rtla/timerlat_hist: Set OSNOISE_WORKLOAD for kernel threads

commit d8d866171a414ed88bd0d720864095fd75461134 upstream.

When using rtla timerlat with userspace threads (-u or -U), rtla
disables the OSNOISE_WORKLOAD option in
/sys/kernel/tracing/osnoise/options. This option is not re-enabled in a
subsequent run with kernel-space threads, leading to rtla collecting no
results if the previous run exited abnormally:

$ rtla timerlat hist -u
^\Quit (core dumped)
$ rtla timerlat hist -k -d 1s
Index
over:
count:
min:
avg:
max:
ALL:        IRQ       Thr       Usr
count:        0         0         0
min:          -         -         -
avg:          -         -         -
max:          -         -         -

The issue persists until OSNOISE_WORKLOAD is set manually by running:
$ echo OSNOISE_WORKLOAD > /sys/kernel/tracing/osnoise/options

Set OSNOISE_WORKLOAD when running rtla with kernel-space threads if
available to fix the issue.

Cc: stable@vger.kernel.org
Cc: John Kacur <jkacur@redhat.com>
Cc: Luis Goncalves <lgoncalv@redhat.com>
Link: https://lore.kernel.org/20250107144823.239782-3-tglozar@redhat.com
Fixes: ed774f7481fa ("rtla/timerlat_hist: Add timerlat user-space support")
Signed-off-by: Tomas Glozar <tglozar@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
[ params->kernel_workload does not exist in 6.6, use
!params->user_hist ]
Signed-off-by: Tomas Glozar <tglozar@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/tools/tracing/rtla/src/timerlat_hist.c b/tools/tracing/rtla/src/timerlat_hist.c
index ab13a9392bff62ffe73951717a4f13747ef7a89c..198cdf75c837bb5baef4194eeeb09b1f68e54197 100644 (file)
--- a/tools/tracing/rtla/src/timerlat_hist.c
+++ b/tools/tracing/rtla/src/timerlat_hist.c
@@ -900,12 +900,15 @@ timerlat_hist_apply_config(struct osnoise_tool *tool, struct timerlat_hist_param
                auto_house_keeping(&params->monitored_cpus);
        }
 
-       if (params->user_hist) {
-               retval = osnoise_set_workload(tool->context, 0);
-               if (retval) {
-                       err_msg("Failed to set OSNOISE_WORKLOAD option\n");
-                       goto out_err;
-               }
+       /*
+       * Set workload according to type of thread if the kernel supports it.
+       * On kernels without support, user threads will have already failed
+       * on missing timerlat_fd, and kernel threads do not need it.
+       */
+       retval = osnoise_set_workload(tool->context, !params->user_hist);
+       if (retval < -1) {
+               err_msg("Failed to set OSNOISE_WORKLOAD option\n");
+               goto out_err;
        }
 
        return 0;