replay: push replay_mutex_lock up the call tree

Now instead of using the replay_lock to guard the output of the log we
now use it to protect the whole execution section. This replaces what
the BQL used to do when it was held during TCG execution.

We also introduce some rules for locking order - mainly that you
cannot take the replay_mutex while holding the BQL. This leads to some
slight sophistry during start-up and extending the
replay_mutex_destroy function to unlock the mutex without checking
for the BQL condition so it can be cleanly dropped in the non-replay
case.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Tested-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Message-Id: <20180227095248.1060.40374.stgit@pasha-VirtualBox>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

1 files changed, 13 insertions, 21 deletions

diff --git a/replay/replay.c b/replay/replay.c
index 5d05ee0..90f98b7 100644
--- a/replay/replay.c
+++ b/replay/replay.c
@@ -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;
 }
@@ -174,9 +168,8 @@ 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();
     }
 }
 
@@ -190,9 +183,9 @@ bool replay_checkpoint(ReplayCheckpoint checkpoint)
         return true;
     }
 
-    replay_mutex_lock();
 
     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 +198,12 @@ 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);
         res = true;
     }
 out:
-    replay_mutex_unlock();
     return res;
 }
 
@@ -233,8 +226,6 @@ 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 +233,9 @@ 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;