rtla/timerlat_hist: Set OSNOISE_WORKLOAD for kernel threads

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>

diff --git a/tools/tracing/rtla/src/timerlat_hist.c b/tools/tracing/rtla/src/timerlat_hist.c
index 53ded187b33a30353b88db2913e36b4ca08e3d58..d4bd02c01c539540aa88f970dd501600a2b5260c 100644 (file)
--- a/tools/tracing/rtla/src/timerlat_hist.c
+++ b/tools/tracing/rtla/src/timerlat_hist.c
@@ -1085,12 +1085,15 @@ timerlat_hist_apply_config(struct osnoise_tool *tool, struct timerlat_hist_param
                }
        }
 
-       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->kernel_workload);
+       if (retval < -1) {
+               err_msg("Failed to set OSNOISE_WORKLOAD option\n");
+               goto out_err;
        }
 
        return 0;