kernel/linux
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ synced 2026-10-22 19:14:51 +00:00
Code Issues Releases Packages Activity
linux/tools/tracing/rtla
History
Tomas Glozar fafb66e590 rtla/timerlat_top: Fix on-threshold actions firing on signal 
A bug was reported when rtla-timerlat-top tool performs on-threshold
actions, even though no threshold was hit. This is reproduced even if no
threshold is set at all:

$ rtla timerlat top -q -c 0 --on-threshold shell,command='echo BAD'
BAD
                                     Timer Latency
...

The bug is due to incorrect logic in timerlat_top_bpf_main_loop().
The loop uses timerlat_bpf_wait(), the return values of which are:

- > 0 (number of ringbuffer entries): at least 1 CPU hit threshold
- = 0: time out
- < 0: wait was interrupted by a signal

Commit 3138df6f0c ("rtla/timerlat: Exit top main loop on any non-zero
wait_retval") changed the condition for "threshold hit" from
"wait_reval == 1" (exactly 1 CPU hit threshold) to "wait_retval != 0",
to fix a race where multiple CPUs hit the threshold at the same time.

That also made it incorrectly include a signal (< 0), coming from either
duration expired (SIGALRM) or user interrupt (SIGINT).

Check for wait_retval greater than zero in the if condition to cover all
return values correctly.

Fixes: 3138df6f0c ("rtla/timerlat: Exit top main loop on any non-zero wait_retval")
Reported-by: Attila Fazekas <afazekas@redhat.com>
Reviewed-by: Wander Lairson Costa <wander@redhat.com>
Link: https://lore.kernel.org/r/20260713141047.687877-1-tglozar@redhat.com
Signed-off-by: Tomas Glozar <tglozar@redhat.com>
History 2026-07-21 15:42:08 +02:00
..
example rtla/timerlat: Add example for BPF action program 2026-01-07 15:57:16 +01:00
src rtla/timerlat_top: Fix on-threshold actions firing on signal 2026-07-21 15:42:08 +02:00
tests rtla/tests: Fix pgrep filter in get_workload_pids.sh 2026-06-17 16:26:44 +02:00
.gitignore rtla: Fix and clean up .gitignore 2026-06-17 16:26:44 +02:00
Build tools/rtla: Add unit tests for utils.c 2026-03-04 15:51:56 +01:00
Makefile rtla: Also link in ctype.c 2026-07-08 10:38:18 +02:00
Makefile.config tools/rtla: Add unit tests for utils.c 2026-03-04 15:51:56 +01:00
Makefile.rtla tools/rtla: Fix unassigned nr_cpus 2025-11-20 13:15:54 +01:00
Makefile.standalone tools/rtla: Use tools/build makefiles to build rtla 2024-03-20 05:39:06 +01:00
README.txt rtla: Document tests in README 2026-05-29 09:40:54 +02:00

README.txt 

RTLA: Real-Time Linux Analysis tools

The rtla meta-tool includes a set of commands that aims to analyze
the real-time properties of Linux. Instead of testing Linux as a black box,
rtla leverages kernel tracing capabilities to provide precise information
about the properties and root causes of unexpected results.

Installing RTLA

RTLA depends on the following libraries and tools:

 - libtracefs
 - libtraceevent
 - libcpupower (optional, for --deepest-idle-state)
 - libcheck (optional, for unit tests)

For BPF sample collection support, the following extra dependencies are
required:

 - libbpf 1.0.0 or later
 - bpftool with skeleton support
 - clang with BPF CO-RE support

It also depends on python3-docutils to compile man pages.

For development, we suggest the following steps for compiling rtla:

  $ git clone git://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git
  $ cd libtraceevent/
  $ make
  $ sudo make install
  $ cd ..
  $ git clone git://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git
  $ cd libtracefs/
  $ make
  $ sudo make install
  $ cd ..
  $ cd $libcpupower_src
  $ make
  $ sudo make install
  $ cd $rtla_src
  $ make
  $ sudo make install

Running tests

RTLA has two test suites: a runtime test suite and a unit test suite.

The runtime test suite is available as "make check" (root required) and has
the following dependencies, in addition to RTLA build dependencies:

- Perl
- Test::Harness (libtest-harness-perl on Debian/Ubuntu, perl-Test-Harness on Fedora/RHEL)
- bash
- coreutils
- ldd
- util-linux
- procps(-ng)
- bpftool (if rtla is built against libbpf)

as well as the following required system configuration:

- CONFIG_OSNOISE_TRACER=y
- CONFIG_TIMERLAT_TRACER=y
- tracefs mounted and readable at /sys/kernel/tracing

The unit test suite is available as "make unit-tests" and has the following
dependencies:

- libcheck

Unlike the runtime test suite, root is not required to run unit tests, nor is
a tracefs/osnoise/timerlat-capable kernel required.

For further information, please refer to the rtla man page.