Author: luigi
Date: Mon Dec 5 15:21:21 2011
New Revision: 228280
URL: http://svn.freebsd.org/changeset/base/228280
Log:
revise the implementation of the rings connected to the host stack
Modified:
head/sys/dev/netmap/netmap.c
Modified: head/sys/dev/netmap/netmap.c
==============================================================================
--- head/sys/dev/netmap/netmap.c Mon Dec 5 15:16:47 2011
(r228279)
+++ head/sys/dev/netmap/netmap.c Mon Dec 5 15:21:21 2011
(r228280)
@@ -575,7 +575,13 @@ netmap_mmap(__unused struct cdev *dev, v
/*
- * handler for synchronization of the queues from/to the host
+ * Handlers for synchronization of the queues from/to the host.
+ *
+ * netmap_sync_to_host() passes packets up. We are called from a
+ * system call in user process context, and the only contention
+ * can be among multiple user threads erroneously calling
+ * this routine concurrently. In principle we should not even
+ * need to lock.
*/
static void
netmap_sync_to_host(struct netmap_adapter *na)
@@ -583,15 +589,20 @@ netmap_sync_to_host(struct netmap_adapte
struct netmap_kring *kring = &na->tx_rings[na->num_queues];
struct netmap_ring *ring = kring->ring;
struct mbuf *head = NULL, *tail = NULL, *m;
- u_int n, lim = kring->nkr_num_slots - 1;
+ u_int k, n, lim = kring->nkr_num_slots - 1;
- na->nm_lock(na->ifp->if_softc, NETMAP_CORE_LOCK, 0);
+ k = ring->cur;
+ if (k > lim) {
+ netmap_ring_reinit(kring);
+ return;
+ }
+ // na->nm_lock(na->ifp->if_softc, NETMAP_CORE_LOCK, 0);
/* Take packets from hwcur to cur and pass them up.
* In case of no buffers we give up. At the end of the loop,
* the queue is drained in all cases.
*/
- for (n = kring->nr_hwcur; n != ring->cur;) {
+ for (n = kring->nr_hwcur; n != k;) {
struct netmap_slot *slot = &ring->slot[n];
n = (n == lim) ? 0 : n + 1;
@@ -610,9 +621,9 @@ netmap_sync_to_host(struct netmap_adapte
tail = m;
m->m_nextpkt = NULL;
}
- kring->nr_hwcur = ring->cur;
+ kring->nr_hwcur = k;
kring->nr_hwavail = ring->avail = lim;
- na->nm_lock(na->ifp->if_softc, NETMAP_CORE_UNLOCK, 0);
+ // na->nm_lock(na->ifp->if_softc, NETMAP_CORE_UNLOCK, 0);
/* send packets up, outside the lock */
while ((m = head) != NULL) {
@@ -626,6 +637,10 @@ netmap_sync_to_host(struct netmap_adapte
}
/*
+ * rxsync backend for packets coming from the host stack.
+ * They have been put in the queue by netmap_start() so we
+ * need to protect access to the kring using a lock.
+ *
* This routine also does the selrecord if called from the poll handler
* (we know because td != NULL).
*/
@@ -634,24 +649,29 @@ netmap_sync_from_host(struct netmap_adap
{
struct netmap_kring *kring = &na->rx_rings[na->num_queues];
struct netmap_ring *ring = kring->ring;
- int delta;
+ int error = 1, delta;
+ u_int k = ring->cur, lim = kring->nkr_num_slots;
na->nm_lock(na->ifp->if_softc, NETMAP_CORE_LOCK, 0);
-
- /* skip past packets processed by userspace,
- * and then sync cur/avail with hwcur/hwavail
- */
- delta = ring->cur - kring->nr_hwcur;
+ if (k >= lim) /* bad value */
+ goto done;
+ delta = k - kring->nr_hwcur;
if (delta < 0)
- delta += kring->nkr_num_slots;
+ delta += lim;
kring->nr_hwavail -= delta;
- kring->nr_hwcur = ring->cur;
- ring->avail = kring->nr_hwavail;
- if (ring->avail == 0 && td)
+ if (kring->nr_hwavail < 0) /* error */
+ goto done;
+ kring->nr_hwcur = k;
+ error = 0;
+ k = ring->avail = kring->nr_hwavail;
+ if (k == 0 && td)
selrecord(td, &kring->si);
- if (ring->avail && (netmap_verbose & NM_VERB_HOST))
- D("%d pkts from stack", ring->avail);
+ if (k && (netmap_verbose & NM_VERB_HOST))
+ D("%d pkts from stack", k);
+done:
na->nm_lock(na->ifp->if_softc, NETMAP_CORE_UNLOCK, 0);
+ if (error)
+ netmap_ring_reinit(kring);
}
@@ -1262,25 +1282,24 @@ netmap_detach(struct ifnet *ifp)
/*
- * intercept packets coming from the network stack and present
- * them to netmap as incoming packets on a separate ring.
+ * Intercept packets from the network stack and pass them
+ * to netmap as incoming packets on the 'software' ring.
* We are not locked when called.
*/
int
netmap_start(struct ifnet *ifp, struct mbuf *m)
{
struct netmap_adapter *na = NA(ifp);
- u_int i, len, n = na->num_queues;
- int error = EBUSY;
- struct netmap_kring *kring = &na->rx_rings[n];
+ struct netmap_kring *kring = &na->rx_rings[na->num_queues];
+ u_int i, len = m->m_pkthdr.len;
+ int error = EBUSY, lim = kring->nkr_num_slots - 1;
struct netmap_slot *slot;
- len = m->m_pkthdr.len;
if (netmap_verbose & NM_VERB_HOST)
D("%s packet %d len %d from the stack", ifp->if_xname,
kring->nr_hwcur + kring->nr_hwavail, len);
na->nm_lock(ifp->if_softc, NETMAP_CORE_LOCK, 0);
- if (kring->nr_hwavail >= (int)kring->nkr_num_slots - 1) {
+ if (kring->nr_hwavail >= lim) {
D("stack ring %s full\n", ifp->if_xname);
goto done; /* no space */
}
@@ -1291,8 +1310,8 @@ netmap_start(struct ifnet *ifp, struct m
/* compute the insert position */
i = kring->nr_hwcur + kring->nr_hwavail;
- if (i >= kring->nkr_num_slots)
- i -= kring->nkr_num_slots;
+ if (i > lim)
+ i -= lim + 1;
slot = &kring->ring->slot[i];
m_copydata(m, 0, len, NMB(slot));
slot->len = len;
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