Date: Mon, 5 Dec 2011 15:21:22 +0000 (UTC) From: Luigi Rizzo <luigi@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r228280 - head/sys/dev/netmap Message-ID: <201112051521.pB5FLM2e042646@svn.freebsd.org>
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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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