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The perf_buffer fails on system with offline cpus: # test_progs -t perf_buffer serial_test_perf_buffer:PASS:nr_cpus 0 nsec serial_test_perf_buffer:PASS:nr_on_cpus 0 nsec serial_test_perf_buffer:PASS:skel_load 0 nsec serial_test_perf_buffer:PASS:attach_kprobe 0 nsec serial_test_perf_buffer:PASS:perf_buf__new 0 nsec serial_test_perf_buffer:PASS:epoll_fd 0 nsec skipping offline CPU #4 serial_test_perf_buffer:PASS:perf_buffer__poll 0 nsec serial_test_perf_buffer:PASS:seen_cpu_cnt 0 nsec serial_test_perf_buffer:PASS:buf_cnt 0 nsec ... serial_test_perf_buffer:PASS:fd_check 0 nsec serial_test_perf_buffer:PASS:drain_buf 0 nsec serial_test_perf_buffer:PASS:consume_buf 0 nsec serial_test_perf_buffer:FAIL:cpu_seen cpu 5 not seen #88 perf_buffer:FAIL Summary: 0/0 PASSED, 0 SKIPPED, 1 FAILED If the offline cpu is from the middle of the possible set, we get mismatch with possible and online cpu buffers. The perf buffer test calls perf_buffer__consume_buffer for all 'possible' cpus, but the library holds only 'online' cpu buffers and perf_buffer__consume_buffer returns them based on index. Adding extra (online) index to keep track of online buffers, we need the original (possible) index to trigger trace on proper cpu. Signed-off-by: Jiri Olsa <jolsa@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: John Fastabend <john.fastabend@gmail.com> Link: https://lore.kernel.org/bpf/20211021114132.8196-3-jolsa@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.