[PATCH 09/11] tests: start stalld before starvation_gen in all tests

[Wander Lairson Costa <wander@redhat.com>]

The test sections previously started starvation_gen before stalld,
based on a belief that stalld's idle detection could miss tasks
appearing after it began scanning.  Source analysis showed this
concern was unfounded -- stalld re-scans continuously and will detect
starvation regardless of when the starved tasks appear.  Meanwhile,
the old ordering introduced intermittent failures: starvation_gen
could finish and exit before stalld had a chance to scan, causing
timeouts in assert_starvation_detected and wait_for_boost_detected.

Reorder all 15 test sections across test_fifo_boosting.sh,
test_fifo_priority_starvation.sh, test_starvation_detection.sh,
test_starvation_threshold.sh, and test_log_only.sh so that
start_stalld_with_log runs before start_starvation_gen.  Remove stale
comments about the old ordering rationale ("Create starvation FIRST",
"avoid idle detection race").

Signed-off-by: Wander Lairson Costa <wander@redhat.com>
---
 tests/functional/test_fifo_boosting.sh        | 22 +++++------
 .../test_fifo_priority_starvation.sh          | 38 ++++++++-----------
 tests/functional/test_log_only.sh             | 10 ++---
 tests/functional/test_starvation_detection.sh | 18 ++++-----
 tests/functional/test_starvation_threshold.sh | 23 +++++------
 5 files changed, 45 insertions(+), 66 deletions(-)

diff --git a/tests/functional/test_fifo_boosting.sh b/tests/functional/test_fifo_boosting.sh
index e489950..4d2841d 100755
--- a/tests/functional/test_fifo_boosting.sh
+++ b/tests/functional/test_fifo_boosting.sh
@@ -22,16 +22,14 @@ init_functional_test "SCHED_FIFO Boosting Mechanism" "test_fifo_boost"
 test_section "Test 1: FIFO Boost with -F Flag"
 
 threshold=5
-# Create starvation FIRST (before stalld starts)
 starvation_duration=$((threshold + 5))
-log "Creating starvation on CPU ${TEST_CPU} for ${starvation_duration}s"
-start_starvation_gen -c ${TEST_CPU} -p 80 -n 2 -d ${starvation_duration}
 
 log "Starting stalld with -F flag to force SCHED_FIFO boosting"
-# Note: -F requires non-single-threaded mode (aggressive mode)
-# Use -g 1 for 1-second granularity to ensure timely detection
 start_stalld_with_log "${STALLD_LOG}" -f -v -g 1 -N -F -A -t $threshold -c ${TEST_CPU} -a ${STALLD_CPU}
 
+log "Creating starvation on CPU ${TEST_CPU} for ${starvation_duration}s"
+start_starvation_gen -c ${TEST_CPU} -p 80 -n 2 -d ${starvation_duration}
+
 # Wait for boosting
 log "Waiting for boost detection..."
 assert_boost_detected "${STALLD_LOG}" "Boosting occurred with -F flag"
@@ -48,14 +46,13 @@ test_section "Test 2: FIFO Priority Verification"
 threshold=5
 rm -f "${STALLD_LOG}"
 
-# Create starvation FIRST
+log "Starting stalld with -F flag (FIFO boosting)"
+start_stalld_with_log "${STALLD_LOG}" -f -v -g 1 -N -F -A -t $threshold -c ${TEST_CPU} -a ${STALLD_CPU}
+
 log "Creating starvation on CPU ${TEST_CPU}"
 start_starvation_gen -c ${TEST_CPU} -p 80 -n 1 -d 10
 tracked_pid=$(find_starved_child "${STARVE_PID}")
 
