Re: [Qemu-devel] [PATCH] do not call monitor_resume() from migrate_fd_put_buffer() error path

[Michael Tokarev <mjt@tls.msk.ru>]

So, can we decide on this somehow?  I don't see a code
path where we don't call monitor_resume at the end,
so the "intermediate" monitor_resume can be dropped.
This way we fix real bug.  If there will be other
problem from that, it can be fixed later - this will
mean that code path is found...

Should I resend the initial patch again?

Thanks,

/mjt

21.07.2011 02:06, Jan Kiszka wriote:
> On 2011-07-20 18:34, Marcelo Tosatti wrote:
>> On Tue, Jul 19, 2011 at 11:48:22PM +0200, Jan Kiszka wrote:
>>> On 2011-07-19 13:46, Michael Tokarev wrote:
>>>> If we do, it results in double monitor_resume() (second being called
>>>> from migrate_fd_cleanup() anyway) and monitor suspend count becoming
>>>> negative.
>>>>
>>>> Cc'ing people from `git blame' list for the lines in question: the
>>>> change fixes the problem but I'm not sure what the original intention
>>>> of this code was in this place.  Unfortunately noone replied to two
>>>> my attempts to raise this issue.
>>>>
>>>> Signed-Off-By: Michael Tokarev <mjt@tls.msk.ru>
>>>> ---
>>>>  migration.c |    3 ---
>>>>  1 files changed, 0 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/migration.c b/migration.c
>>>> index af3a1f2..115588c 100644
>>>> --- a/migration.c
>>>> +++ b/migration.c
>>>> @@ -330,9 +330,6 @@ ssize_t migrate_fd_put_buffer(void *opaque, const void *data, size_t size)
>>>>      if (ret == -EAGAIN) {
>>>>          qemu_set_fd_handler2(s->fd, NULL, NULL, migrate_fd_put_notify, s);
>>>>      } else if (ret < 0) {
>>>> -        if (s->mon) {
>>>> -            monitor_resume(s->mon);
>>>> -        }
>>>>          s->state = MIG_STATE_ERROR;
>>>>          notifier_list_notify(&migration_state_notifiers);
>>>>      }
>>>
>>> Looks reasonable to me, but Marcelo should comment on this, specifically
>>> which scenario once required the resume.
>>>
>>> Jan
>>
>> If the monitor was suspended (migrate without -d), then this path must
>> resume. Should record that somewhere and check here.
> 
> It's clear that we need to resume. The question is in which case
> migrate_fd_cleanup may not be called after an error in
> migrate_fd_put_buffer.
> 
> Jan
>