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c940fa276b
In most configurations, it works well with skipping 4 entries by
default. If some systems still have 3 BPF internal stack frames,
the next frame should be in a lock function which will be skipped
later when it tries to find a caller. So increasing to 4 won't
affect such systems too.
With --stack-skip=0, I can see something like this:
24 49.84 us 7.41 us 2.08 us mutex bpf_prog_e1b85959d520446c_contention_begin+0x12e
0xffffffffc045040e bpf_prog_e1b85959d520446c_contention_begin+0x12e
0xffffffffc045040e bpf_prog_e1b85959d520446c_contention_begin+0x12e
0xffffffff82ea2071 bpf_trace_run2+0x51
0xffffffff82de775b __bpf_trace_contention_begin+0xb
0xffffffff82c02045 __mutex_lock+0x245
0xffffffff82c019e3 __mutex_lock_slowpath+0x13
0xffffffff82c019c0 mutex_lock+0x20
0xffffffff830a083c kernfs_iop_permission+0x2c
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <song@kernel.org>
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20221028180128.3311491-5-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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.