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[ Upstream commit b16ac5bf73 ]
libbpf CI has reported send_signal test is flaky although
I am not able to reproduce it in my local environment.
But I am able to reproduce with on-demand libbpf CI ([1]).
Through code analysis, the following is possible reason.
The failed subtest runs bpf program in softirq environment.
Since bpf_send_signal() only sends to a fork of "test_progs"
process. If the underlying current task is
not "test_progs", bpf_send_signal() will not be triggered
and the subtest will fail.
To reduce the chances where the underlying process is not
the intended one, this patch boosted scheduling priority to
-20 (highest allowed by setpriority() call). And I did
10 runs with on-demand libbpf CI with this patch and I
didn't observe any failures.
[1] https://github.com/libbpf/libbpf/actions/workflows/ondemand.yml
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210817190923.3186725-1-yhs@fb.com
Signed-off-by: Sasha Levin <sashal@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.