Re: [RFC PATCH v2 2/6] migration/multifd: Stop checking p->quit in multifd_send_thread

[Fabiano Rosas <farosas@suse.de>]

Juan Quintela <quintela@redhat.com> writes:

> Fabiano Rosas <farosas@suse.de> wrote:
>> We don't need to check p->quit in the multifd_send_thread() because it
>> is shadowed by the 'exiting' flag. Ever since that flag was added
>> p->quit became obsolete as a way to stop the thread.
>>
>> Since p->quit is set at multifd_send_terminate_threads() under the
>> p->mutex lock, the thread will only see it once it loops, so 'exiting'
>> will always be seen first.
>>
>> Note that setting p->quit at multifd_send_terminate_threads() still
>> makes sense because we need a way to inform multifd_send_pages() that
>> the channel has stopped.
>>
>> Signed-off-by: Fabiano Rosas <farosas@suse.de>
>
> Reviewed-by: Juan Quintela <quintela@redhat.com>
>
> But then should we remove the quit altogether?
>

It still serves a purpose to allow multifd_send_pages() to see that the
channel has exited. While that function does also check
multifd_send_state->exiting, it could already be waiting at the mutex
when the channel aborts. So we need to either check 'exiting' again or
keep p->quit.