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Diffstat (limited to 'replay')
-rw-r--r--replay/replay-audio.c14
-rwxr-xr-xreplay/replay-char.c21
-rw-r--r--replay/replay-events.c75
-rw-r--r--replay/replay-internal.c43
-rw-r--r--replay/replay-internal.h17
-rw-r--r--replay/replay-snapshot.c12
-rw-r--r--replay/replay-time.c10
-rw-r--r--replay/replay.c58
8 files changed, 144 insertions, 106 deletions
diff --git a/replay/replay-audio.c b/replay/replay-audio.c
index 3d837434d4..b113836de4 100644
--- a/replay/replay-audio.c
+++ b/replay/replay-audio.c
@@ -19,20 +19,17 @@
 void replay_audio_out(int *played)
 {
     if (replay_mode == REPLAY_MODE_RECORD) {
+        g_assert(replay_mutex_locked());
         replay_save_instructions();
-        replay_mutex_lock();
         replay_put_event(EVENT_AUDIO_OUT);
         replay_put_dword(*played);
-        replay_mutex_unlock();
     } else if (replay_mode == REPLAY_MODE_PLAY) {
+        g_assert(replay_mutex_locked());
         replay_account_executed_instructions();
-        replay_mutex_lock();
         if (replay_next_event_is(EVENT_AUDIO_OUT)) {
             *played = replay_get_dword();
             replay_finish_event();
-            replay_mutex_unlock();
         } else {
-            replay_mutex_unlock();
             error_report("Missing audio out event in the replay log");
             abort();
         }
@@ -44,8 +41,8 @@ void replay_audio_in(int *recorded, void *samples, int *wpos, int size)
     int pos;
     uint64_t left, right;
     if (replay_mode == REPLAY_MODE_RECORD) {
+        g_assert(replay_mutex_locked());
         replay_save_instructions();
-        replay_mutex_lock();
         replay_put_event(EVENT_AUDIO_IN);
         replay_put_dword(*recorded);
         replay_put_dword(*wpos);
@@ -55,10 +52,9 @@ void replay_audio_in(int *recorded, void *samples, int *wpos, int size)
             replay_put_qword(left);
             replay_put_qword(right);
         }
-        replay_mutex_unlock();
     } else if (replay_mode == REPLAY_MODE_PLAY) {
+        g_assert(replay_mutex_locked());
         replay_account_executed_instructions();
-        replay_mutex_lock();
         if (replay_next_event_is(EVENT_AUDIO_IN)) {
             *recorded = replay_get_dword();
             *wpos = replay_get_dword();
@@ -69,9 +65,7 @@ void replay_audio_in(int *recorded, void *samples, int *wpos, int size)
                 audio_sample_from_uint64(samples, pos, left, right);
             }
             replay_finish_event();
-            replay_mutex_unlock();
         } else {
-            replay_mutex_unlock();
             error_report("Missing audio in event in the replay log");
             abort();
         }
diff --git a/replay/replay-char.c b/replay/replay-char.c
index cbf7c04a9f..736cc8c2e6 100755
--- a/replay/replay-char.c
+++ b/replay/replay-char.c
@@ -96,25 +96,24 @@ void *replay_event_char_read_load(void)
 
 void replay_char_write_event_save(int res, int offset)
 {
+    g_assert(replay_mutex_locked());
+
     replay_save_instructions();
-    replay_mutex_lock();
     replay_put_event(EVENT_CHAR_WRITE);
     replay_put_dword(res);
     replay_put_dword(offset);
-    replay_mutex_unlock();
 }
 
 void replay_char_write_event_load(int *res, int *offset)
 {
+    g_assert(replay_mutex_locked());
+
     replay_account_executed_instructions();
-    replay_mutex_lock();
     if (replay_next_event_is(EVENT_CHAR_WRITE)) {
         *res = replay_get_dword();
         *offset = replay_get_dword();
         replay_finish_event();
-        replay_mutex_unlock();
     } else {
-        replay_mutex_unlock();
         error_report("Missing character write event in the replay log");
         exit(1);
     }
@@ -122,23 +121,21 @@ void replay_char_write_event_load(int *res, int *offset)
 
