linux.git/tools/tracing/rtla/src/common.c, branch v7.1

rtla: Fix parsing of multi-character short options

2026-06-04T08:53:25+00:00

A bug was reported where the parsing of multi-character short options,
be it a short option with an argument specified without space (e.g.
"-p100") or multiple short options in one argument (e.g. -un), ignores
options specific to individual tools.

Furthermore, if the rest of the option is supposed to be an argument, it
gets reinterpreted as a string of options. For example, -p100 gets
interpreted as -100, which is due to hackish implementation read as
--no-thread --no-irq --no-irq with timerlat hist, causing rtla to error
out:

$ rtla timerlat hist -p100
no-irq and no-thread set, there is nothing to do here

This behavior is caused by getopt_long() being called twice on each
argument, once in common_parse_options(), once in [tool]_parse_args():

- common_parse_options() calls getopt_long() with an array of options
  common for all rtla tools, while suppressing errors (opterr = 0).
- If the option fails to parse, common_parse_options() returns 0.
- If 0 is returned from common_parse_options(), [tool]_parse_args()
  calls getopt_long() again, with its own set of options.

* [tool] means one of {osnoise,timerlat}_{top,hist}

At least in glibc, getopt_long() increments its internal nextchar
variable even if the option is not recognized. That means that in the
case of "-p100", common_parse_options() sets nextchar pointing to '1',
and timerlat_hist_parse_args() sees '1', not 'p'; the same then repeats
for the first and second '0'.

As there is no way to restore the correct internal state of
getopt_long() reliably, fix the issue by merging the common options back
to the longopt array and option string of the [tool]_parse_args()
functions using a macro; only the switch part is left in the original
function, which is renamed to set_common_option().

Fixes: 850cd24cb6d6 ("tools/rtla: Add common_parse_options()")
Reported-by: John Kacur 
Tested-by: John Kacur 
Link: https://lore.kernel.org/r/20260602125506.3325345-1-tglozar@redhat.com
Signed-off-by: Tomas Glozar

rtla: Fix segfault on multiple SIGINTs

2026-03-20T13:41:36+00:00

Detach stop_trace() from SIGINT/SIGALRM on tool clean-up to prevent it
from crashing RTLA by accessing freed memory.

This prevents a crash when multiple SIGINTs are received.

Fixes: d6899e560366 ("rtla/timerlat_hist: Abort event processing on second signal")
Fixes: 80967b354a76 ("rtla/timerlat_top: Abort event processing on second signal")
Reviewed-by: Wander Lairson Costa 
Link: https://lore.kernel.org/r/20260310160725.144443-1-tglozar@redhat.com
Signed-off-by: Tomas Glozar

rtla: Handle pthread_create() failure properly

2026-03-11T14:29:50+00:00

Add proper error handling when pthread_create() fails to create the
timerlat user-space dispatcher thread. Previously, the code only logged
an error message but continued execution, which could lead to undefined
behavior when the tool later expects the thread to be running.

When pthread_create() returns an error, the function now jumps to the
out_trace error path to properly clean up resources and exit. This
ensures consistent error handling and prevents the tool from running
in an invalid state without the required user-space thread.

Signed-off-by: Wander Lairson Costa 
Link: https://lore.kernel.org/r/20260309195040.1019085-10-wander@redhat.com
Signed-off-by: Tomas Glozar

rtla: Introduce common_threshold_handler() helper

2026-03-10T09:32:37+00:00

Several functions duplicate the logic for handling threshold actions.
When a threshold is reached, these functions stop the trace, perform
configured actions, and restart the trace if --on-threshold continue
is set.

Create common_threshold_handler() to centralize this shared logic and
avoid code duplication. The function executes the configured threshold
actions and restarts the necessary trace instances when appropriate.

Also add should_continue_tracing() helper to encapsulate the check
for whether tracing should continue after a threshold event, improving
code readability at call sites.

In timerlat_top_bpf_main_loop(), use common_params directly instead
of casting through timerlat_params when only common fields are needed.

Signed-off-by: Wander Lairson Costa 
Link: https://lore.kernel.org/r/20260309195040.1019085-5-wander@redhat.com
Signed-off-by: Tomas Glozar

tools/rtla: Consolidate nr_cpus usage across all tools

2026-03-09T07:49:16+00:00

sysconf(_SC_NPROCESSORS_CONF) (via get_nprocs_conf) reflects
cpu_possible_mask, which is fixed at boot time, so querying it
repeatedly is unnecessary.

Replace multiple calls to sysconf(_SC_NPROCESSORS_CONF) with a single
global nr_cpus variable initialized once at startup.

`#pragma once` in timerlat_u.h is needed for pre-C23 compilers to avoid
redefinition errors.

Signed-off-by: Costa Shulyupin 
Link: https://lore.kernel.org/r/20260306194953.2511960-2-costa.shul@redhat.com
Signed-off-by: Tomas Glozar

tools/rtla: Generate optstring from long options

2026-03-02T13:53:41+00:00

getopt_long() processes short and long options independently.
RTLA, like the majority of applications, uses both short and long
variants for each logical option.

Since the val member of struct option holds the letter of the short
variant, the string of short options can be reconstructed from the
array of long options.

Add getopt_auto() to generate optstring from an array of long options,
eliminating the need to maintain separate short option strings.

Signed-off-by: Costa Shulyupin 
Reviewed-by: Wander Lairson Costa 
Link: https://lore.kernel.org/r/20260108095011.2115719-1-costa.shul@redhat.com
Signed-off-by: Tomas Glozar

rtla: Make stop_tracing variable volatile

2026-01-07T14:57:55+00:00

The stop_tracing global variable is accessed from both the signal
handler context and the main program flow without synchronization.
This creates a potential race condition where compiler optimizations
could cache the variable value in registers, preventing the signal
handler's updates from being visible to other parts of the program.

Add the volatile qualifier to stop_tracing in both common.c and
common.h to ensure all accesses to this variable bypass compiler
optimizations and read directly from memory. This guarantees that
when the signal handler sets stop_tracing, the change is immediately
visible to the main program loop, preventing potential hangs or
delayed shutdown when termination signals are received.

Signed-off-by: Wander Lairson Costa 
Link: https://lore.kernel.org/r/20260106133655.249887-16-wander@redhat.com
Signed-off-by: Tomas Glozar

tools/rtla: Consolidate -H/--house-keeping option parsing

2026-01-07T14:57:17+00:00

Each rtla tool duplicates parsing of -H/--house-keeping.

Migrate the option parsing from individual tools to the
common_parse_options().

Signed-off-by: Costa Shulyupin 
Link: https://lore.kernel.org/r/20251209100047.2692515-8-costa.shul@redhat.com
Signed-off-by: Tomas Glozar

tools/rtla: Consolidate -P/--priority option parsing

2026-01-07T14:57:17+00:00

Each rtla tool duplicates parsing of -P/--priority.

Migrate the option parsing from individual tools to the
common_parse_options().

Signed-off-by: Costa Shulyupin 
Link: https://lore.kernel.org/r/20251209100047.2692515-7-costa.shul@redhat.com
Signed-off-by: Tomas Glozar

tools/rtla: Consolidate -e/--event option parsing

2026-01-07T14:57:17+00:00

Each rtla tool duplicates parsing of -e/--event.

Migrate the option parsing from individual tools to the
common_parse_options().

Signed-off-by: Costa Shulyupin 
Link: https://lore.kernel.org/r/20251209100047.2692515-6-costa.shul@redhat.com
Signed-off-by: Tomas Glozar