> -----Original Message----- > From: Maxime Coquelin <[email protected]> > Sent: Monday, October 5, 2020 10:26 PM > To: Fu, Patrick <[email protected]>; [email protected]; Xia, Chenbo > <[email protected]> > Cc: Wang, Zhihong <[email protected]>; Jiang, Cheng1 > <[email protected]> > Subject: Re: [PATCH v3 4/4] vhost: fix async register/unregister deadlock > > > > On 9/29/20 11:29 AM, Patrick Fu wrote: > > When async register/unregister function is invoked in certain vhost > > event callbacks (e.g. vring state change), deadlock may occur due to > > recursive spinlock acquire. This patch removes unnecessary spinlock > > from register API and use trylock() primitive in the unregister API > > to avoid deadlock. > > I am not convinced it is unnecessary in every cases. > > > > Fixes: 78639d54563a ("vhost: introduce async enqueue registration API") > > > > Signed-off-by: Patrick Fu <[email protected]> > > --- > > lib/librte_vhost/vhost.c | 13 +++++++------ > > lib/librte_vhost/vhost_user.c | 4 ++-- > > 2 files changed, 9 insertions(+), 8 deletions(-) > > > > diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c > > index 05b578c2f..ba504a00a 100644 > > --- a/lib/librte_vhost/vhost.c > > +++ b/lib/librte_vhost/vhost.c > > @@ -1577,8 +1577,6 @@ int rte_vhost_async_channel_register(int vid, > uint16_t queue_id, > > ops->transfer_data == NULL)) > > return -1; > > > > - rte_spinlock_lock(&vq->access_lock); > > - > > What if a virtqueue is being destroyed while this function is called? >
Yes, this is a scenario that access_lock may help. I will add spinlock back in v4. Thanks, Patrick