-log "Starting stalld with -F flag (FIFO boosting)"
-start_stalld_with_log "${STALLD_LOG}" -f -v -g 1 -N -F -A -t $threshold -c ${TEST_CPU} -a ${STALLD_CPU}
-
 # Wait for boosting
 log "Waiting for boost detection..."
 wait_for_boost_detected "${STALLD_LOG}"
@@ -101,13 +98,12 @@ log "  Expected cycles: ~5"
 
 rm -f "${STALLD_LOG}"
 
-# Create starvation FIRST
-log "Creating starvation on CPU ${TEST_CPU}"
-start_starvation_gen -c ${TEST_CPU} -p 80 -n 1 -d 12
-
 start_stalld_with_log "${STALLD_LOG}" -f -v -g 1 -N -F -A -t $threshold -c ${TEST_CPU} -a ${STALLD_CPU} \
     -d ${boost_duration} -p ${boost_period} -r ${boost_runtime}
 
+log "Creating starvation on CPU ${TEST_CPU}"
+start_starvation_gen -c ${TEST_CPU} -p 80 -n 1 -d 12
+
 # Wait for boosting to start
 log "Waiting for boost detection..."
 wait_for_boost_detected "${STALLD_LOG}"
diff --git a/tests/functional/test_fifo_priority_starvation.sh b/tests/functional/test_fifo_priority_starvation.sh
index 028b825..86c6517 100755
--- a/tests/functional/test_fifo_priority_starvation.sh
+++ b/tests/functional/test_fifo_priority_starvation.sh
@@ -27,17 +27,16 @@ test_section "Test 1: Basic FIFO-on-FIFO Starvation Detection"
 log "Testing: FIFO:10 blocker starves FIFO:5 blockee"
 
 threshold=5
-
-# Create starvation BEFORE starting stalld to avoid idle detection race
 starvation_duration=$((threshold + 5))
+
+log "Starting stalld with ${threshold}s threshold (log-only mode)"
+start_stalld_with_log "${STALLD_LOG}" -f -v -l -t $threshold -c ${TEST_CPU} -a ${STALLD_CPU}
+
 log "Creating FIFO-on-FIFO starvation on CPU ${TEST_CPU} for ${starvation_duration}s"
 log "  Blocker: SCHED_FIFO priority 10"
 log "  Blockee: SCHED_FIFO priority 5"
 start_starvation_gen -c ${TEST_CPU} -p 10 -b 5 -n 2 -d ${starvation_duration}
 
-log "Starting stalld with ${threshold}s threshold (log-only mode)"
-start_stalld_with_log "${STALLD_LOG}" -f -v -l -t $threshold -c ${TEST_CPU} -a ${STALLD_CPU}
-
 # Wait for starvation detection
 log "Waiting for starvation detection..."
 assert_starvation_detected "${STALLD_LOG}" "FIFO-on-FIFO starvation detected"
@@ -57,6 +56,9 @@ rm -f "${STALLD_LOG}"
 threshold=5
 boost_duration=3
 
+log "Starting stalld with boosting enabled"
+start_stalld_with_log "${STALLD_LOG}" -f -v -N -t $threshold -c ${TEST_CPU} -a ${STALLD_CPU} -d ${boost_duration}
+
 log "Creating FIFO-on-FIFO starvation on CPU ${TEST_CPU}"
 start_starvation_gen -c ${TEST_CPU} -p 10 -b 5 -n 1 -d 12
 
@@ -69,9 +71,6 @@ if [ -n "${blockee_pid}" ]; then
     log "Blockee task PID ${blockee_pid}, context switches before boost: ${ctxt_before}"
 fi
 
