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[PATCH v4 0/6] net/tap: Fix QEMU frozen issue when the maximum number of
From: |
Bin Meng |
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 |
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(-)
--
2.34.1
- [PATCH v4 0/6] net/tap: Fix QEMU frozen issue when the maximum number of file descriptors is very large,
Bin Meng <=
- [PATCH v4 1/6] tests/tcg/cris: Fix the coding style, Bin Meng, 2023/06/28
- [PATCH v4 2/6] tests/tcg/cris: Correct the off-by-one error, Bin Meng, 2023/06/28
- [PATCH v4 4/6] util/osdep: Introduce qemu_close_range(), Bin Meng, 2023/06/28
- [PATCH v4 6/6] net: tap: Use qemu_close_range() to close fds, Bin Meng, 2023/06/28
- [PATCH v4 3/6] util/async-teardown: Fall back to close fds one by one, Bin Meng, 2023/06/28
- [PATCH v4 5/6] util/async-teardown: Use qemu_close_range() to close fds, Bin Meng, 2023/06/28
- Re: [PATCH v4 0/6] net/tap: Fix QEMU frozen issue when the maximum number of file descriptors is very large, Michael Tokarev, 2023/06/29