 int replay_char_read_all_load(uint8_t *buf)
 {
-    replay_mutex_lock();
+    g_assert(replay_mutex_locked());
+
     if (replay_next_event_is(EVENT_CHAR_READ_ALL)) {
         size_t size;
         int res;
         replay_get_array(buf, &size);
         replay_finish_event();
-        replay_mutex_unlock();
         res = (int)size;
         assert(res >= 0);
         return res;
     } else if (replay_next_event_is(EVENT_CHAR_READ_ALL_ERROR)) {
         int res = replay_get_dword();
         replay_finish_event();
-        replay_mutex_unlock();
         return res;
     } else {
-        replay_mutex_unlock();
         error_report("Missing character read all event in the replay log");
         exit(1);
     }
@@ -146,19 +143,17 @@ int replay_char_read_all_load(uint8_t *buf)
 
 void replay_char_read_all_save_error(int res)
 {
+    g_assert(replay_mutex_locked());
     assert(res < 0);
     replay_save_instructions();
-    replay_mutex_lock();
     replay_put_event(EVENT_CHAR_READ_ALL_ERROR);
     replay_put_dword(res);
-    replay_mutex_unlock();
 }
 
 void replay_char_read_all_save_buf(uint8_t *buf, int offset)
 {
+    g_assert(replay_mutex_locked());
     replay_save_instructions();
-    replay_mutex_lock();
     replay_put_event(EVENT_CHAR_READ_ALL);
     replay_put_array(buf, offset);
-    replay_mutex_unlock();
 }
diff --git a/replay/replay-events.c b/replay/replay-events.c
index 94a6dcccfc..707de3867b 100644
--- a/replay/replay-events.c
+++ b/replay/replay-events.c
@@ -27,10 +27,6 @@ typedef struct Event {
 } Event;
 
 static QTAILQ_HEAD(, Event) events_list = QTAILQ_HEAD_INITIALIZER(events_list);
-static unsigned int read_event_kind = -1;
-static uint64_t read_id = -1;
-static int read_checkpoint = -1;
-
 static bool events_enabled;
 
 /* Functions */
@@ -67,7 +63,9 @@ static void replay_run_event(Event *event)
 
 void replay_enable_events(void)
 {
-    events_enabled = true;
+    if (replay_mode != REPLAY_MODE_NONE) {
+        events_enabled = true;
+    }
 }
 
 bool replay_has_events(void)
@@ -77,16 +75,14 @@ bool replay_has_events(void)
 
 void replay_flush_events(void)
 {
-    replay_mutex_lock();
+    g_assert(replay_mutex_locked());
+
     while (!QTAILQ_EMPTY(&events_list)) {
         Event *event = QTAILQ_FIRST(&events_list);
-        replay_mutex_unlock();
         replay_run_event(event);
-        replay_mutex_lock();
         QTAILQ_REMOVE(&events_list, event, events);
         g_free(event);
     }
-    replay_mutex_unlock();
 }
 
 void replay_disable_events(void)
@@ -100,14 +96,14 @@ void replay_disable_events(void)
 
 void replay_clear_events(void)
 {
-    replay_mutex_lock();
+    g_assert(replay_mutex_locked());
+
     while (!QTAILQ_EMPTY(&events_list)) {
         Event *event = QTAILQ_FIRST(&events_list);
         QTAILQ_REMOVE(&events_list, event, events);
 
         g_free(event);
     }
-    replay_mutex_unlock();
 }
 
 /*! Adds specified async event to the queue */
@@ -134,14 +130,13 @@ void replay_add_event(ReplayAsyncEventKind event_kind,
     event->opaque2 = opaque2;
     event->id = id;
 
