From: Nicholas Piggin <npiggin@gmail.com>
Date: Tue, 13 Aug 2024 20:23:21 +0000 (+0100)
Subject: Revert "replay: stop us hanging in rr_wait_io_event"
X-Git-Tag: qemu-xen-4.20.0~15^2~8
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=94962ff00d09674047aed896e87ba09736cd6941;p=qemu-xen.git

Revert "replay: stop us hanging in rr_wait_io_event"

This reverts commit 1f881ea4a444ef36a8b6907b0b82be4b3af253a2.

That commit causes reverse_debugging.py test failures, and does
not seem to solve the root cause of the problem x86-64 still
hangs in record/replay tests.

The problem with short-cutting the iowait that was taken during
record phase is that related events will not get consumed at the
same points (e.g., reading the clock).

A hang with zero icount always seems to be a symptom of an earlier
problem that has caused the recording to become out of synch with
the execution and consumption of events by replay.

Acked-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Message-Id: <20240813050638.446172-6-npiggin@gmail.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20240813202329.1237572-14-alex.bennee@linaro.org>
---

diff --git a/accel/tcg/tcg-accel-ops-rr.c b/accel/tcg/tcg-accel-ops-rr.c
index 48c38714bd..c59c77da4b 100644
--- a/accel/tcg/tcg-accel-ops-rr.c
+++ b/accel/tcg/tcg-accel-ops-rr.c
@@ -109,7 +109,7 @@ static void rr_wait_io_event(void)
 {
     CPUState *cpu;
 
-    while (all_cpu_threads_idle() && replay_can_wait()) {
+    while (all_cpu_threads_idle()) {
         rr_stop_kick_timer();
         qemu_cond_wait_bql(first_cpu->halt_cond);
     }
diff --git a/include/sysemu/replay.h b/include/sysemu/replay.h
index f229b2109c..8102fa54f0 100644
--- a/include/sysemu/replay.h
+++ b/include/sysemu/replay.h
@@ -73,11 +73,6 @@ int replay_get_instructions(void);
 /*! Updates instructions counter in replay mode. */
 void replay_account_executed_instructions(void);
 
-/**
- * replay_can_wait: check if we should pause for wait-io
- */
-bool replay_can_wait(void);
-
 /* Processing clocks and other time sources */
 
 /*! Save the specified clock */
diff --git a/replay/replay.c b/replay/replay.c
index b8564a4813..895fa6b67a 100644
--- a/replay/replay.c
+++ b/replay/replay.c
@@ -451,27 +451,6 @@ void replay_start(void)
     replay_enable_events();
 }
 
-/*
- * For none/record the answer is yes.
- */
-bool replay_can_wait(void)
-{
-    if (replay_mode == REPLAY_MODE_PLAY) {
-        /*
-         * For playback we shouldn't ever be at a point we wait. If
-         * the instruction count has reached zero and we have an
-         * unconsumed event we should go around again and consume it.
-         */
-        if (replay_state.instruction_count == 0 && replay_state.has_unread_data) {
-            return false;
-        } else {
-            replay_sync_error("Playback shouldn't have to iowait");
-        }
-    }
-    return true;
-}
-
-
 void replay_finish(void)
 {
     if (replay_mode == REPLAY_MODE_NONE) {