-log "Starting stalld with boosting enabled"
-start_stalld_with_log "${STALLD_LOG}" -f -v -N -t $threshold -c ${TEST_CPU} -a ${STALLD_CPU} -d ${boost_duration}
-
 # Wait for detection and boosting
 wait_for_boost_detected "${STALLD_LOG}"
 sleep ${boost_duration}
@@ -103,16 +102,15 @@ log "Verify duration accumulates correctly (task merging)"
 
 rm -f "${STALLD_LOG}"
 threshold=3
-
-# Create long starvation to trigger multiple detection cycles
 starvation_duration=12
-log "Creating long FIFO-on-FIFO starvation for ${starvation_duration}s"
-start_starvation_gen -c ${TEST_CPU} -p 10 -b 5 -n 2 -d ${starvation_duration}
 
 log "Starting stalld with ${threshold}s threshold (log-only mode)"
 log "Will monitor for multiple detection cycles to verify timestamp preservation"
 start_stalld_with_log "${STALLD_LOG}" -f -v -l -t $threshold -c ${TEST_CPU} -a ${STALLD_CPU}
 
+log "Creating long FIFO-on-FIFO starvation for ${starvation_duration}s"
+start_starvation_gen -c ${TEST_CPU} -p 10 -b 5 -n 2 -d ${starvation_duration}
+
 # Wait for multiple detection cycles
 log "Waiting for first detection cycle..."
 wait_for_starvation_detected "${STALLD_LOG}"
@@ -147,15 +145,14 @@ log "Testing edge case with only 1 priority difference"
 rm -f "${STALLD_LOG}"
 threshold=5
 
-# Test with very close priorities
+log "Starting stalld with ${threshold}s threshold"
+start_stalld_with_log "${STALLD_LOG}" -f -v -l -t $threshold -c ${TEST_CPU} -a ${STALLD_CPU}
+
 log "Creating FIFO-on-FIFO starvation with close priorities"
 log "  Blocker: SCHED_FIFO priority 6"
 log "  Blockee: SCHED_FIFO priority 5"
 start_starvation_gen -c ${TEST_CPU} -p 6 -b 5 -n 1 -d $((threshold + 5))
 
-log "Starting stalld with ${threshold}s threshold"
-start_stalld_with_log "${STALLD_LOG}" -f -v -l -t $threshold -c ${TEST_CPU} -a ${STALLD_CPU}
-
 # Wait for starvation detection
 log "Waiting for starvation detection..."
 if wait_for_starvation_detected "${STALLD_LOG}"; then
@@ -180,16 +177,13 @@ log "Ensure stalld boosts the blockee (FIFO:5), not the blocker (FIFO:10)"
 rm -f "${STALLD_LOG}"
 threshold=5
 
+log "Starting stalld with boosting enabled"
+start_stalld_with_log "${STALLD_LOG}" -f -v -N -t $threshold -c ${TEST_CPU} -a ${STALLD_CPU}
+
 log "Creating FIFO-on-FIFO starvation"
 start_starvation_gen -c ${TEST_CPU} -p 10 -b 5 -n 2 -d 12 -v
-
-# Extract blocker and blockee PIDs from starvation_gen output
-# The output shows "Blocker TID: <pid>" and "Blockee N TID: <pid>"
 log "Starvation generator PID: ${STARVE_PID}"
 
-log "Starting stalld with boosting enabled"
-start_stalld_with_log "${STALLD_LOG}" -f -v -N -t $threshold -c ${TEST_CPU} -a ${STALLD_CPU}
-
 # Wait for boosting
 log "Waiting for boost detection..."
 if wait_for_boost_detected "${STALLD_LOG}"; then
diff --git a/tests/functional/test_log_only.sh b/tests/functional/test_log_only.sh
index b38db70..cba7596 100755
--- a/tests/functional/test_log_only.sh
+++ b/tests/functional/test_log_only.sh
@@ -44,16 +44,12 @@ echo "Stalld will run on CPU ${STALLD_CPU}"
 LOG_FILE="/tmp/stalld_test_log_only_$$.log"
 CLEANUP_FILES+=("${LOG_FILE}")
 
