On Wed, Jun 28, 2023 at 11:29 PM Bin Meng <bm...@tinylab.org> wrote: > > > 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-bm...@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-bm...@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 >
Ping for 8.1?
