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Re: [PATCH] vhost-user-input: use free(elem) instead of g_free(elem)
From: |
Daniel P . Berrangé |
Subject: |
Re: [PATCH] vhost-user-input: use free(elem) instead of g_free(elem) |
Date: |
Wed, 20 Nov 2019 11:48:56 +0000 |
User-agent: |
Mutt/1.12.1 (2019-06-15) |
On Tue, Nov 19, 2019 at 11:16:26AM +0000, Stefan Hajnoczi wrote:
> The virtqueue element returned by vu_queue_pop() is allocated using
> malloc(3) by virtqueue_alloc_element(). Use the matching free(3)
> function instead of glib's g_free().
Just as an FYI, since glib 2.46 g_malloc is hardcoded to use the
system allocator, so it is now guaranteed that g_malloc/malloc
and g_free/free are safely interchangable. I recently got this
clarified in the glib docs:
https://gitlab.gnome.org/GNOME/glib/merge_requests/1099//diffs
QEMU mandates 2.48 so we are now safe in that regard
For readability/sanity sake I'd still suggest matching functions
but it is not a functional danger any more. Even when it was a
risk, that risk only arose if you called GLib's API for installing
a custom allocator callback which QEMU never did, so it was always
a non-issue.
Where this is most helpful is in exchanging allocated data with
3rd party libraries that don't use glib. We no longer have to
worry about dup'ing memory going in/out libraries not using
glib's allocators.
>
> Signed-off-by: Stefan Hajnoczi <address@hidden>
> ---
> contrib/vhost-user-input/main.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/contrib/vhost-user-input/main.c b/contrib/vhost-user-input/main.c
> index 449fd2171a..ef4b7769f2 100644
> --- a/contrib/vhost-user-input/main.c
> +++ b/contrib/vhost-user-input/main.c
> @@ -77,7 +77,7 @@ static void vi_input_send(VuInput *vi, struct
> virtio_input_event *event)
> len = iov_from_buf(elem->in_sg, elem->in_num,
> 0, &vi->queue[i].event,
> sizeof(virtio_input_event));
> vu_queue_push(dev, vq, elem, len);
> - g_free(elem);
> + free(elem);
> }
>
> vu_queue_notify(&vi->dev.parent, vq);
> @@ -153,7 +153,7 @@ static void vi_handle_sts(VuDev *dev, int qidx)
> 0, &event, sizeof(event));
> vi_handle_status(vi, &event);
> vu_queue_push(dev, vq, elem, len);
> - g_free(elem);
> + free(elem);
> }
>
> vu_queue_notify(&vi->dev.parent, vq);
> --
> 2.23.0
>
>
Regards,
Daniel
--
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