Re: [Qemu-devel] [PATCH v3] libvhost-user-glib: fix VugDev main fd cleanup

["Marc-André Lureau" <marcandre.lureau@redhat.com>]

Hi

On Tue, Aug 27, 2019 at 4:49 PM Johannes Berg <johannes@sipsolutions.net> wrote:
>
> From: Johannes Berg <johannes.berg@intel.com>
>
> If you try to make a device implementation that can handle multiple
> connections and allow disconnections (which requires overriding the
> VHOST_USER_NONE handling), then glib will warn that we remove a src
> while it's still on the mainloop, and will poll() an FD that doesn't
> exist anymore.
>
> Fix this by making vug_source_new() require pairing with the new
> vug_source_destroy() so we can keep the GSource referenced in the
> meantime.
>
> Note that this requires calling the new API in vhost-user-input.
> vhost-user-gpu also uses vug_source_new(), but never seems to free
> the result at all, so I haven't changed anything there.
>
> Fixes: 8bb7ddb78a1c ("libvhost-user: add glib source helper")
> Signed-off-by: Johannes Berg <johannes.berg@intel.com>
> ---
>  contrib/libvhost-user/libvhost-user-glib.c | 15 ++++++++++++---
>  contrib/libvhost-user/libvhost-user-glib.h |  1 +
>  contrib/vhost-user-input/main.c            |  6 ++----
>  3 files changed, 15 insertions(+), 7 deletions(-)
>
> diff --git a/contrib/libvhost-user/libvhost-user-glib.c b/contrib/libvhost-user/libvhost-user-glib.c
> index 99edd2f3de45..eaf88b8aa749 100644
> --- a/contrib/libvhost-user/libvhost-user-glib.c
> +++ b/contrib/libvhost-user/libvhost-user-glib.c
> @@ -91,7 +91,6 @@ vug_source_new(VugDev *gdev, int fd, GIOCondition cond,
>      g_source_add_poll(gsrc, &src->gfd);
>      id = g_source_attach(gsrc, NULL);
>      g_assert(id);
> -    g_source_unref(gsrc);
>
>      return gsrc;
>  }
> @@ -131,6 +130,16 @@ static void vug_watch(VuDev *dev, int condition, void *data)
>      }
>  }
>
> +void vug_source_destroy(GSource *src)
> +{
> +    if (!src) {
> +        return;
> +    }
> +
> +    g_source_unref(src);
> +    g_source_destroy(src);

I would call destroy() (detach) before unref().

> +}
> +
>  bool
>  vug_init(VugDev *dev, uint16_t max_queues, int socket,
>           vu_panic_cb panic, const VuDevIface *iface)
> @@ -144,7 +153,7 @@ vug_init(VugDev *dev, uint16_t max_queues, int socket,
>      }
>
>      dev->fdmap = g_hash_table_new_full(NULL, NULL, NULL,
> -                                       (GDestroyNotify) g_source_destroy);
> +                                       (GDestroyNotify) vug_source_destroy);
>
>      dev->src = vug_source_new(dev, socket, G_IO_IN, vug_watch, NULL);
>
> @@ -157,5 +166,5 @@ vug_deinit(VugDev *dev)
>      g_assert(dev);
>
>      g_hash_table_unref(dev->fdmap);
> -    g_source_unref(dev->src);
> +    vug_source_destroy(dev->src);
>  }
> diff --git a/contrib/libvhost-user/libvhost-user-glib.h b/contrib/libvhost-user/libvhost-user-glib.h
> index 64d539d93aba..1a79a4916ef2 100644
> --- a/contrib/libvhost-user/libvhost-user-glib.h
> +++ b/contrib/libvhost-user/libvhost-user-glib.h
> @@ -31,5 +31,6 @@ void vug_deinit(VugDev *dev);
>
>  GSource *vug_source_new(VugDev *dev, int fd, GIOCondition cond,
>                          vu_watch_cb vu_cb, gpointer data);
> +void vug_source_destroy(GSource *src);
>
>  #endif /* LIBVHOST_USER_GLIB_H */
> diff --git a/contrib/vhost-user-input/main.c b/contrib/vhost-user-input/main.c
> index 449fd2171a5a..7d6b0f9d80cc 100644
> --- a/contrib/vhost-user-input/main.c
> +++ b/contrib/vhost-user-input/main.c
> @@ -187,7 +187,7 @@ vi_queue_set_started(VuDev *dev, int qidx, bool started)
>      }
>
>      if (!started && vi->evsrc) {
> -        g_source_destroy(vi->evsrc);
> +        vug_source_destroy(vi->evsrc);
>          vi->evsrc = NULL;
>      }
>  }
> @@ -401,9 +401,7 @@ main(int argc, char *argv[])
>
>      vug_deinit(&vi.dev);
>
> -    if (vi.evsrc) {
> -        g_source_unref(vi.evsrc);
> -    }
> +    vugg_source_destroy(vi.evsrc);

typo

>      g_array_free(vi.config, TRUE);
>      g_free(vi.queue);
>      return 0;

vhost-user-input calls g_source_destroy(), please replace it too with
vug_source_destroy().

vhost-user-gpu "renderer_source" leaks, not this patch fault, but
worth to mention in the commit. Feel free to add a second commit to
fix that too.