Re: [Qemu-devel] [PATCH] migration/postcopy: use mis->bh instead of allocating a QEMUBH

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Wei Yang (richardw.yang@linux.intel.com) wrote:
> For migration incoming side, it either quit in precopy or postcopy. It
> is save to use the mis->bh for both instead of allocating a dedicated

     ^^^^ 'safe' not 'save'

> QEMUBH for postcopy.
> 
> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>

Yes, I think that's OK; it's a little subtle.  Once postcopy is in 'run'
then the main incoming code will exit before running it's bh, so you're
right that it's free for us to use.



Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  migration/savevm.c | 17 ++++-------------
>  1 file changed, 4 insertions(+), 13 deletions(-)
> 
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 25fe7ea05a..0105068579 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -1856,16 +1856,10 @@ static int loadvm_postcopy_handle_listen(MigrationIncomingState *mis)
>      return 0;
>  }
>  
> -
> -typedef struct {
> -    QEMUBH *bh;
> -} HandleRunBhData;
> -
>  static void loadvm_postcopy_handle_run_bh(void *opaque)
>  {
>      Error *local_err = NULL;
> -    HandleRunBhData *data = opaque;
> -    MigrationIncomingState *mis = migration_incoming_get_current();
> +    MigrationIncomingState *mis = opaque;
>  
>      /* TODO we should move all of this lot into postcopy_ram.c or a shared code
>       * in migration.c
> @@ -1897,8 +1891,7 @@ static void loadvm_postcopy_handle_run_bh(void *opaque)
>          runstate_set(RUN_STATE_PAUSED);
>      }
>  
> -    qemu_bh_delete(data->bh);
> -    g_free(data);
> +    qemu_bh_delete(mis->bh);
>  }
>  
>  /* After all discards we can start running and asking for pages */
> @@ -1906,7 +1899,6 @@ static int loadvm_postcopy_handle_run(MigrationIncomingState *mis)
>  {
>      PostcopyState old_ps = POSTCOPY_INCOMING_LISTENING;
>      PostcopyState ps = postcopy_state_set(POSTCOPY_INCOMING_RUNNING, &old_ps);
> -    HandleRunBhData *data;
>  
>      trace_loadvm_postcopy_handle_run();
>      if (ps != old_ps) {
> @@ -1914,9 +1906,8 @@ static int loadvm_postcopy_handle_run(MigrationIncomingState *mis)
>          return -1;
>      }
>  
> -    data = g_new(HandleRunBhData, 1);
> -    data->bh = qemu_bh_new(loadvm_postcopy_handle_run_bh, data);
> -    qemu_bh_schedule(data->bh);
> +    mis->bh = qemu_bh_new(loadvm_postcopy_handle_run_bh, mis);
> +    qemu_bh_schedule(mis->bh);
>  
>      /* We need to finish reading the stream from the package
>       * and also stop reading anything more from the stream that loaded the
> -- 
> 2.17.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK