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628e124404
The test might fail on the Arm64 platform with the error:
# perf test -vvv "Track with sched_switch"
Missing sched_switch events
#
The issue is caused by incorrect handling of timestamp comparisons. The
comparison result, a signed 64-bit value, was being directly cast to an
int, leading to incorrect sorting for sched events.
The case does not fail everytime, usually I can trigger the failure
after run 20 ~ 30 times:
# while true; do perf test "Track with sched_switch"; done
106: Track with sched_switch : Ok
106: Track with sched_switch : Ok
106: Track with sched_switch : Ok
106: Track with sched_switch : Ok
106: Track with sched_switch : Ok
106: Track with sched_switch : Ok
106: Track with sched_switch : Ok
106: Track with sched_switch : Ok
106: Track with sched_switch : Ok
106: Track with sched_switch : Ok
106: Track with sched_switch : Ok
106: Track with sched_switch : Ok
106: Track with sched_switch : Ok
106: Track with sched_switch : Ok
106: Track with sched_switch : FAILED!
106: Track with sched_switch : Ok
106: Track with sched_switch : Ok
106: Track with sched_switch : Ok
106: Track with sched_switch : Ok
106: Track with sched_switch : Ok
106: Track with sched_switch : Ok
106: Track with sched_switch : Ok
106: Track with sched_switch : Ok
106: Track with sched_switch : FAILED!
106: Track with sched_switch : Ok
106: Track with sched_switch : Ok
I used cross compiler to build Perf tool on my host machine and tested on
Debian / Juno board. Generally, I think this issue is not very specific
to GCC versions. As both internal CI and my local env can reproduce the
issue.
My Host Build compiler:
# aarch64-linux-gnu-gcc --version
aarch64-linux-gnu-gcc (Ubuntu 13.3.0-6ubuntu2~24.04) 13.3.0
Juno Board:
# lsb_release -a
No LSB modules are available.
Distributor ID: Debian
Description: Debian GNU/Linux 12 (bookworm)
Release: 12
Codename: bookworm
Fix this by explicitly returning 0, 1, or -1 based on whether the result
is zero, positive, or negative.
Fixes: d44bc55829 ("perf tests: Add a test for tracking with sched_switch")
Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Leo Yan <leo.yan@arm.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20250331172759.115604-1-leo.yan@arm.com
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
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https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText 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.