Author: mav
Date: Wed May 6 18:04:31 2015
New Revision: 282563
URL: https://svnweb.freebsd.org/changeset/base/282563
Log:
Add memory barrier to r281764.
While race at this point may cause only a single packet delay and so was
not really reproduced, it is better to not have it at all.
MFC after: 1 week
Modified:
head/usr.sbin/bhyve/pci_virtio_net.c
Modified: head/usr.sbin/bhyve/pci_virtio_net.c
==============================================================================
--- head/usr.sbin/bhyve/pci_virtio_net.c Wed May 6 17:44:42 2015
(r282562)
+++ head/usr.sbin/bhyve/pci_virtio_net.c Wed May 6 18:04:31 2015
(r282563)
@@ -34,6 +34,7 @@ __FBSDID("$FreeBSD$");
#include <sys/select.h>
#include <sys/uio.h>
#include <sys/ioctl.h>
+#include <machine/atomic.h>
#include <net/ethernet.h>
#include <errno.h>
@@ -453,7 +454,7 @@ pci_vtnet_tx_thread(void *param)
{
struct pci_vtnet_softc *sc = param;
struct vqueue_info *vq;
- int have_work, error;
+ int error;
vq = &sc->vsc_queues[VTNET_TXQ];
@@ -467,20 +468,16 @@ pci_vtnet_tx_thread(void *param)
for (;;) {
/* note - tx mutex is locked here */
- do {
+ while (sc->resetting || !vq_has_descs(vq)) {
vq->vq_used->vu_flags &= ~VRING_USED_F_NO_NOTIFY;
- if (sc->resetting)
- have_work = 0;
- else
- have_work = vq_has_descs(vq);
-
- if (!have_work) {
- sc->tx_in_progress = 0;
- error = pthread_cond_wait(&sc->tx_cond,
- &sc->tx_mtx);
- assert(error == 0);
- }
- } while (!have_work);
+ mb();
+ if (!sc->resetting && vq_has_descs(vq))
+ break;
+
+ sc->tx_in_progress = 0;
+ error = pthread_cond_wait(&sc->tx_cond, &sc->tx_mtx);
+ assert(error == 0);
+ }
vq->vq_used->vu_flags |= VRING_USED_F_NO_NOTIFY;
sc->tx_in_progress = 1;
pthread_mutex_unlock(&sc->tx_mtx);
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