-echo "Creating starvation on CPU ${TEST_CPU} (will run for 10 seconds)"
-
-# Start starvation generator BEFORE stalld to ensure CPU is busy from the start
-start_starvation_gen -c ${TEST_CPU} -p 10 -n 1 -d 10
-STARVGEN_PID=${STARVE_PID}
-
-# Start stalld in log-only mode with verbose output to capture logs
 echo "Starting stalld in log-only mode with 5 second threshold"
 start_stalld_with_log "${LOG_FILE}" -f -v -l -t 5 -c ${TEST_CPU} -a ${STALLD_CPU}
 
+echo "Creating starvation on CPU ${TEST_CPU} (will run for 10 seconds)"
+start_starvation_gen -c ${TEST_CPU} -p 10 -n 1 -d 10
+STARVGEN_PID=${STARVE_PID}
 echo "Starvation generator started (PID ${STARVGEN_PID})"
 echo "Waiting for starvation detection..."
 
diff --git a/tests/functional/test_starvation_detection.sh b/tests/functional/test_starvation_detection.sh
index 52031c5..9702f99 100755
--- a/tests/functional/test_starvation_detection.sh
+++ b/tests/functional/test_starvation_detection.sh
@@ -24,15 +24,14 @@ NUM_CPUS=$(get_num_cpus)
 test_section "Test 1: Basic Starvation Detection"
 
 threshold=5
-
-# Create starvation BEFORE starting stalld to avoid idle detection race
 starvation_duration=$((threshold + 5))
-log "Creating starvation on CPU ${TEST_CPU} for ${starvation_duration}s"
-start_starvation_gen -c ${TEST_CPU} -p 80 -n 2 -d ${starvation_duration}
 
 log "Starting stalld with ${threshold}s threshold (log-only mode)"
 start_stalld_with_log "${STALLD_LOG}" -f -v -N -l -t $threshold -c ${TEST_CPU} -a ${STALLD_CPU}
 
+log "Creating starvation on CPU ${TEST_CPU} for ${starvation_duration}s"
+start_starvation_gen -c ${TEST_CPU} -p 80 -n 2 -d ${starvation_duration}
+
 # Wait for starvation detection
 log "Waiting for starvation detection..."
 assert_starvation_detected "${STALLD_LOG}" "Starvation detected"
@@ -50,13 +49,12 @@ test_section "Test 2: Context Switch Count Tracking"
 rm -f "${STALLD_LOG}"
 threshold=5
 
-# Create starvation
-log "Creating starvation on CPU ${TEST_CPU}"
-start_starvation_gen -c ${TEST_CPU} -p 80 -n 1 -d 10
-
 log "Starting stalld with ${threshold}s threshold (log-only mode)"
 start_stalld_with_log "${STALLD_LOG}" -f -v -N -l -t $threshold -c ${TEST_CPU} -a ${STALLD_CPU}
 
+log "Creating starvation on CPU ${TEST_CPU}"
+start_starvation_gen -c ${TEST_CPU} -p 80 -n 1 -d 10
+
 # Wait for starvation detection
 log "Waiting for starvation detection..."
 wait_for_starvation_detected "${STALLD_LOG}"
@@ -116,6 +114,8 @@ else
     rm -f "${STALLD_LOG}"
     threshold=5
 
+    start_stalld_with_log "${STALLD_LOG}" -f -v -N -l -t $threshold -c ${CPU0},${CPU1} -a ${STALLD_CPU_MULTI}
+
     # Create starvation on CPU0
     log "Creating starvation on CPU ${CPU0}"
     start_starvation_gen -c ${CPU0} -p 80 -n 1 -d 12
@@ -126,8 +126,6 @@ else
     start_starvation_gen -c ${CPU1} -p 80 -n 1 -d 12
     STARVE_PID1=${STARVE_PID}
 
