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.