From patchwork Fri Jun 16 15:27:31 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bin Meng X-Patchwork-Id: 13282890 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 78F3CEB64D8 for ; Fri, 16 Jun 2023 15:29:34 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qABOA-00079l-P2; Fri, 16 Jun 2023 11:29:26 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qABO5-0006eK-0I for qemu-devel@nongnu.org; Fri, 16 Jun 2023 11:29:21 -0400 Received: from bg4.exmail.qq.com ([43.155.67.158]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qABO3-0000x4-2R for qemu-devel@nongnu.org; Fri, 16 Jun 2023 11:29:20 -0400 X-QQ-mid: bizesmtp84t1686929260tuaizq5u Received: from ubuntu.. ( [111.196.130.174]) by bizesmtp.qq.com (ESMTP) with id ; Fri, 16 Jun 2023 23:27:37 +0800 (CST) X-QQ-SSF: 01200000000000E0G000000A0000000 X-QQ-FEAT: 3M0okmaRx3hOczSSgobv3atsboJvVmW0y1/dlpyRhGnE3hhqNL1E0n/rfO7fY 0jDD9C+mlJum3zX54r8o9aSzYd0NG4IoWWegIa8+YzbYS8JjjSrwdWksXuxdBpTTkHt4jgT WV6Kr070NVBcD194qTIqWltZ+tXKyD3ZizUXIc4KMWGp0OnmrZQ2wwORwrnW4yBebycBJ1t qgZ4mqCFvD0x/j+fvYfmyBfrbgmBY+uU7gmy3MJ322SufiULoojs3QFLED/KBRwOflLKK2I gKE1CBkhswNFSDE6n6lP+8K+tHm69lh0UugEvQN+aJfJAaaEn4PexSc0dCJirsNzy2NCukb B/2A6kf2Za1IHMHlmIA+8+GmkwkULfQeUbzHRRn X-QQ-GoodBg: 0 X-BIZMAIL-ID: 5602026970593767646 From: Bin Meng To: qemu-devel@nongnu.org Cc: Zhangjin Wu , Claudio Imbrenda , David Hildenbrand , "Edgar E. Iglesias" , Jason Wang , Kevin Wolf , =?utf-8?q?Marc-Andr=C3=A9_Lureau?= , Markus Armbruster , "Michael S. Tsirkin" , Nikita Ivanov , Paolo Bonzini , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= , Thomas Huth , Xuzhou Cheng Subject: [PATCH v2 0/6] net/tap: Fix QEMU frozen issue when the maximum number of file descriptors is very large Date: Fri, 16 Jun 2023 23:27:31 +0800 Message-Id: <20230616152737.23545-1-bmeng@tinylab.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-QQ-SENDSIZE: 520 Feedback-ID: bizesmtp:tinylab.org:qybglogicsvrgz:qybglogicsvrgz7a-0 Received-SPF: pass client-ip=43.155.67.158; envelope-from=bmeng@tinylab.org; helo=bg4.exmail.qq.com X-Spam_score_int: -17 X-Spam_score: -1.8 X-Spam_bar: - X-Spam_report: (-1.8 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, RCVD_IN_SBL=0.141, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Current codes using a brute-force traversal of all file descriptors do not scale on a system where the maximum number of file descriptors is set to a very large value (e.g.: in a Docker container of Manjaro distribution it is set to 1073741816). QEMU just looks frozen during start-up. The close-on-exec flag (O_CLOEXEC) was introduced since Linux kernel 2.6.23, FreeBSD 8.3, OpenBSD 5.0, Solaris 11. While it's true QEMU doesn't need to manually close the fds for child process as the proper O_CLOEXEC flag should have been set properly on files with its own codes, QEMU uses a huge number of 3rd party libraries and we don't trust them to reliably be using O_CLOEXEC on everything they open. Modern Linux and BSDs have the close_range() call we can use to do the job, and on Linux we have one more way to walk through /proc/self/fd to complete the task efficiently, which is what qemu_close_range() does, a new API we add in utils/osdep.c. Changes in v2: - Change to use qemu_close_range() to close fds for child process efficiently - v1 link: https://lore.kernel.org/qemu-devel/20230406112041.798585-1-bmeng@tinylab.org/ Bin Meng (4): tests/tcg/cris: Fix the coding style tests/tcg/cris: Correct the off-by-one error util/async-teardown: Fall back to close fds one by one utils/osdep: Introduce qemu_close_range() Zhangjin Wu (2): util/async-teardown: Use qemu_close_range() to close fds net: tap: Use qemu_close_range() to close fds include/qemu/osdep.h | 1 + net/tap.c | 23 ++++++------ tests/tcg/cris/libc/check_openpf5.c | 57 ++++++++++++++--------------- util/async-teardown.c | 37 +------------------ util/osdep.c | 47 ++++++++++++++++++++++++ 5 files changed, 87 insertions(+), 78 deletions(-)