-    replay_mutex_lock();
+    g_assert(replay_mutex_locked());
     QTAILQ_INSERT_TAIL(&events_list, event, events);
-    replay_mutex_unlock();
 }
 
 void replay_bh_schedule_event(QEMUBH *bh)
 {
-    if (replay_mode != REPLAY_MODE_NONE && events_enabled) {
+    if (events_enabled) {
         uint64_t id = replay_get_current_step();
         replay_add_event(REPLAY_ASYNC_EVENT_BH, bh, NULL, id);
     } else {
@@ -161,7 +156,7 @@ void replay_add_input_sync_event(void)
 
 void replay_block_event(QEMUBH *bh, uint64_t id)
 {
-    if (replay_mode != REPLAY_MODE_NONE && events_enabled) {
+    if (events_enabled) {
         replay_add_event(REPLAY_ASYNC_EVENT_BLOCK, bh, NULL, id);
     } else {
         qemu_bh_schedule(bh);
@@ -205,13 +200,12 @@ static void replay_save_event(Event *event, int checkpoint)
 /* Called with replay mutex locked */
 void replay_save_events(int checkpoint)
 {
+    g_assert(replay_mutex_locked());
+    g_assert(checkpoint != CHECKPOINT_CLOCK_WARP_START);
     while (!QTAILQ_EMPTY(&events_list)) {
         Event *event = QTAILQ_FIRST(&events_list);
         replay_save_event(event, checkpoint);
-
-        replay_mutex_unlock();
         replay_run_event(event);
-        replay_mutex_lock();
         QTAILQ_REMOVE(&events_list, event, events);
         g_free(event);
     }
@@ -220,58 +214,60 @@ void replay_save_events(int checkpoint)
 static Event *replay_read_event(int checkpoint)
 {
     Event *event;
-    if (read_event_kind == -1) {
-        read_checkpoint = replay_get_byte();
-        read_event_kind = replay_get_byte();
-        read_id = -1;
+    if (replay_state.read_event_kind == -1) {
+        replay_state.read_event_checkpoint = replay_get_byte();
+        replay_state.read_event_kind = replay_get_byte();
+        replay_state.read_event_id = -1;
         replay_check_error();
     }
 
-    if (checkpoint != read_checkpoint) {
+    if (checkpoint != replay_state.read_event_checkpoint) {
         return NULL;
     }
 
     /* Events that has not to be in the queue */
-    switch (read_event_kind) {
+    switch (replay_state.read_event_kind) {
     case REPLAY_ASYNC_EVENT_BH:
-        if (read_id == -1) {
-            read_id = replay_get_qword();
+        if (replay_state.read_event_id == -1) {
+            replay_state.read_event_id = replay_get_qword();
         }
         break;
     case REPLAY_ASYNC_EVENT_INPUT:
         event = g_malloc0(sizeof(Event));
-        event->event_kind = read_event_kind;
+        event->event_kind = replay_state.read_event_kind;
         event->opaque = replay_read_input_event();
         return event;
     case REPLAY_ASYNC_EVENT_INPUT_SYNC:
         event = g_malloc0(sizeof(Event));
-        event->event_kind = read_event_kind;
+        event->event_kind = replay_state.read_event_kind;
         event->opaque = 0;
         return event;
     case REPLAY_ASYNC_EVENT_CHAR_READ:
         event = g_malloc0(sizeof(Event));
-        event->event_kind = read_event_kind;
+        event->event_kind = replay_state.read_event_kind;
         event->opaque = replay_event_char_read_load();
         return event;
     case REPLAY_ASYNC_EVENT_BLOCK:
-        if (read_id == -1) {
-            read_id = replay_get_qword();
+        if (replay_state.read_event_id == -1) {
+            replay_state.read_event_id = replay_get_qword();
         }
         break;
     case REPLAY_ASYNC_EVENT_NET:
         event = g_malloc0(sizeof(Event));
-        event->event_kind = read_event_kind;
+        event->event_kind = replay_state.read_event_kind;
         event->opaque = replay_event_net_load();
         return event;
     default:
-        error_report("Unknown ID %d of replay event", read_event_kind);
+        error_report("Unknown ID %d of replay event",
+            replay_state.read_event_kind);
         exit(1);
         break;
     }
 
