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( [111.196.130.174]) by bizesmtp.qq.com (ESMTP) with id ; Wed, 28 Jun 2023 23:27:27 +0800 (CST) X-QQ-SSF: 01200000000000E0G000000A0000000 X-QQ-FEAT: SFhf6fKhx/9iz4DBPKS36ENBTcBPb7Sd+FeFBYFVw89EUrka8PXJd4mZlperZ ZYtmWIDxQH0Q0xbH7m2DtBUZZ1z88SLAkEHCXL02D2BwGM9mRgGdxSzKHe7j+xkszzdB5iQ B3hzeHdLvkh55ScqkrxqO8RkER2O3EIrwJwqwxYeCXCIAgadW4Grml/kIAijklBRh6w7rz+ LKnDNiSkiXjGGgbyjBELjjZkq/jh7NTvxuckSLAyYP70aX8HScMSoAS3oosfZYGn1Wjc7dS CuZrMeD1FIcO1+cn5jt6mcY0QyuJ6Ym2d0Oinn5g7/QYoRbQKtGYBRBJHHGaKTQTii7Yofe 1YO7rs0OdT0IejnTreS8p9trjOGv0ZkuBJ5A7+foo6putKODbCEZwSdY4nJbg== X-QQ-GoodBg: 0 X-BIZMAIL-ID: 5553759802645831184 From: Bin Meng To: qemu-devel@nongnu.org Cc: Richard Henderson , Zhangjin Wu , Claudio Imbrenda , =?utf-8?q?Daniel_P=2E_Berrang=C3=A9?= , "Edgar E. Iglesias" , Jason Wang , Kevin Wolf , =?utf-8?q?Marc-Andr=C3=A9_Lureau?= , "Michael S. Tsirkin" , Paolo Bonzini , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= , Thomas Huth , Xuzhou Cheng Subject: [PATCH v4 0/6] net/tap: Fix QEMU frozen issue when the maximum number of file descriptors is very large Date: Wed, 28 Jun 2023 23:27:20 +0800 Message-Id: <20230628152726.110295-1-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=43.154.221.58; 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_H4=0.001, RCVD_IN_MSPIKE_WL=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 util/osdep.c. V1 link: https://lore.kernel.org/qemu-devel/20230406112041.798585-1-bmeng@tinylab.org/ Changes in v4: - add 'first > last' check logic - reorder the ifdefs logic - change i to unsigned int type - use qemu_strtoi() instead of atoi() - limit last upper value to sysconf(_SC_OPEN_MAX) - 1 - call sysconf directly instead of using a variable - put fd on its own line Changes in v3: - fix win32 build failure - limit the last_fd of qemu_close_range() to sysconf(_SC_OPEN_MAX) Changes in v2: - new patch: "tests/tcg/cris: Fix the coding style" - new patch: "tests/tcg/cris: Correct the off-by-one error" - new patch: "util/async-teardown: Fall back to close fds one by one" - new patch: "util/osdep: Introduce qemu_close_range()" - new patch: "util/async-teardown: Use qemu_close_range() to close fds" - 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 util/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 | 24 ++++++------ tests/tcg/cris/libc/check_openpf5.c | 57 +++++++++++++-------------- util/async-teardown.c | 37 +----------------- util/osdep.c | 60 +++++++++++++++++++++++++++++ 5 files changed, 101 insertions(+), 78 deletions(-)