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Vast majority of threads don't have any seccomp filters, all while the lock taken here is shared between all threads in given process and frequently used. Safety of the check relies on the following: - seccomp_filter_release is only legally called for PF_EXITING threads - SIGNAL_GROUP_EXIT is only ever set with the sighand lock held - PF_EXITING is only ever set with the sighand lock held *or* after SIGNAL_GROUP_EXIT is set *or* the process is single-threaded - seccomp_sync_threads holds the sighand lock and skips all threads if SIGNAL_GROUP_EXIT is set, PF_EXITING threads if not Resulting reduction of contention gives me a 5% boost in a microbenchmark spawning and killing threads within the same process. Signed-off-by: Mateusz Guzik <mjguzik@gmail.com> Link: https://lore.kernel.org/r/20250213170911.1140187-1-mjguzik@gmail.com Signed-off-by: Kees Cook <kees@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.