     QTAILQ_FOREACH(event, &events_list, events) {
-        if (event->event_kind == read_event_kind
-            && (read_id == -1 || read_id == event->id)) {
+        if (event->event_kind == replay_state.read_event_kind
+            && (replay_state.read_event_id == -1
+                || replay_state.read_event_id == event->id)) {
             break;
         }
     }
@@ -290,24 +286,23 @@ static Event *replay_read_event(int checkpoint)
 /* Called with replay mutex locked */
 void replay_read_events(int checkpoint)
 {
+    g_assert(replay_mutex_locked());
     while (replay_state.data_kind == EVENT_ASYNC) {
         Event *event = replay_read_event(checkpoint);
         if (!event) {
             break;
         }
-        replay_mutex_unlock();
+        replay_finish_event();
+        replay_state.read_event_kind = -1;
         replay_run_event(event);
-        replay_mutex_lock();
 
         g_free(event);
-        replay_finish_event();
-        read_event_kind = -1;
     }
 }
 
 void replay_init_events(void)
 {
-    read_event_kind = -1;
+    replay_state.read_event_kind = -1;
 }
 
 void replay_finish_events(void)
diff --git a/replay/replay-internal.c b/replay/replay-internal.c
index fca8514012..b077cb5fd5 100644
--- a/replay/replay-internal.c
+++ b/replay/replay-internal.c
@@ -24,12 +24,23 @@
 static QemuMutex lock;
 
 /* File for replay writing */
+static bool write_error;
 FILE *replay_file;
 
+static void replay_write_error(void)
+{
+    if (!write_error) {
+        error_report("replay write error");
+        write_error = true;
+    }
+}
+
 void replay_put_byte(uint8_t byte)
 {
     if (replay_file) {
-        putc(byte, replay_file);
+        if (putc(byte, replay_file) == EOF) {
+            replay_write_error();
+        }
     }
 }
 
@@ -62,7 +73,9 @@ void replay_put_array(const uint8_t *buf, size_t size)
 {
     if (replay_file) {
         replay_put_dword(size);
-        fwrite(buf, 1, size, replay_file);
+        if (fwrite(buf, 1, size, replay_file) != size) {
+            replay_write_error();
+        }
     }
 }
 
@@ -169,31 +182,46 @@ void replay_finish_event(void)
     replay_fetch_data_kind();
 }
 
+static __thread bool replay_locked;
+
 void replay_mutex_init(void)
 {
     qemu_mutex_init(&lock);
+    /* Hold the mutex while we start-up */
+    qemu_mutex_lock(&lock);
+    replay_locked = true;
 }
 
-void replay_mutex_destroy(void)
+bool replay_mutex_locked(void)
 {
-    qemu_mutex_destroy(&lock);
+    return replay_locked;
 }
 
+/* Ordering constraints, replay_lock must be taken before BQL */
 void replay_mutex_lock(void)
 {
-    qemu_mutex_lock(&lock);
+    if (replay_mode != REPLAY_MODE_NONE) {
+        g_assert(!qemu_mutex_iothread_locked());
+        g_assert(!replay_mutex_locked());
+        qemu_mutex_lock(&lock);
+        replay_locked = true;
+    }
 }
 
 void replay_mutex_unlock(void)
 {
-    qemu_mutex_unlock(&lock);
+    if (replay_mode != REPLAY_MODE_NONE) {
+        g_assert(replay_mutex_locked());
+        replay_locked = false;
+        qemu_mutex_unlock(&lock);
+    }
 }
 
