Hi Eelco,
> -----Original Message-----
> From: Eelco Chaudron <echau...@redhat.com>
> Sent: Wednesday, May 17, 2023 5:09 PM
> To: maxime.coque...@redhat.com; Xia, Chenbo <chenbo....@intel.com>;
> david.march...@redhat.com
> Cc: dev@dpdk.org
> Subject: [PATCH v3 1/4] vhost: change vhost_virtqueue access lock to a
> read/write one
>
> This change will allow the vhost interrupt datapath handling to be split
> between two processed without one of them holding an explicit lock.
>
> Signed-off-by: Eelco Chaudron <echau...@redhat.com>
> ---
> lib/eal/include/generic/rte_rwlock.h | 17 ++++++
> lib/vhost/vhost.c | 46 +++++++++--------
> lib/vhost/vhost.h | 4 +-
> lib/vhost/vhost_user.c | 14 +++--
> lib/vhost/virtio_net.c | 90 +++++++++++++++++------------
> -----
> 5 files changed, 94 insertions(+), 77 deletions(-)
>
> diff --git a/lib/eal/include/generic/rte_rwlock.h
> b/lib/eal/include/generic/rte_rwlock.h
> index 71e2d8d5f4..9e083bbc61 100644
> --- a/lib/eal/include/generic/rte_rwlock.h
> +++ b/lib/eal/include/generic/rte_rwlock.h
> @@ -236,6 +236,23 @@ rte_rwlock_write_unlock(rte_rwlock_t *rwl)
> __atomic_fetch_sub(&rwl->cnt, RTE_RWLOCK_WRITE, __ATOMIC_RELEASE);
> }
>
> +/**
> + * Test if the write lock is taken.
> + *
> + * @param rwl
> + * A pointer to a rwlock structure.
> + * @return
> + * 1 if the write lock is currently taken; 0 otherwise.
> + */
> +static inline int
> +rte_rwlock_write_is_locked(rte_rwlock_t *rwl)
> +{
> + if (__atomic_load_n(&rwl->cnt, __ATOMIC_RELAXED) & RTE_RWLOCK_WRITE)
> + return 1;
> +
> + return 0;
> +}
> +
Again we need to update release note as it's a new EAL API.
> /**
> * Try to execute critical section in a hardware memory transaction, if
> it
> * fails or not available take a read lock
> diff --git a/lib/vhost/vhost.c b/lib/vhost/vhost.c
> index ef37943817..74bdbfd810 100644
> --- a/lib/vhost/vhost.c
> +++ b/lib/vhost/vhost.c
> @@ -393,9 +393,9 @@ free_vq(struct virtio_net *dev, struct vhost_virtqueue
> *vq)
> else
> rte_free(vq->shadow_used_split);
>
> - rte_spinlock_lock(&vq->access_lock);
> + rte_rwlock_write_lock(&vq->access_lock);
> vhost_free_async_mem(vq);
> - rte_spinlock_unlock(&vq->access_lock);
> + rte_rwlock_write_unlock(&vq->access_lock);
> rte_free(vq->batch_copy_elems);
> vhost_user_iotlb_destroy(vq);
> rte_free(vq->log_cache);
> @@ -630,7 +630,7 @@ alloc_vring_queue(struct virtio_net *dev, uint32_t
> vring_idx)
>
> dev->virtqueue[i] = vq;
> init_vring_queue(dev, vq, i);
> - rte_spinlock_init(&vq->access_lock);
> + rte_rwlock_init(&vq->access_lock);
> vq->avail_wrap_counter = 1;
> vq->used_wrap_counter = 1;
> vq->signalled_used_valid = false;
> @@ -1305,14 +1305,14 @@ rte_vhost_vring_call(int vid, uint16_t vring_idx)
> if (!vq)
> return -1;
>
> - rte_spinlock_lock(&vq->access_lock);
> + rte_rwlock_read_lock(&vq->access_lock);
>
> if (vq_is_packed(dev))
> vhost_vring_call_packed(dev, vq);
> else
> vhost_vring_call_split(dev, vq);
>
> - rte_spinlock_unlock(&vq->access_lock);
> + rte_rwlock_read_unlock(&vq->access_lock);
Not sure about this. vhost_ring_call_packed/split is changing some field in
Vq. Should we use write lock here?
Thanks,
Chenbo
