[PATCH stalld 11/52] tests: Fix repeated log match finding same line

Test 3 in the FIFO priority starvation suite calls
wait_for_starvation_detected three times on the same log file to
wait for three detection cycles. However, the underlying
wait_for_log_message helper uses tail -f -n +1 which reads from
the beginning of the file on every invocation, so all three calls
instantly match the same first line.

Introduce a wait_for_n_log_matches helper that polls grep -c until
the match count reaches the requested threshold, and use it to
replace the repeated calls.

Signed-off-by: Wander Lairson Costa <[email protected]>

Assisted-by: Claude Code:claude-opus-4-6[1m] [PAL]
Signed-off-by: Wander Lairson Costa <[email protected]>
---
 .../test_fifo_priority_starvation.sh          | 10 +++------
 tests/helpers/test_helpers.sh                 | 21 ++++++++++++++++++-
 2 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/tests/functional/test_fifo_priority_starvation.sh b/tests/functional/test_fifo_priority_starvation.sh
index 172bc9a..8f78a75 100755
--- a/tests/functional/test_fifo_priority_starvation.sh
+++ b/tests/functional/test_fifo_priority_starvation.sh
@@ -139,13 +139,9 @@ start_stalld_with_log "${STALLD_LOG}" -f -v -l -t $threshold -c ${TEST_CPU} -a $
 # Wait for multiple detection cycles
 log "Waiting for first detection cycle..."
 wait_for_starvation_detected "${STALLD_LOG}"
-log "First detection cycle should have occurred"
-log "Waiting for second detection cycle..."
-wait_for_starvation_detected "${STALLD_LOG}"
-log "Second detection cycle should have occurred"
-log "Waiting for third detection cycle..."
-wait_for_starvation_detected "${STALLD_LOG}"
-log "Third detection cycle should have occurred"
+log "First detection cycle occurred, waiting for additional cycles..."
+wait_for_n_log_matches "starved on CPU" 3 "${STALLD_LOG}"
+log "Multiple detection cycles should have occurred"
 
 # Check if we see accumulating starvation time in logs
 # Task merging means the timestamp is preserved, so duration increases
diff --git a/tests/helpers/test_helpers.sh b/tests/helpers/test_helpers.sh
index 742b15e..757e5e0 100755
--- a/tests/helpers/test_helpers.sh
+++ b/tests/helpers/test_helpers.sh
@@ -668,6 +668,25 @@ wait_for_boost_detected() {
 	wait_for_log_message "boosted pid" "${timeout}" "${log_file}"
 }
 
+# Wait until a log file contains at least N matches of a pattern.
+#
+# Usage: wait_for_n_log_matches <pattern> <count> <log_file> [timeout]
+wait_for_n_log_matches() {
+	local pattern=$1
+	local count=$2
+	local log_file=$3
+	local timeout=${4:-30}
+	local end=$((SECONDS + timeout))
+
+	while [ $SECONDS -lt $end ]; do
+		local matches
+		matches=$(grep -c "${pattern}" "${log_file}" 2>/dev/null || true)
+		[ "${matches:-0}" -ge "${count}" ] && return 0
+		sleep 1
+	done
+	return 1
+}
+
 # Get thread scheduling policy
 get_thread_policy() {
 	local pid=$1
@@ -1250,7 +1269,7 @@ export -f pass fail assert_equals assert_contains assert_not_contains
 export -f assert_file_exists assert_file_not_exists
 export -f assert_process_running assert_process_not_running
 export -f start_stalld stop_stalld kill_existing_stalld cleanup
-export -f wait_for_log_message wait_for_stalld_ready wait_for_starvation_detected wait_for_boost_detected
+export -f wait_for_log_message wait_for_stalld_ready wait_for_starvation_detected wait_for_boost_detected wait_for_n_log_matches
 export -f get_thread_policy get_thread_priority
 export -f create_cpu_load
 export -f detect_default_backend is_backend_available get_available_backends start_stalld_with_backend
-- 
2.54.0