 /*! Saves cached instructions. */
 void replay_save_instructions(void)
 {
     if (replay_file && replay_mode == REPLAY_MODE_RECORD) {
-        replay_mutex_lock();
+        g_assert(replay_mutex_locked());
         int diff = (int)(replay_get_current_step() - replay_state.current_step);
 
         /* Time can only go forward */
@@ -204,6 +232,5 @@ void replay_save_instructions(void)
             replay_put_dword(diff);
             replay_state.current_step += diff;
         }
-        replay_mutex_unlock();
     }
 }
diff --git a/replay/replay-internal.h b/replay/replay-internal.h
index 3ebb19912a..ac4b27b674 100644
--- a/replay/replay-internal.h
+++ b/replay/replay-internal.h
@@ -12,7 +12,7 @@
  *
  */
 
-
+/* Any changes to order/number of events will need to bump REPLAY_VERSION */
 enum ReplayEvents {
     /* for instruction event */
     EVENT_INSTRUCTION,
@@ -78,6 +78,14 @@ typedef struct ReplayState {
         This counter is global, because requests from different
         block devices should not get overlapping ids. */
     uint64_t block_request_id;
+    /*! Prior value of the host clock */
+    uint64_t host_clock_last;
+    /*! Asynchronous event type read from the log */
+    int32_t read_event_kind;
+    /*! Asynchronous event id read from the log */
+    uint64_t read_event_id;
+    /*! Asynchronous event checkpoint id read from the log */
+    int32_t read_event_checkpoint;
 } ReplayState;
 extern ReplayState replay_state;
 
@@ -98,12 +106,11 @@ int64_t replay_get_qword(void);
 void replay_get_array(uint8_t *buf, size_t *size);
 void replay_get_array_alloc(uint8_t **buf, size_t *size);
 
-/* Mutex functions for protecting replay log file */
+/* Mutex functions for protecting replay log file and ensuring
+ * synchronisation between vCPU and main-loop threads. */
 
 void replay_mutex_init(void);
-void replay_mutex_destroy(void);
-void replay_mutex_lock(void);
-void replay_mutex_unlock(void);
+bool replay_mutex_locked(void);
 
 /*! Checks error status of the file. */
 void replay_check_error(void);
diff --git a/replay/replay-snapshot.c b/replay/replay-snapshot.c
index b2e10769a6..2ab85cfc60 100644
--- a/replay/replay-snapshot.c
+++ b/replay/replay-snapshot.c
@@ -25,6 +25,7 @@ static int replay_pre_save(void *opaque)
 {
     ReplayState *state = opaque;
     state->file_offset = ftell(replay_file);
+    state->host_clock_last = qemu_clock_get_last(QEMU_CLOCK_HOST);
 
     return 0;
 }
@@ -33,6 +34,7 @@ static int replay_post_load(void *opaque, int version_id)
 {
     ReplayState *state = opaque;
     fseek(replay_file, state->file_offset, SEEK_SET);
+    qemu_clock_set_last(QEMU_CLOCK_HOST, state->host_clock_last);
     /* If this was a vmstate, saved in recording mode,
        we need to initialize replay data fields. */
     replay_fetch_data_kind();
@@ -54,6 +56,10 @@ static const VMStateDescription vmstate_replay = {
         VMSTATE_UINT32(has_unread_data, ReplayState),
         VMSTATE_UINT64(file_offset, ReplayState),
         VMSTATE_UINT64(block_request_id, ReplayState),
+        VMSTATE_UINT64(host_clock_last, ReplayState),
+        VMSTATE_INT32(read_event_kind, ReplayState),
+        VMSTATE_UINT64(read_event_id, ReplayState),
+        VMSTATE_INT32(read_event_checkpoint, ReplayState),
         VMSTATE_END_OF_LIST()
     },
 };
@@ -83,3 +89,9 @@ void replay_vmstate_init(void)
         }
     }
 }
+
+bool replay_can_snapshot(void)
+{
+    return replay_mode == REPLAY_MODE_NONE
+        || !replay_has_events();
+}
diff --git a/replay/replay-time.c b/replay/replay-time.c
index f70382a88f..6a7565ec8d 100644
--- a/replay/replay-time.c
+++ b/replay/replay-time.c
@@ -17,13 +17,13 @@
 
