Re: [Qemu-devel] [PATCH v13 11/12] migration: Remove not needed semaphore and quit

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Juan Quintela (quintela@redhat.com) wrote:
> We know quit closing the QIO.

This patch does two different things; one of which I think I understand.

The 'quit' has been removed - I think that makes sense because the
multifd threads terminate when either they come to the end of a stream
or hit an error; there's no case of asking them to quit explicitly.
The 'sem' was basically for kicking the recv-thread to quit; which again
isn't needed.

Now, what about the object_unref on p->c ?
If I've got this right multifd_recv_terminate_threads is only called in
the error case; but doesn't multifd_load_cleanup also get called in that
case - it does the unref and p->c = NULL as well.

Dave

> Signed-off-by: Juan Quintela <quintela@redhat.com>
> ---
>  migration/ram.c | 11 ++---------
>  1 file changed, 2 insertions(+), 9 deletions(-)
> 
> diff --git a/migration/ram.c b/migration/ram.c
> index a707d3ae80..62eea9e02f 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -587,14 +587,10 @@ typedef struct {
>      QemuThread thread;
>      /* communication channel */
>      QIOChannel *c;
> -    /* sem where to wait for more work */
> -    QemuSemaphore sem;
>      /* this mutex protects the following parameters */
>      QemuMutex mutex;
>      /* is this channel thread running */
>      bool running;
> -    /* should this thread finish */
> -    bool quit;
>      /* array of pages to receive */
>      MultiFDPages_t *pages;
>      /* packet allocated len */
> @@ -1115,8 +1111,8 @@ static void multifd_recv_terminate_threads(Error *err)
>          MultiFDRecvParams *p = &multifd_recv_state->params[i];
>  
>          qemu_mutex_lock(&p->mutex);
> -        p->quit = true;
> -        qemu_sem_post(&p->sem);
> +        object_unref(OBJECT(p->c));
> +        p->c = NULL;
>          qemu_mutex_unlock(&p->mutex);
>      }
>  }
> @@ -1139,7 +1135,6 @@ int multifd_load_cleanup(Error **errp)
>          object_unref(OBJECT(p->c));
>          p->c = NULL;
>          qemu_mutex_destroy(&p->mutex);
> -        qemu_sem_destroy(&p->sem);
>          qemu_sem_destroy(&p->sem_sync);
>          g_free(p->name);
>          p->name = NULL;
> @@ -1262,9 +1257,7 @@ int multifd_load_setup(void)
>          MultiFDRecvParams *p = &multifd_recv_state->params[i];
>  
>          qemu_mutex_init(&p->mutex);
> -        qemu_sem_init(&p->sem, 0);
>          qemu_sem_init(&p->sem_sync, 0);
> -        p->quit = false;
>          p->id = i;
>          p->pages = multifd_pages_init(page_count);
>          p->packet_len = sizeof(MultiFDPacket_t)
> -- 
> 2.17.0
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK