lib: Figure out if we are being starved for cpu

If a thread timer should have popped CPU_CONSUMED_CHECK
seconds in the past, and we are only handling it now.  Consider
the thread starved and notice it.

Signed-off-by: Donald Sharp <sharpd@nvidia.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/lib/thread.c b/lib/thread.c
index 77e34f48f..73e0e4887 100644
--- a/lib/thread.c
+++ b/lib/thread.c
@@ -1651,12 +1651,31 @@ static void thread_process_io(struct thread_master *m, unsigned int num)
 static unsigned int thread_process_timers(struct thread_master *m,
 					  struct timeval *timenow)
 {
+	struct timeval prev = *timenow;
+	bool displayed = false;
 	struct thread *thread;
 	unsigned int ready = 0;
 
 	while ((thread = thread_timer_list_first(&m->timer))) {
 		if (timercmp(timenow, &thread->u.sands, <))
 			break;
+		prev = thread->u.sands;
+		prev.tv_sec += 4;
+		/*
+		 * If the timer would have popped 4 seconds in the
+		 * past then we are in a situation where we are
+		 * really getting behind on handling of events.
+		 * Let's log it and do the right thing with it.
+		 */
+		if (timercmp(timenow, &prev, >)) {
+			if (!displayed)
+				flog_warn(
+					EC_LIB_STARVE_THREAD,
+					"Thread Starvation: %pTHD was scheduled to pop greater than 4s ago",
+					thread);
+			displayed = true;
+		}
+
 		thread_timer_list_pop(&m->timer);
 		thread->type = THREAD_READY;
 		thread_list_add_tail(&m->ready, thread);