 int64_t replay_save_clock(ReplayClockKind kind, int64_t clock)
 {
-    replay_save_instructions();
 
     if (replay_file) {
-        replay_mutex_lock();
+        g_assert(replay_mutex_locked());
+
+        replay_save_instructions();
         replay_put_event(EVENT_CLOCK + kind);
         replay_put_qword(clock);
-        replay_mutex_unlock();
     }
 
     return clock;
@@ -46,16 +46,16 @@ void replay_read_next_clock(ReplayClockKind kind)
 /*! Reads next clock event from the input. */
 int64_t replay_read_clock(ReplayClockKind kind)
 {
+    g_assert(replay_file && replay_mutex_locked());
+
     replay_account_executed_instructions();
 
     if (replay_file) {
         int64_t ret;
-        replay_mutex_lock();
         if (replay_next_event_is(EVENT_CLOCK + kind)) {
             replay_read_next_clock(kind);
         }
         ret = replay_state.cached_clock[kind];
-        replay_mutex_unlock();
 
         return ret;
     }
diff --git a/replay/replay.c b/replay/replay.c
index 7a23c62d61..8228261401 100644
--- a/replay/replay.c
+++ b/replay/replay.c
@@ -22,7 +22,7 @@
 
 /* Current version of the replay mechanism.
    Increase it when file format changes. */
-#define REPLAY_VERSION              0xe02006
+#define REPLAY_VERSION              0xe02007
 /* Size of replay log header */
 #define HEADER_SIZE                 (sizeof(uint32_t) + sizeof(uint64_t))
 
@@ -81,7 +81,7 @@ int replay_get_instructions(void)
 void replay_account_executed_instructions(void)
 {
     if (replay_mode == REPLAY_MODE_PLAY) {
-        replay_mutex_lock();
+        g_assert(replay_mutex_locked());
         if (replay_state.instructions_count > 0) {
             int count = (int)(replay_get_current_step()
                               - replay_state.current_step);
@@ -100,24 +100,22 @@ void replay_account_executed_instructions(void)
                 qemu_notify_event();
             }
         }
-        replay_mutex_unlock();
     }
 }
 
 bool replay_exception(void)
 {
+
     if (replay_mode == REPLAY_MODE_RECORD) {
+        g_assert(replay_mutex_locked());
         replay_save_instructions();
-        replay_mutex_lock();
         replay_put_event(EVENT_EXCEPTION);
-        replay_mutex_unlock();
         return true;
     } else if (replay_mode == REPLAY_MODE_PLAY) {
+        g_assert(replay_mutex_locked());
         bool res = replay_has_exception();
         if (res) {
-            replay_mutex_lock();
             replay_finish_event();
-            replay_mutex_unlock();
         }
         return res;
     }
@@ -129,10 +127,9 @@ bool replay_has_exception(void)
 {
     bool res = false;
     if (replay_mode == REPLAY_MODE_PLAY) {
+        g_assert(replay_mutex_locked());
         replay_account_executed_instructions();
-        replay_mutex_lock();
         res = replay_next_event_is(EVENT_EXCEPTION);
-        replay_mutex_unlock();
     }
 
