rtla/timerlat_top: 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 top -u
^\Quit (core dumped)
$ rtla timerlat top -k -d 1s
                                     Timer Latency
  0 00:00:01   |          IRQ Timer Latency (us)        |         Thread Timer Latency (us)
CPU COUNT      |      cur       min       avg       max |      cur       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/20250107144823.239782-4-tglozar@redhat.com
Fixes: cdca4f4e5e8e ("rtla/timerlat_top: 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_top.c b/tools/tracing/rtla/src/timerlat_top.c
index d358cd39f3604ef83aa5a315dc1f00543c84693b..f387597d3ac22502e8bba18567aac168ebfb6467 100644 (file)
--- a/tools/tracing/rtla/src/timerlat_top.c
+++ b/tools/tracing/rtla/src/timerlat_top.c
@@ -851,12 +851,15 @@ timerlat_top_apply_config(struct osnoise_tool *top, struct timerlat_top_params *
                }
        }
 
-       if (params->user_top) {
-               retval = osnoise_set_workload(top->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(top->context, params->kernel_workload);
+       if (retval < -1) {
+               err_msg("Failed to set OSNOISE_WORKLOAD option\n");
+               goto out_err;
        }
 
        if (isatty(STDOUT_FILENO) && !params->quiet)