[Qemu-devel] [PATCH v3 12/12] replay: assert time only goes forward

[Alex Bennée]

If we find ourselves trying to add an event to the log where time has
gone backwards it is because a vCPU event has occurred and the
main-loop is not yet aware of time moving forward. This should not
happen and if it does its better to fail early than generate a log
that will have weird behaviour.

Signed-off-by: Alex Bennée <alex.ben...@linaro.org>
---
 replay/replay-internal.c | 4 ++++
 replay/replay.c          | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/replay/replay-internal.c b/replay/replay-internal.c
index bea7b4aa6b..fca8514012 100644
--- a/replay/replay-internal.c
+++ b/replay/replay-internal.c
@@ -195,6 +195,10 @@ void replay_save_instructions(void)
     if (replay_file && replay_mode == REPLAY_MODE_RECORD) {
         replay_mutex_lock();
         int diff = (int)(replay_get_current_step() - 
replay_state.current_step);
+
+        /* Time can only go forward */
+        assert(diff >= 0);
+
         if (diff > 0) {
             replay_put_event(EVENT_INSTRUCTION);
             replay_put_dword(diff);
diff --git a/replay/replay.c b/replay/replay.c
index 9e0724e756..f810628cac 100644
--- a/replay/replay.c
+++ b/replay/replay.c
@@ -84,6 +84,10 @@ void replay_account_executed_instructions(void)
         if (replay_state.instructions_count > 0) {
             int count = (int)(replay_get_current_step()
                               - replay_state.current_step);
+
+            /* Time can only go forward */
+            assert(count >= 0);
+
             replay_state.instructions_count -= count;
             replay_state.current_step += count;
             if (replay_state.instructions_count == 0) {
-- 
2.11.0