On 5/31/23 08:37, Xia, Chenbo wrote:
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?
I don't think so, the purpose of the access_lock is not to make the datapath threads-safe, but to protect the datapath from metadata changes by the control path. Thanks, Maxime
Thanks, Chenbo
