From: Ilya Maximets <i.maximets@samsung.com>
To: dev@dpdk.org, Huawei Xie <huawei.xie@intel.com>,
Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: Ilya Maximets <i.maximets@samsung.com>,
Dyasly Sergey <s.dyasly@samsung.com>
Subject: [dpdk-dev] [PATCH RFC 3/4] vhost: avoid reordering of used->idx and last_used_idx updating.
Date: Fri, 19 Feb 2016 09:32:42 +0300 [thread overview]
Message-ID: <1455863563-15751-4-git-send-email-i.maximets@samsung.com> (raw)
In-Reply-To: <1455863563-15751-1-git-send-email-i.maximets@samsung.com>
Calling rte_vhost_enqueue_burst() simultaneously from different threads
for the same queue_id requires additional SMP memory barrier to avoid
reordering of used->idx and last_used_idx updates.
In case of virtio_dev_rx() memory barrier rte_mb() simply moved one
instruction higher.
Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
---
lib/librte_vhost/vhost_rxtx.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
index 9095fb1..a03f687 100644
--- a/lib/librte_vhost/vhost_rxtx.c
+++ b/lib/librte_vhost/vhost_rxtx.c
@@ -281,10 +281,13 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
rte_pause();
*(volatile uint16_t *)&vq->used->idx += count;
- vq->last_used_idx = res_end_idx;
- /* flush used->idx update before we read avail->flags. */
+ /*
+ * Flush used->idx update to make it visible to virtio and all other
+ * threads before allowing to modify it.
+ */
rte_mb();
+ vq->last_used_idx = res_end_idx;
/* Kick the guest if necessary. */
if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT))
@@ -586,19 +589,24 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
rte_pause();
*(volatile uint16_t *)&vq->used->idx += entry_success;
+ /*
+ * Flush used->idx update to make it visible to all
+ * other threads before allowing to modify it.
+ */
+ rte_smp_wmb();
+
vq->last_used_idx = res_cur_idx;
}
merge_rx_exit:
if (likely(pkt_idx)) {
- /* flush used->idx update before we read avail->flags. */
+ /* Flush used->idx update to make it visible to virtio. */
rte_mb();
/* Kick the guest if necessary. */
if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT))
eventfd_write(vq->callfd, (eventfd_t)1);
}
-
return pkt_idx;
}
--
2.5.0
next prev parent reply other threads:[~2016-02-19 6:32 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-19 6:32 [dpdk-dev] [PATCH RFC 0/4] Thread safe rte_vhost_enqueue_burst() Ilya Maximets
2016-02-19 6:32 ` [dpdk-dev] [PATCH RFC 1/4] vhost: use SMP barriers instead of compiler ones Ilya Maximets
2016-02-19 6:32 ` [dpdk-dev] [PATCH RFC 2/4] vhost: make buf vector for scatter RX local Ilya Maximets
2016-02-19 7:06 ` Yuanhan Liu
2016-02-19 7:30 ` Ilya Maximets
2016-02-19 8:10 ` Xie, Huawei
2016-04-05 5:47 ` [dpdk-dev] [RFC] vhost-user public struct refactor (was Re: [PATCH RFC 2/4] vhost: make buf vector for scatter RX) local Yuanhan Liu
2016-04-05 8:37 ` Thomas Monjalon
2016-04-05 14:06 ` Yuanhan Liu
2016-04-06 4:14 ` Flavio Leitner
2016-04-06 4:54 ` Yuanhan Liu
2016-02-19 6:32 ` Ilya Maximets [this message]
2016-02-19 6:32 ` [dpdk-dev] [PATCH RFC 4/4] doc: add note about rte_vhost_enqueue_burst thread safety Ilya Maximets
2016-02-19 7:10 ` Yuanhan Liu
2016-02-19 8:36 ` Xie, Huawei
2016-02-19 9:05 ` Ilya Maximets
2016-02-22 2:07 ` Xie, Huawei
2016-02-22 10:14 ` Thomas Monjalon
2016-02-23 5:56 ` Xie, Huawei
2016-02-24 5:06 ` Ilya Maximets
2016-02-25 5:12 ` Xie, Huawei
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