From 4e028f841234553b6dcb6812dad833f060970075 Mon Sep 17 00:00:00 2001
From: Marton Erdos <marton.erdos@arm.com>
Date: Thu, 17 Jun 2021 02:34:09 +0100
Subject: [PATCH] cpu-o3: Fix "OldestReady" scheduling bug

Fixed a bug in the SMT scheduling function oldestReady(), where
the oldest sequence number and its thread id were mixed up.

Change-Id: I31df5eac73ecabbe04fb54624ee1b1867fa4d3c0
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/46940
Reviewed-by: Richard Cooper <richard.cooper@arm.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
---
 src/cpu/o3/commit.cc | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/cpu/o3/commit.cc b/src/cpu/o3/commit.cc
index 2359c1a12d..23265d4e33 100644
--- a/src/cpu/o3/commit.cc
+++ b/src/cpu/o3/commit.cc
@@ -1498,6 +1498,7 @@ ThreadID
 Commit::oldestReady()
 {
     unsigned oldest = 0;
+    unsigned oldest_seq_num = 0;
     bool first = true;
 
     std::list<ThreadID>::iterator threads = activeThreads->begin();
@@ -1517,9 +1518,11 @@ Commit::oldestReady()
 
                 if (first) {
                     oldest = tid;
+                    oldest_seq_num = head_inst->seqNum;
                     first = false;
-                } else if (head_inst->seqNum < oldest) {
+                } else if (head_inst->seqNum < oldest_seq_num) {
                     oldest = tid;
+                    oldest_seq_num = head_inst->seqNum;
                 }
             }
         }