On Thu, 28 Jan 2021 09:48:35 -0500
Vivek Goyal <vgo...@redhat.com> wrote:
> On Thu, Jan 28, 2021 at 03:31:23PM +0100, Greg Kurz wrote:
> > On Mon, 25 Jan 2021 13:01:11 -0500
> > Vivek Goyal <vgo...@redhat.com> wrote:
> >
> > > dev->slave_mutex needs to be taken when sending messages on slave_fd.
> > > Currently _vu_queue_notify() does not do that.
> > >
> > > Introduce a helper vu_message_slave_send_receive() which sends as well
> > > as receive response. Use this helper in all the paths which send
> > > message on slave_fd channel.
> > >
> >
> > Does this fix any known bug ?
>
> I am not aware of any bug. This fix is based on code inspection.
>
> Also I wanted a central place/function to send messages on slave channel
> so that I can check state of slave channel (open/close) and act
> accordingly. Otherwise I will have to do the check at every place
> which is trying to send/receive message on slave channel.
>
Makes sense. Thanks for the clarification.
> Vivek
>
> >
> > > Signed-off-by: Vivek Goyal <vgo...@redhat.com>
> > > ---
> >
> > LGTM
> >
> > Reviewed-by: Greg Kurz <gr...@kaod.org>
> >
> > > subprojects/libvhost-user/libvhost-user.c | 50 ++++++++++++-----------
> > > 1 file changed, 27 insertions(+), 23 deletions(-)
> > >
> > > diff --git a/subprojects/libvhost-user/libvhost-user.c
> > > b/subprojects/libvhost-user/libvhost-user.c
> > > index 4cf4aef63d..7a56c56dc8 100644
> > > --- a/subprojects/libvhost-user/libvhost-user.c
> > > +++ b/subprojects/libvhost-user/libvhost-user.c
> > > @@ -403,7 +403,7 @@ vu_send_reply(VuDev *dev, int conn_fd, VhostUserMsg
> > > *vmsg)
> > > * Processes a reply on the slave channel.
> > > * Entered with slave_mutex held and releases it before exit.
> > > * Returns true on success.
> > > - * *payload is written on success
> > > + * *payload is written on success, if payload is not NULL.
> > > */
> > > static bool
> > > vu_process_message_reply(VuDev *dev, const VhostUserMsg *vmsg,
> > > @@ -427,7 +427,9 @@ vu_process_message_reply(VuDev *dev, const
> > > VhostUserMsg *vmsg,
> > > goto out;
> > > }
> > >
> > > - *payload = msg_reply.payload.u64;
> > > + if (payload) {
> > > + *payload = msg_reply.payload.u64;
> > > + }
> > > result = true;
> > >
> > > out:
> > > @@ -435,6 +437,25 @@ out:
> > > return result;
> > > }
> > >
> > > +/* Returns true on success, false otherwise */
> > > +static bool
> > > +vu_message_slave_send_receive(VuDev *dev, VhostUserMsg *vmsg, uint64_t
> > > *payload)
> > > +{
> > > + pthread_mutex_lock(&dev->slave_mutex);
> > > + if (!vu_message_write(dev, dev->slave_fd, vmsg)) {
> > > + pthread_mutex_unlock(&dev->slave_mutex);
> > > + return false;
> > > + }
> > > +
> > > + if ((vmsg->flags & VHOST_USER_NEED_REPLY_MASK) == 0) {
> > > + pthread_mutex_unlock(&dev->slave_mutex);
> > > + return true;
> > > + }
> > > +
> > > + /* Also unlocks the slave_mutex */
> > > + return vu_process_message_reply(dev, vmsg, payload);
> > > +}
> > > +
> > > /* Kick the log_call_fd if required. */
> > > static void
> > > vu_log_kick(VuDev *dev)
> > > @@ -1340,16 +1361,8 @@ bool vu_set_queue_host_notifier(VuDev *dev,
> > > VuVirtq *vq, int fd,
> > > return false;
> > > }
> > >
> > > - pthread_mutex_lock(&dev->slave_mutex);
> > > - if (!vu_message_write(dev, dev->slave_fd, &vmsg)) {
> > > - pthread_mutex_unlock(&dev->slave_mutex);
> > > - return false;
> > > - }
> > > -
> > > - /* Also unlocks the slave_mutex */
> > > - res = vu_process_message_reply(dev, &vmsg, &payload);
> > > + res = vu_message_slave_send_receive(dev, &vmsg, &payload);
> > > res = res && (payload == 0);
> > > -
> > > return res;
> > > }
> > >
> > > @@ -2395,10 +2408,7 @@ static void _vu_queue_notify(VuDev *dev, VuVirtq
> > > *vq, bool sync)
> > > vmsg.flags |= VHOST_USER_NEED_REPLY_MASK;
> > > }
> > >
> > > - vu_message_write(dev, dev->slave_fd, &vmsg);
> > > - if (ack) {
> > > - vu_message_read_default(dev, dev->slave_fd, &vmsg);
> > > - }
> > > + vu_message_slave_send_receive(dev, &vmsg, NULL);
> > > return;
> > > }
> > >
> > > @@ -2942,17 +2952,11 @@ int64_t vu_fs_cache_request(VuDev *dev,
> > > VhostUserSlaveRequest req, int fd,
> > > return -EINVAL;
> > > }
> > >
> > > - pthread_mutex_lock(&dev->slave_mutex);
> > > - if (!vu_message_write(dev, dev->slave_fd, &vmsg)) {
> > > - pthread_mutex_unlock(&dev->slave_mutex);
> > > - return -EIO;
> > > - }
> > > -
> > > - /* Also unlocks the slave_mutex */
> > > - res = vu_process_message_reply(dev, &vmsg, &payload);
> > > + res = vu_message_slave_send_receive(dev, &vmsg, &payload);
> > > if (!res) {
> > > return -EIO;
> > > }
> > > +
> > > /*
> > > * Payload is delivered as uint64_t but is actually signed for
> > > * errors.
> >
>
