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vhost: add smp_wmb() before logging used->ring

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This doesn't really fix anything as rte_vhost
logging functions are extremely poorly designed
and do smp_wmb() by themselves - but only if
logging is enabled...

Let's move the barrier in our vhost.c. This
doesn't change any behavior, but makes the code
more readable. It surely looked weird to update
the ring, log it, and then do smp_wmb().

Change-Id: I90827b14292b60bd5641a48d546e7249a0496a4b
Signed-off-by: Dariusz Stojaczyk <dariuszx.stojaczyk@intel.com>
Reviewed-on: https://review.gerrithub.io/398326
Reviewed-by: Pawel Wodkowski <pawelx.wodkowski@intel.com>
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com>
This commit is contained in:
Dariusz Stojaczyk 2018-02-04 14:44:59 +01:00 committed by Jim Harris
parent da78c67091
commit b2847368cc
1 changed files with 3 additions and 2 deletions
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5
lib/vhost/vhost.c
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@ -359,10 +359,11 @@ spdk_vhost_vq_used_ring_enqueue(struct spdk_vhost_dev *vdev, struct spdk_vhost_v
vring->last_used_idx++;
used->ring[last_idx].id = id;
used->ring[last_idx].len = len;
spdk_vhost_log_used_vring_elem(vdev, virtqueue, last_idx);
/* Ensure the used ring is updated before we increment used->idx. */
/* Ensure the used ring is updated before we log it or increment used->idx. */
spdk_smp_wmb();
spdk_vhost_log_used_vring_elem(vdev, virtqueue, last_idx);
* (volatile uint16_t *) &used->idx = vring->last_used_idx;
spdk_vhost_log_used_vring_idx(vdev, virtqueue);