From 6ead4469ddd58969dddfd9450e79851772f312a3 Mon Sep 17 00:00:00 2001
From: Donald Sharp <sharpd@nvidia.com>
Date: Thu, 2 Nov 2023 16:46:27 -0400
Subject: [PATCH] MORE WORK

---
 lib/event.c    | 15 ++++++++++++---
 lib/frrevent.h |  2 ++
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/lib/event.c b/lib/event.c
index 93df0383b882..282f0252a960 100644
--- a/lib/event.c
+++ b/lib/event.c
@@ -1654,6 +1654,10 @@ static inline void thread_process_io_inner_loop(struct event_loop *m, unsigned i
  * Walks through file descriptor array looking for those pollfds whose .revents
  * field has something interesting. Deletes any invalid file descriptors.
  *
+ * Try to impart some impartiality to handling of reads.  The event
+ * system will cycle through the fd's available for being read
+ * giving each one a chance to go first.
+ *
  * @param m the thread master
  * @param num the number of active file descriptors (return value of poll())
  */
@@ -1661,10 +1665,15 @@ static void thread_process_io(struct event_loop *m, unsigned int num)
 {
 	unsigned int ready = 0;
 	struct pollfd *pfds = m->handler.copy;
+	nfds_t last_read = m->last_read & m->handler.copycount;
 
-	for (nfds_t i = 0; i < m->handler.copycount && ready < num; ++i) {
-	  thread_process_io_inner_loop(m, num, pfds, &i, &ready);
-	}
+	for (nfds_t i = last_read; i < m->handler.copycount && ready < num; ++i)
+		thread_process_io_inner_loop(m, num, pfds, &i, &ready);
+
+	for (nfds_t i = 0; i < last_read && ready < num; ++i)
+		thread_process_io_inner_loop(m, num, pfds, &i, &ready);
+
+	m->last_read++;
 }
 
 /* Add all timers that have popped to the ready list. */
diff --git a/lib/frrevent.h b/lib/frrevent.h
index 3f74df359bc2..616fe131af5c 100644
--- a/lib/frrevent.h
+++ b/lib/frrevent.h
@@ -91,6 +91,8 @@ struct event_loop {
 	pthread_mutex_t mtx;
 	pthread_t owner;
 
+	nfds_t last_read;
+
 	bool ready_run_loop;
 	RUSAGE_T last_getrusage;
 };