515279B; Tue, 9 Jul 2024 14:27:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.218.42 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720535239; cv=none; b=T+LP2QPCCMj/Ga7wEBYF+xepYhowro8HHe6Bwuo/XpzoFlGvwcUw8qcMD76xt7ur5F7t6wXAxE9PxYEdVUNhuIcA0cjrYZgC81/JCM4FjSuTdyVHYUvZ6cwdXrZljOfS3YwZJ6XQg4oQul930E3TqfI5X6f5G0wTNV2ACYtC4Ts= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720535239; c=relaxed/simple; bh=P+TJsos0wRuICzWhaMFgjmN4/yDzbtZJ6N0VJY3WNCs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=RvdtDkYW2/EGoPB8p/IRrXEVzob/XD8h5P92cgHrfTxVyxXWbUkFRY8hhZZFJuuZ3qIdQSXcCTTxR9bLROkHbNJGocyN6Cf2f2oaWcajSlNuwuxUw17pQTKXOVniJzt2+wR9IOa3xi+srA3f8k0nJ8z9X0yGqqsQLPcw9CpR5jU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=cldCYRWS; arc=none smtp.client-ip=209.85.218.42 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="cldCYRWS" Received: by mail-ej1-f42.google.com with SMTP id a640c23a62f3a-a77baa87743so564723266b.3; Tue, 09 Jul 2024 07:27:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1720535236; x=1721140036; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=ttgYBK7CIbyCBuvHefwURr58xYqG6L2p5WKp4rRTzQk=; b=cldCYRWSoM/cbqcQ1kJaku6kEA6nXuQAeQVKRoI30PxzX6st9//03XoKAfcEx5bJqB UeWzsquVh2pmNeS0D43fJlIbYHuwm6h7iVzm1ZgMkP5n+eTSCcA0HDeUJFlkqhOgAgOx XEcqjYwZ+VJaWnVs9QDtbroVBoPf8jCaX4nuCiOH9Us5bESP2yvN/qVtP2jy8whWK6tP wuQLdlx6mYVW6NIkfenQw2exFK5tmB+aHvmcxig5nQpRQqrhn1MX3Xyk/okG4iNiHOaa IX3Wlee/Il0zSuTPkEi62+e7/gBy72k6AtiLZOyhgJBL6Xp/QiLsVK734Rgz2PWCkiQ0 dT1g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1720535236; x=1721140036; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=ttgYBK7CIbyCBuvHefwURr58xYqG6L2p5WKp4rRTzQk=; b=XtLUCqM2pOZBvQDHn+5dvPomkFBI1N69bRagLn/70rGrZ0cVts5BFMD+JWbq6Gzvgf nZy7ZKuqGj/4A3OzswwvizfKdD5AMIyGkHY/NrUUEgDbblAk96ax/K6r6OkgeoQYRuk4 c3HkyhcSRdDadjf/2CcGazD7yXh6FzLcUbceO6Lt4h2ur0uK9p8YFNuJAdYoBtU1JFql ulNIwPze5OGpu/23x5yy3+oq7CTtm13VRvMJoGnlTy2aI75ljD3rIMTIoQl6p11wa1X+ C774af78p4Sj9LS+12qI1yCbxzUiQanqc152pyFyqCLP+JbkBWXXAG/0qGIBNenasI6f dKCg== X-Forwarded-Encrypted: i=1; AJvYcCUPKzoaVM4DmfXxWrSINWctvBfdOq4A/Cyng47rZeN3agI6OIl+he81eYyZIXcjwXKQbUyeBBrWF7nGmuwZUPqPVjqJx7CfVdayMhqi X-Gm-Message-State: AOJu0Yy8DfZS/haf3Yj/gW5VGL2+dL6g4qQzR50+ylbw1lqZnE520KN1 e45b1Oxund0v1QXj6DH1ScbWncmNGPH8gLTxCec5EQN3rGrmzNCm35Nfhw== X-Google-Smtp-Source: AGHT+IFnaWqj+voLe/snIcMHRpZCxkD5hkOP3UTwoJHVMVHj1VnGQCWk96AVVhz1D3MWRARgpRaikQ== X-Received: by 2002:a17:906:f592:b0:a77:cf9d:f495 with SMTP id a640c23a62f3a-a780b7010a0mr304952766b.40.1720535235827; Tue, 09 Jul 2024 07:27:15 -0700 (PDT) Received: from 127.0.0.1localhost ([163.114.131.193]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a780a7ff21esm80649966b.135.2024.07.09.07.27.