Re: [for-5.0 PATCH 08/11] replay: flush rr queue before loading the vmstate

["Alex Bennée" <alex.bennee@linaro.org>]

Pavel Dovgalyuk <pavel.dovgaluk@gmail.com> writes:

> From: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
>
> Non-empty record/replay queue prevents saving and loading the VM state,
> because it includes pending bottom halves and block coroutines.
> But when the new VM state is loaded, we don't have to preserve the consistency
> of the current state anymore. Therefore this patch just flushes the queue
> allowing the coroutines to finish and removes checking for empty rr queue
> for load_snapshot function.
>
> Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
> ---
>  include/sysemu/replay.h  |    2 ++
>  migration/savevm.c       |   12 ++++++------
>  replay/replay-internal.h |    2 --
>  3 files changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/include/sysemu/replay.h b/include/sysemu/replay.h
> index e00ed2f4a5..239c01e7df 100644
> --- a/include/sysemu/replay.h
> +++ b/include/sysemu/replay.h
> @@ -149,6 +149,8 @@ void replay_disable_events(void);
>  void replay_enable_events(void);
>  /*! Returns true when saving events is enabled */
>  bool replay_events_enabled(void);
> +/* Flushes events queue */
> +void replay_flush_events(void);
>  /*! Adds bottom half event to the queue */
>  void replay_bh_schedule_event(QEMUBH *bh);
>  /* Adds oneshot bottom half event to the queue */
> diff --git a/migration/savevm.c b/migration/savevm.c
> index ae84bf6ab0..0c5cac372a 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -2834,12 +2834,6 @@ int load_snapshot(const char *name, Error **errp)
>      AioContext *aio_context;
>      MigrationIncomingState *mis = migration_incoming_get_current();
>  
> -    if (!replay_can_snapshot()) {
> -        error_setg(errp, "Record/replay does not allow loading snapshot "
> -                   "right now. Try once more later.");
> -        return -EINVAL;
> -    }
> -
>      if (!bdrv_all_can_snapshot(&bs)) {
>          error_setg(errp,
>                     "Device '%s' is writable but does not support snapshots",
> @@ -2873,6 +2867,12 @@ int load_snapshot(const char *name, Error **errp)
>          return -EINVAL;
>      }
>  
> +    /*
> +     * Flush the record/replay queue. Now the VM state is going
> +     * to change. Therefore we don't need to preserve its consistency
> +     */
> +    replay_flush_events();
> +
<snip>

This is the commit that introduces:

  ERROR:/home/alex.bennee/lsrc/qemu.git/replay/replay-events.c:80:replay_flush_events:
  assertion failed: (replay_mutex_locked())

To the already failing:

  /bin/sh -c "cd builds/all && make -j4 && cd tests/qemu-iotests && ./check -qcow2 267"

test case.

-- 
Alex Bennée