From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 52F5EC433E0 for ; Tue, 7 Jul 2020 15:30:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3075A204EC for ; Tue, 7 Jul 2020 15:30:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594135835; bh=2ZNNi2geWKQy6z4LM6BHlQI2VVnnJCfcD3MR22KGryc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=SEALM9IVukRvNW4wnKxDV58ofNSQaNmyZVOdOWd3JS/ZI3VQhI89FAke9vX5uOmBM LOvc9I3mQVPA7N63v7FAWlFQ3de7QUgdrTa6x4O7k7KEWQwW19NAfMJsvDqNUmZ1wb IWRqcTO8VNmyXZ7CIR8Ht6NB1juDzcqPud9gnpCk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730182AbgGGPac (ORCPT ); Tue, 7 Jul 2020 11:30:32 -0400 Received: from mail.kernel.org ([198.145.29.99]:37754 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730048AbgGGPYM (ORCPT ); Tue, 7 Jul 2020 11:24:12 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0DD74207D0; Tue, 7 Jul 2020 15:24:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594135452; bh=2ZNNi2geWKQy6z4LM6BHlQI2VVnnJCfcD3MR22KGryc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0s2KL7/RzkEETxZudWzUtJ8oPnk+cVQDDlBFIBgHHvZ1bMQfVheN11r/dh5FIIbSc ylFef4JRHu3l5lU1eKgXqTfWcIRfSqbt4X0rAF58qkqKLfFAbkpjLCj4sFgiZ0+vsQ ijX+1FRInubWhIU805eoZ7+5Xql6i8hnmhTsxyho= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jens Axboe , Sasha Levin Subject: [PATCH 5.7 046/112] io_uring: use signal based task_work running Date: Tue, 7 Jul 2020 17:16:51 +0200 Message-Id: <20200707145803.190649104@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200707145800.925304888@linuxfoundation.org> References: <20200707145800.925304888@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jens Axboe [ Upstream commit ce593a6c480a22acba08795be313c0c6d49dd35d ] Since 5.7, we've been using task_work to trigger async running of requests in the context of the original task. This generally works great, but there's a case where if the task is currently blocked in the kernel waiting on a condition to become true, it won't process task_work. Even though the task is woken, it just checks whatever condition it's waiting on, and goes back to sleep if it's still false. This is a problem if that very condition only becomes true when that task_work is run. An example of that is the task registering an eventfd with io_uring, and it's now blocked waiting on an eventfd read. That read could depend on a completion event, and that completion event won't get trigged until task_work has been run. Use the TWA_SIGNAL notification for task_work, so that we ensure that the task always runs the work when queued. Cc: stable@vger.kernel.org # v5.7 Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- fs/io_uring.c | 32 ++++++++++++++++++++++++-------- 1 file changed, 24 insertions(+), 8 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 71d281f68ed83..51362a619fd50 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -4136,6 +4136,21 @@ struct io_poll_table { int error; }; +static int io_req_task_work_add(struct io_kiocb *req, struct callback_head *cb, + int notify) +{ + struct task_struct *tsk = req->task; + int ret; + + if (req->ctx->flags & IORING_SETUP_SQPOLL) + notify = 0; + + ret = task_work_add(tsk, cb, notify); + if (!ret) + wake_up_process(tsk); + return ret; +} + static int __io_async_wake(struct io_kiocb *req, struct io_poll_iocb *poll, __poll_t mask, task_work_func_t func) { @@ -4159,13 +4174,13 @@ static int __io_async_wake(struct io_kiocb *req, struct io_poll_iocb *poll, * of executing it. We can't safely execute it anyway, as we may not * have the needed state needed for it anyway. */ - ret = task_work_add(tsk, &req->task_work, true); + ret = io_req_task_work_add(req, &req->task_work, TWA_SIGNAL); if (unlikely(ret)) { WRITE_ONCE(poll->canceled, true); tsk = io_wq_get_task(req->ctx->io_wq); - task_work_add(tsk, &req->task_work, true); + task_work_add(tsk, &req->task_work, 0); + wake_up_process(tsk); } - wake_up_process(tsk); return 1; } @@ -6260,19 +6275,20 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, do { prepare_to_wait_exclusive(&ctx->wait, &iowq.wq, TASK_INTERRUPTIBLE); + /* make sure we run task_work before checking for signals */ if (current->task_works) task_work_run(); - if (io_should_wake(&iowq, false)) - break; - schedule(); if (signal_pending(current)) { - ret = -EINTR; + ret = -ERESTARTSYS; break; } + if (io_should_wake(&iowq, false)) + break; + schedule(); } while (1); finish_wait(&ctx->wait, &iowq.wq); - restore_saved_sigmask_unless(ret == -EINTR); + restore_saved_sigmask_unless(ret == -ERESTARTSYS); return READ_ONCE(rings->cq.head) == READ_ONCE(rings->cq.tail) ? ret : 0; } -- 2.25.1