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Martin KaFai Lau
23d86c8e02
Hou Tao says: ==================== From: Hou Tao <houtao1@huawei.com> Hi, The patchset aims to make the update of per-cpu prog->active and per-cpu bpf_task_storage_busy being preemption-safe. The problem is on same architectures (e.g. arm64), __this_cpu_{inc|dec|inc_return} are neither preemption-safe nor IRQ-safe, so under fully preemptible kernel the concurrent updates on these per-cpu variables may be interleaved and the final values of these variables may be not zero. Patch 1 & 2 use the preemption-safe per-cpu helpers to manipulate prog->active and bpf_task_storage_busy. Patch 3 & 4 add a test case in map_tests to show the concurrent updates on the per-cpu bpf_task_storage_busy by using __this_cpu_{inc|dec} are not atomic. Comments are always welcome. Regards, Tao Change Log: v2: * Patch 1: update commit message to indicate the problem is only possible for fully preemptible kernel * Patch 2: a new patch which fixes the problem for prog->active * Patch 3 & 4: move it to test_maps and make it depend on CONFIG_PREEMPT v1: https://lore.kernel.org/bpf/20220829142752.330094-1-houtao@huaweicloud.com/ ==================== Signed-off-by: Martin KaFai Lau <martin.lau@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 Restructured Text 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.