Re: [Qemu-block] [PATCH 16/20] qemu-img: call aio_context_acquire/release around block job

[Paolo Bonzini]

On 19/10/2016 02:54, Fam Zheng wrote:
> On Mon, 10/17 15:54, Paolo Bonzini wrote:
>> This will be needed by bdrv_reopen_multiple, which calls
>> bdrv_drain_all and thus will *release* the AioContext.
> 
> Looks okay, but I wonder how bdrv_drain_all releasing AioContext break 
> anything?

If you don't acquire it first, you get an assertion failure for
releasing a mutex you haven't acquired yet.

Initially I made aio_context_acquire a nop for the default QEMU context,
but then decided it was a hack.

Paolo

> Fam
> 
>>
>> Signed-off-by: Paolo Bonzini <address@hidden>
>> ---
>>         v1->v2: new [qemu-iotests]
>>
>>  qemu-img.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/qemu-img.c b/qemu-img.c
>> index 02c07b9..ad7c964 100644
>> --- a/qemu-img.c
>> +++ b/qemu-img.c
>> @@ -795,6 +795,7 @@ static void run_block_job(BlockJob *job, Error **errp)
>>  {
>>      AioContext *aio_context = blk_get_aio_context(job->blk);
>>  
>> +    aio_context_acquire(aio_context);
>>      do {
>>          aio_poll(aio_context, true);
>>          qemu_progress_print(job->len ?
>> @@ -802,6 +803,7 @@ static void run_block_job(BlockJob *job, Error **errp)
>>      } while (!job->ready);
>>  
>>      block_job_complete_sync(job, errp);
>> +    aio_context_release(aio_context);
>>  
>>      /* A block job may finish instantaneously without publishing any 
>> progress,
>>       * so just signal completion here */
>> @@ -819,6 +821,7 @@ static int img_commit(int argc, char **argv)
>>      Error *local_err = NULL;
>>      CommonBlockJobCBInfo cbi;
>>      bool image_opts = false;
>> +    AioContext *aio_context;
>>  
>>      fmt = NULL;
>>      cache = BDRV_DEFAULT_CACHE;
>> @@ -928,8 +931,11 @@ static int img_commit(int argc, char **argv)
>>          .bs   = bs,
>>      };
>>  
>> +    aio_context = bdrv_get_aio_context(bs);
>> +    aio_context_acquire(aio_context);
>>      commit_active_start("commit", bs, base_bs, 0, BLOCKDEV_ON_ERROR_REPORT,
>>                          common_block_job_cb, &cbi, &local_err, false);
>> +    aio_context_release(aio_context);
>>      if (local_err) {
>>          goto done;
>>      }
>> -- 
>> 2.7.4
>>
>>