-    start_stalld_with_log "${STALLD_LOG}" -f -v -N -l -t $threshold -c ${CPU0},${CPU1} -a ${STALLD_CPU_MULTI}
-
     # Wait for starvation detection on both CPUs
     log "Waiting for starvation detection on CPU ${CPU0}..."
     assert_starvation_detected "${STALLD_LOG}" "Starvation detected on CPU ${CPU0}" "30" "${CPU0}"
diff --git a/tests/functional/test_starvation_threshold.sh b/tests/functional/test_starvation_threshold.sh
index b372a87..bb4a862 100755
--- a/tests/functional/test_starvation_threshold.sh
+++ b/tests/functional/test_starvation_threshold.sh
@@ -25,16 +25,14 @@ init_functional_test "Starvation Threshold Option (-t)" "test_threshold"
 test_section "Test 1: Custom threshold of 5 seconds"
 
 threshold=5
-
-# Create starvation BEFORE starting stalld (avoid detecting kworker tasks)
 starvation_duration=10
-log "Creating starvation on CPU ${TEST_CPU} for ${starvation_duration}s"
-start_starvation_gen -c "${TEST_CPU}" -p 80 -n 2 -d ${starvation_duration}
 
 log "Starting stalld with ${threshold}s threshold"
-# Use -i to ignore kernel workers that may starve before our test tasks
 start_stalld_with_log "${STALLD_LOG}" -f -v -N -M -g 1 -i "ksoftirqd,kworker" -c "${TEST_CPU}" -a "${STALLD_CPU}" -t ${threshold}
 
+log "Creating starvation on CPU ${TEST_CPU} for ${starvation_duration}s"
+start_starvation_gen -c "${TEST_CPU}" -p 80 -n 2 -d ${starvation_duration}
+
 # Wait for starvation detection
 log "Waiting for detection (threshold: ${threshold}s)"
 
@@ -51,15 +49,14 @@ test_section "Test 2: No detection before threshold"
 threshold=10
 rm -f "${STALLD_LOG}"
 
-# Create starvation BEFORE starting stalld (avoid detecting kworker tasks)
-# Create starvation that will last 6 seconds (less than threshold)
 starvation_duration=6
-log "Creating short starvation (${starvation_duration}s) with threshold of ${threshold}s"
-start_starvation_gen -c "${TEST_CPU}" -p 80 -n 2 -d ${starvation_duration}
 
 log "Starting stalld with ${threshold}s threshold"
 start_stalld_with_log "${STALLD_LOG}" -f -v -N -M -g 1 -c "${TEST_CPU}" -a "${STALLD_CPU}" -t ${threshold}
 
+log "Creating short starvation (${starvation_duration}s) with threshold of ${threshold}s"
+start_starvation_gen -c "${TEST_CPU}" -p 80 -n 2 -d ${starvation_duration}
+
 # Wait for starvation generator to fully complete
 wait "${STARVE_PID}" 2>/dev/null || true
 
@@ -82,16 +79,14 @@ test_section "Test 3: Shorter threshold (3 seconds)"
 threshold=3
 rm -f "${STALLD_LOG}"
 
-# Create starvation BEFORE starting stalld (avoid detecting kworker tasks)
-# Create starvation for 8 seconds
 starvation_duration=8
-log "Creating starvation for ${starvation_duration}s with threshold of ${threshold}s"
-start_starvation_gen -c "${TEST_CPU}" -p 80 -n 2 -d ${starvation_duration}
 
 log "Starting stalld with ${threshold}s threshold"
-# Use -i to ignore kernel workers that may starve before our test tasks
 start_stalld_with_log "${STALLD_LOG}" -f -v -N -M -g 1 -i "ksoftirqd,kworker" -c "${TEST_CPU}" -a "${STALLD_CPU}" -t ${threshold}
 
+log "Creating starvation for ${starvation_duration}s with threshold of ${threshold}s"
+start_starvation_gen -c "${TEST_CPU}" -p 80 -n 2 -d ${starvation_duration}
+
 # Wait for starvation detection
 log "Waiting for detection (threshold: ${threshold}s)"
 
-- 
2.55.0