[PATCH 2/9] rtla/tests: Add get_workload_pids() helper

[Tomas Glozar <tglozar@redhat.com>]

RTLA runtime tests that check workload processes (currently the test
case "verify -P/--priority" of timerlat.t and "verify the --priority/-P
param" of osnoise.t) use "pgrep timerlatu/" or "pgrep osnoise/"
respectively to identify the workload.

Make them more robust by adding a get_workload_pids() helper that
finds the main rtla process and returns the PIDs of all siblings other
than the test script itself, plus all child processes of kthreadd that
have the osnoise/timerlat kthread pattern comm.

This filters out any spurious processes not related to the running test
that happen to have "timerlatu/" or "osnoise/" in their command, for
example, a user grepping the same names at the time of the running of
the test.

Signed-off-by: Tomas Glozar <tglozar@redhat.com>
---
 tools/tracing/rtla/tests/osnoise.t                    |  2 +-
 tools/tracing/rtla/tests/scripts/check-priority.sh    |  8 ++++----
 .../rtla/tests/scripts/lib/get_workload_pids.sh       | 11 +++++++++++
 tools/tracing/rtla/tests/timerlat.t                   |  2 +-
 4 files changed, 17 insertions(+), 6 deletions(-)
 create mode 100644 tools/tracing/rtla/tests/scripts/lib/get_workload_pids.sh

diff --git a/tools/tracing/rtla/tests/osnoise.t b/tools/tracing/rtla/tests/osnoise.t
index ce3a448b1f87..ed6ff0cc3329 100644
--- a/tools/tracing/rtla/tests/osnoise.t
+++ b/tools/tracing/rtla/tests/osnoise.t
@@ -10,7 +10,7 @@ check "verify help page" \
 check_top_hist "verify help page" \
 	"osnoise TOOL --help" 0 "rtla osnoise"
 check_top_q_hist "verify the --priority/-P param" \
-	"osnoise TOOL -P F:1 -c 0 -r 900000 -d 10s -S 1 --on-threshold shell,command=\"tests/scripts/check-priority.sh osnoise/ SCHED_FIFO 1\"" \
+	"osnoise TOOL -P F:1 -c 0 -r 900000 -d 10s -S 1 --on-threshold shell,command=\"tests/scripts/check-priority.sh SCHED_FIFO 1\"" \
 	2 "Priorities are set correctly"
 check_top_q_hist "verify the --stop/-s param" \
 	"osnoise TOOL -s 30 -T 1" 2 "osnoise hit stop tracing"
diff --git a/tools/tracing/rtla/tests/scripts/check-priority.sh b/tools/tracing/rtla/tests/scripts/check-priority.sh
index 79b702a34a96..b51d5232a868 100755
--- a/tools/tracing/rtla/tests/scripts/check-priority.sh
+++ b/tools/tracing/rtla/tests/scripts/check-priority.sh
@@ -1,8 +1,8 @@
 #!/bin/bash
 # SPDX-License-Identifier: GPL-2.0
-pids="$(pgrep ^$1)" || exit 1
-for pid in $pids
+. "$(dirname $0)/lib/get_workload_pids.sh"
+for pid in $(get_workload_pids)
 do
-  chrt -p $pid | cut -d ':' -f 2 | head -n1 | grep "^ $2\$" >/dev/null
-  chrt -p $pid | cut -d ':' -f 2 | tail -n1 | grep "^ $3\$" >/dev/null
+  chrt -p $pid | cut -d ':' -f 2 | head -n1 | grep "^ $1\$" >/dev/null
+  chrt -p $pid | cut -d ':' -f 2 | tail -n1 | grep "^ $2\$" >/dev/null
 done && echo "Priorities are set correctly"
diff --git a/tools/tracing/rtla/tests/scripts/lib/get_workload_pids.sh b/tools/tracing/rtla/tests/scripts/lib/get_workload_pids.sh
new file mode 100644
index 000000000000..8aff98cd2c1f
--- /dev/null
+++ b/tools/tracing/rtla/tests/scripts/lib/get_workload_pids.sh
@@ -0,0 +1,11 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+get_workload_pids() {
+    local shell_pid=$$
+    local rtla_pid=$(ps -o ppid= $shell_pid)
+
+    # kernel threads
+    pgrep -P $(pgrep ^kthreadd$) -f '^(osnoise|timerlat)/[0-9]+$'
+    # user threads
+    pgrep -P $rtla_pid | grep -v "^$shell_pid$"
+}
diff --git a/tools/tracing/rtla/tests/timerlat.t b/tools/tracing/rtla/tests/timerlat.t
index d7944710a859..765dffd9d42a 100644
--- a/tools/tracing/rtla/tests/timerlat.t
+++ b/tools/tracing/rtla/tests/timerlat.t
@@ -27,7 +27,7 @@ check_top_hist "verify help page" \
 check_top_hist "verify -s/--stack" \
 	"timerlat TOOL -s 3 -T 10 -t" 2 "Blocking thread stack trace"
 check_top_hist "verify -P/--priority" \
-	"timerlat TOOL -P F:1 -c 0 -d 10s -T 1 --on-threshold shell,command=\"tests/scripts/check-priority.sh timerlatu/ SCHED_FIFO 1\"" \
+	"timerlat TOOL -P F:1 -c 0 -d 10s -T 1 --on-threshold shell,command=\"tests/scripts/check-priority.sh SCHED_FIFO 1\"" \
 	2 "Priorities are set correctly"
 check_top_hist "test in nanoseconds" \
 	"timerlat TOOL -i 2 -c 0 -n -d 10s" 2 "ns"
-- 
2.53.0