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

[Wei Yang <richardw.yang@linux.intel.com>]

On Tue, Jul 23, 2019 at 06:23:53PM +0100, Dr. David Alan Gilbert wrote:
>* 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'
>

oops,  thanks for pointing out.

>> 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

-- 
Wei Yang
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