From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5E85F1A7060; Thu, 15 Aug 2024 13:52:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723729952; cv=none; b=PkAP+X2YUwa3R0sP1T8tzXRDpWuckcRYlumXv0bY4nTMcuDmGFhXmsqfTypPmGDOnOs4mIvyVDCCGF2KXL2T/heNO0KU+eX5b2qqcPIqlOsY3gCitQWTaenCFhnG0Evy7U3vmW30NPw5oTyNb4rlxEYteFH5X104I3Y9XhfqJiE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723729952; c=relaxed/simple; bh=DWMmLbXhL0BtzU4iPifABQLVY6weMDMIENDD/YSZBwk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=LVK1iIi85ifK9lDXShxlZ9ZR5UCVXEPDTjYQcuiA4Rbn8P8F/gsLkbwgA4xyBghD4hXdwIskIjoQvdauGUpnUJTdo6AGU0XNKZFS2Bnrme9ZuIjGWhE5I8l5+/q8JLdUrAW80xRtlkPvtizyJmO4TZ+4Rvmy6x32t8mmjzqh//Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=qvS1jQxT; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="qvS1jQxT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 91CA1C4AF0D; Thu, 15 Aug 2024 13:52:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1723729952; bh=DWMmLbXhL0BtzU4iPifABQLVY6weMDMIENDD/YSZBwk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qvS1jQxTtlXyTiChPdd+YGp13qK9hqmFIwVlGXcKNVhPbrbACk2fQ+YHK7x5YdkPp /TfOgjVpR2ZKVLMZ+hedrLKT/rPi8srR2QNeWR6rodaUDVMigf0MVDWEiQkIhhGHrJ 1lsALOSL8w8dQRkn+1O1V1sNSNdw1wahKTj5DqWM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Julian Orth , Pavel Begunkov , Jens Axboe Subject: [PATCH 5.15 258/484] io_uring/io-wq: limit retrying worker initialisation Date: Thu, 15 Aug 2024 15:21:56 +0200 Message-ID: <20240815131951.367500228@linuxfoundation.org> X-Mailer: git-send-email 2.46.0 In-Reply-To: <20240815131941.255804951@linuxfoundation.org> References: <20240815131941.255804951@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Pavel Begunkov commit 0453aad676ff99787124b9b3af4a5f59fbe808e2 upstream. 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 would with the following patch executing task_work in the freezer's 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 Link: https://lore.kernel.org/r/8280436925db88448c7c85c6656edee1a43029ea.1720634146.git.asml.silence@gmail.com Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- io_uring/io-wq.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) --- a/io_uring/io-wq.c +++ b/io_uring/io-wq.c @@ -19,6 +19,7 @@ #include "io-wq.h" #define WORKER_IDLE_TIMEOUT (5 * HZ) +#define WORKER_INIT_LIMIT 3 enum { IO_WORKER_F_UP = 1, /* up and active */ @@ -54,6 +55,7 @@ struct io_worker { unsigned long create_state; struct callback_head create_work; int create_index; + int init_retries; union { struct rcu_head rcu; @@ -732,7 +734,7 @@ static bool io_wq_work_match_all(struct 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 @@ -740,6 +742,8 @@ static inline bool io_should_retry_threa */ if (fatal_signal_pending(current)) return false; + if (worker->init_retries++ >= WORKER_INIT_LIMIT) + return false; switch (err) { case -EAGAIN: @@ -766,7 +770,7 @@ static void create_worker_cont(struct ca io_init_new_worker(wqe, 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_wqe_acct *acct = io_wqe_get_acct(worker); atomic_dec(&acct->nr_running); @@ -831,7 +835,7 @@ fail: tsk = create_io_thread(io_wqe_worker, worker, wqe->node); if (!IS_ERR(tsk)) { io_init_new_worker(wqe, 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 {