[PATCH 07/12] stalld.c: Add starvation logging in single-threaded log-only mode

[Clark Williams <clrkwllms@kernel.org>]

From: Clark Williams <williams@redhat.com>

In single-threaded mode with -l/--log_only flag, stalld was not logging
the "starved" message when tasks reached the starvation threshold. This
was because the config_log_only check occurred before any logging, and
the "starved" message (present in check_starving_tasks() for per-CPU
threading modes) was missing from boost_cpu_starving_vector().

This caused test_log_only.sh to fail when looking for the "starved"
message in the log output.

Changes to boost_cpu_starving_vector():
- Move config_log_only check after starvation detection
- Add log_msg() call to output "starved" message when threshold reached
- Reset timestamp (cpu->since) in log-only mode to prevent continuous
  logging of the same starvation event
- Change threshold comparison from <= to < for consistency with
  check_starving_tasks()

This ensures consistent logging behavior between single-threaded mode
and per-CPU threading modes when using log-only mode.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
Signed-off-by: Clark Williams <clrkwllms@kernel.org>
Signed-off-by: Clark Williams <williams@redhat.com>
---
 src/stalld.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/stalld.c b/src/stalld.c
index 6adc3e9a8cea..ebca23105ce9 100644
--- a/src/stalld.c
+++ b/src/stalld.c
@@ -924,12 +924,22 @@ int boost_cpu_starving_vector(struct cpu_starving_task_info *vector, int nr_cpus
 			log_verbose("\t cpu %d: pid: %d starving for %llu\n",
 				    i, cpu->pid, (now - cpu->since));
 
-		if (config_log_only)
+		/* Skip if no task or not starving long enough */
+		if (cpu->pid == 0 || (now - cpu->since) < config_starving_threshold)
 			continue;
 
-		/* Skip if no task or not starving long enough */
-		if (cpu->pid == 0 || (now - cpu->since) <= config_starving_threshold)
+		/* Log when task has reached starvation threshold */
+		if ((now - cpu->since) >= config_starving_threshold) {
+			log_msg("%s-%d starved on CPU %d for %d seconds\n",
+				cpu->task.comm, cpu->pid, i,
+				(now - cpu->since));
+		}
+
+		if (config_log_only) {
+			/* Reset timestamp to avoid continuous logging */
+			cpu->since = now;
 			continue;
+		}
 
 		/* Skip if task is on denylist */
 		if (config_ignore && !check_task_ignore(&cpu->task))
-- 
2.51.0