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

[Jan Kiszka <jan.kiszka@web.de>]

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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


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