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replay: synchronize on every virtual timer callback

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Sometimes virtual timer callbacks depend on order
of virtual timer processing and warping of virtual clock.
Therefore every callback should be logged to make replay deterministic.
This patch creates a checkpoint before every virtual timer callback.
With these checkpoints virtual timers processing and clock warping
events order is completely deterministic.

Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
Acked-by: Alex Bennée <alex.bennee@linaro.org>

--

v2:
  - remove mutex lock/unlock for virtual clock checkpoint since it is
    not process any asynchronous events (commit ca9759c2a9)
  - bump record/replay log file version
Message-Id: <159012932716.27256.8854065545365559921.stgit@pasha-ThinkPad-X280>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Pavel Dovgalyuk 2020-05-22 09:35:27 +03:00 • committed by Paolo Bonzini
parent 255ae6e215
commit 677a3baba4
2 changed files with 10 additions and 24 deletions
Download patch file Download diff file Expand all files Collapse all files

2
replay/replay.c
View file

@ -22,7 +22,7 @@
/* Current version of the replay mechanism. /* Current version of the replay mechanism.
Increase it when file format changes. */ Increase it when file format changes. */
#define REPLAY_VERSION 0xe02009 #define REPLAY_VERSION 0xe0200a
/* Size of replay log header */ /* Size of replay log header */
#define HEADER_SIZE (sizeof(uint32_t) + sizeof(uint64_t)) #define HEADER_SIZE (sizeof(uint32_t) + sizeof(uint64_t))

32
util/qemu-timer.c
View file

@ -501,7 +501,6 @@ bool timerlist_run_timers(QEMUTimerList *timer_list)
bool progress = false; bool progress = false;
QEMUTimerCB *cb; QEMUTimerCB *cb;
void *opaque; void *opaque;
bool need_replay_checkpoint = false;
if (!atomic_read(&timer_list->active_timers)) { if (!atomic_read(&timer_list->active_timers)) {
return false; return false;
@ -517,16 +516,6 @@ bool timerlist_run_timers(QEMUTimerList *timer_list)
break; break;
default: default:
case QEMU_CLOCK_VIRTUAL: case QEMU_CLOCK_VIRTUAL:
if (replay_mode != REPLAY_MODE_NONE) {
/* Checkpoint for virtual clock is redundant in cases where
* it's being triggered with only non-EXTERNAL timers, because
* these timers don't change guest state directly.
* Since it has conditional dependence on specific timers, it is
* subject to race conditions and requires special handling.
* See below.
*/
need_replay_checkpoint = true;
}
break; break;
case QEMU_CLOCK_HOST: case QEMU_CLOCK_HOST:
if (!replay_checkpoint(CHECKPOINT_CLOCK_HOST)) { if (!replay_checkpoint(CHECKPOINT_CLOCK_HOST)) {
@ -559,19 +548,16 @@ bool timerlist_run_timers(QEMUTimerList *timer_list)
*/ */
break; break;
} }
if (need_replay_checkpoint /* Checkpoint for virtual clock is redundant in cases where
&& !(ts->attributes & QEMU_TIMER_ATTR_EXTERNAL)) { * it's being triggered with only non-EXTERNAL timers, because
/* once we got here, checkpoint clock only once */ * these timers don't change guest state directly.
need_replay_checkpoint = false; */
if (replay_mode != REPLAY_MODE_NONE
&& timer_list->clock->type == QEMU_CLOCK_VIRTUAL
&& !(ts->attributes & QEMU_TIMER_ATTR_EXTERNAL)
&& !replay_checkpoint(CHECKPOINT_CLOCK_VIRTUAL)) {
qemu_mutex_unlock(&timer_list->active_timers_lock); qemu_mutex_unlock(&timer_list->active_timers_lock);
if (!replay_checkpoint(CHECKPOINT_CLOCK_VIRTUAL)) { goto out;
goto out;
}
qemu_mutex_lock(&timer_list->active_timers_lock);
/* The lock was released; start over again in case the list was
* modified.
*/
continue;
} }
/* remove timer from the list before calling the callback */ /* remove timer from the list before calling the callback */