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 09 Jul 2024 07:27:15 -0700 (PDT) From: Pavel Begunkov To: io-uring@vger.kernel.org Cc: Jens Axboe , asml.silence@gmail.com, Oleg Nesterov , Andrew Morton , Christian Brauner , Tycho Andersen , Thomas Gleixner , linux-kernel@vger.kernel.org, Julian Orth , Peter Zijlstra , Tejun Heo Subject: [PATCH v2 1/2] io_uring/io-wq: limit retrying worker initialisation Date: Tue, 9 Jul 2024 15:27:18 +0100 Message-ID: <1af2a697b568f8cf77c5d527d183fa0ffe8fd9cc.1720534425.git.asml.silence@gmail.com> X-Mailer: git-send-email 2.44.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit If io-wq worker creation fails, we retry it by queueing up a task_work. tasK_work is needed because it should be done from the user process context. The problem is that retries are not limited, and if queueing a task_work is the reason for the failure, we might get into an infinite loop. It doesn't seem to happen now but it will with the following patch executing task_work in the freezing loop. For now, arbitrarily limit the number of attempts to create a worker. Cc: stable@vger.kernel.org Fixes: 3146cba99aa28 ("io-wq: make worker creation resilient against signals") Reported-by: Julian Orth Signed-off-by: Pavel Begunkov --- io_uring/io-wq.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c index 913c92249522..f1e7c670add8 100644 --- a/io_uring/io-wq.c +++ b/io_uring/io-wq.c @@ -23,6 +23,7 @@ #include "io_uring.h" #define WORKER_IDLE_TIMEOUT (5 * HZ) +#define WORKER_INIT_LIMIT 3 enum { IO_WORKER_F_UP = 0, /* up and active */ @@ -58,6 +59,7 @@ struct io_worker { unsigned long create_state; struct callback_head create_work; + int init_retries; union { struct rcu_head rcu; @@ -745,7 +747,7 @@ static bool io_wq_work_match_all(struct io_wq_work *work, void *data) return true; } -static inline bool io_should_retry_thread(long err) +static inline bool io_should_retry_thread(struct io_worker *worker, long err) { /* * Prevent perpetual task_work retry, if the task (or its group) is @@ -753,6 +755,8 @@ static inline bool io_should_retry_thread(long err) */ if (fatal_signal_pending(current)) return false; + if (worker->init_retries++ >= WORKER_INIT_LIMIT) + return false; switch (err) { case -EAGAIN: @@ -779,7 +783,7 @@ static void create_worker_cont(struct callback_head *cb) io_init_new_worker(wq, worker, tsk); io_worker_release(worker); return; - } else if (!io_should_retry_thread(PTR_ERR(tsk))) { + } else if (!io_should_retry_thread(worker, PTR_ERR(tsk))) { struct io_wq_acct *acct = io_wq_get_acct(worker); atomic_dec(&acct->nr_running); @@ -846,7 +850,7 @@ static bool create_io_worker(struct io_wq *wq, int index) tsk = create_io_thread(io_wq_worker, worker, NUMA_NO_NODE); if (!IS_ERR(tsk)) { io_init_new_worker(wq, worker, tsk); - } else if (!io_should_retry_thread(PTR_ERR(tsk))) { + } else if (!io_should_retry_thread(worker, PTR_ERR(tsk))) { kfree(worker); goto fail; } else { -- 2.44.0