[PATCH 6.6 3/4] rtla/timerlat_hist: Set OSNOISE_WORKLOAD for kernel threads

[Tomas Glozar <tglozar@redhat.com>]

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>
---
 tools/tracing/rtla/src/timerlat_hist.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/tools/tracing/rtla/src/timerlat_hist.c b/tools/tracing/rtla/src/timerlat_hist.c
index ab13a9392bff..198cdf75c837 100644
--- 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;
-- 
2.48.1