     return res;
@@ -141,17 +138,15 @@ bool replay_has_exception(void)
 bool replay_interrupt(void)
 {
     if (replay_mode == REPLAY_MODE_RECORD) {
+        g_assert(replay_mutex_locked());
         replay_save_instructions();
-        replay_mutex_lock();
         replay_put_event(EVENT_INTERRUPT);
-        replay_mutex_unlock();
         return true;
     } else if (replay_mode == REPLAY_MODE_PLAY) {
+        g_assert(replay_mutex_locked());
         bool res = replay_has_interrupt();
         if (res) {
-            replay_mutex_lock();
             replay_finish_event();
-            replay_mutex_unlock();
         }
         return res;
     }
@@ -163,10 +158,9 @@ bool replay_has_interrupt(void)
 {
     bool res = false;
     if (replay_mode == REPLAY_MODE_PLAY) {
+        g_assert(replay_mutex_locked());
         replay_account_executed_instructions();
-        replay_mutex_lock();
         res = replay_next_event_is(EVENT_INTERRUPT);
-        replay_mutex_unlock();
     }
     return res;
 }
@@ -174,25 +168,35 @@ bool replay_has_interrupt(void)
 void replay_shutdown_request(ShutdownCause cause)
 {
     if (replay_mode == REPLAY_MODE_RECORD) {
-        replay_mutex_lock();
+        g_assert(replay_mutex_locked());
         replay_put_event(EVENT_SHUTDOWN + cause);
-        replay_mutex_unlock();
     }
 }
 
 bool replay_checkpoint(ReplayCheckpoint checkpoint)
 {
     bool res = false;
+    static bool in_checkpoint;
     assert(EVENT_CHECKPOINT + checkpoint <= EVENT_CHECKPOINT_LAST);
-    replay_save_instructions();
 
     if (!replay_file) {
         return true;
     }
 
-    replay_mutex_lock();
+    if (in_checkpoint) {
+        /* If we are already in checkpoint, then there is no need
+           for additional synchronization.
+           Recursion occurs when HW event modifies timers.
+           Timer modification may invoke the checkpoint and
+           proceed to recursion. */
+        return true;
+    }
+    in_checkpoint = true;
+
+    replay_save_instructions();
 
     if (replay_mode == REPLAY_MODE_PLAY) {
+        g_assert(replay_mutex_locked());
         if (replay_next_event_is(EVENT_CHECKPOINT + checkpoint)) {
             replay_finish_event();
         } else if (replay_state.data_kind != EVENT_ASYNC) {
@@ -205,12 +209,18 @@ bool replay_checkpoint(ReplayCheckpoint checkpoint)
            checkpoint were processed */
         res = replay_state.data_kind != EVENT_ASYNC;
     } else if (replay_mode == REPLAY_MODE_RECORD) {
+        g_assert(replay_mutex_locked());
         replay_put_event(EVENT_CHECKPOINT + checkpoint);
-        replay_save_events(checkpoint);
+        /* This checkpoint belongs to several threads.
+           Processing events from different threads is
+           non-deterministic */
+        if (checkpoint != CHECKPOINT_CLOCK_WARP_START) {
+            replay_save_events(checkpoint);
+        }
         res = true;
     }
 out:
-    replay_mutex_unlock();
+    in_checkpoint = false;
     return res;
 }
 
@@ -233,8 +243,6 @@ static void replay_enable(const char *fname, int mode)
 
     atexit(replay_finish);
 
-    replay_mutex_init();
-
     replay_file = fopen(fname, fmode);
     if (replay_file == NULL) {
         fprintf(stderr, "Replay: open %s: %s\n", fname, strerror(errno));
@@ -242,8 +250,9 @@ static void replay_enable(const char *fname, int mode)
     }
 
     replay_filename = g_strdup(fname);
-
     replay_mode = mode;
+    replay_mutex_init();
+
     replay_state.data_kind = -1;
     replay_state.instructions_count = 0;
     replay_state.current_step = 0;
@@ -358,7 +367,6 @@ void replay_finish(void)
     replay_snapshot = NULL;
 
     replay_finish_events();
-    replay_mutex_destroy();
 }
 
 void replay_add_blocker(Error *reason)