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88d706ba7c
Implement queued spin lock algorithm as BPF program for lock words living in BPF arena. The algorithm is copied from kernel/locking/qspinlock.c and adapted for BPF use. We first implement abstract helpers for portable atomics and acquire/release load instructions, by relying on X86_64 presence to elide expensive barriers and rely on implementation details of the JIT, and fall back to slow but correct implementations elsewhere. When support for acquire/release load/stores lands, we can improve this state. Then, the qspinlock algorithm is adapted to remove dependence on multi-word atomics due to lack of support in BPF ISA. For instance, xchg_tail cannot use 16-bit xchg, and needs to be a implemented as a 32-bit try_cmpxchg loop. Loops which are seemingly infinite from verifier PoV are annotated with cond_break_label macro to return an error. Only 1024 NR_CPUs are supported. Note that the slow path is a global function, hence the verifier doesn't know the return value's precision. The recommended way of usage is to always test against zero for success, and not ret < 0 for error, as the verifier would assume ret > 0 has not been accounted for. Add comments in the function documentation about this quirk. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20250306035431.2186189-3-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.