Netmap分析（六）

netmap.c

NIOCTXSYNC和NIOCRXSYNC
这两个使用相同的代码,同步ring

case NIOCTXSYNC:
	case NIOCRXSYNC:
		nifp = priv->np_nifp;

		if (nifp == NULL) {
			error = ENXIO;
			break;
		}
		mb(); /* make sure following reads are not from cache */

		na = priv->np_na;      /* we have a reference */

		if (na == NULL) {
			D("Internal error: nifp != NULL && na == NULL");
			error = ENXIO;
			break;
		}

		t = (cmd == NIOCTXSYNC ? NR_TX : NR_RX);
//得到tx/rx ring地址
		krings = NMR(na, t);
		qfirst = priv->np_qfirst[t];
		qlast = priv->np_qlast[t];

		for (i = qfirst; i < qlast; i++) {
			struct netmap_kring *kring = krings + i;
			struct netmap_ring *ring = kring->ring;

			if (unlikely(nm_kr_tryget(kring, 1, &error))) {
				error = (error ? EIO : 0);
				continue;
			}

			if (cmd == NIOCTXSYNC) {
				if (netmap_verbose & NM_VERB_TXSYNC)
					D("pre txsync ring %d cur %d hwcur %d",
					    i, ring->cur,
					    kring->nr_hwcur);
				if (nm_txsync_prologue(kring, ring) >= kring->nkr_num_slots) {
					netmap_ring_reinit(kring);
				} else if (kring->nm_sync(kring, NAF_FORCE_RECLAIM) == 0) {
					nm_sync_finalize(kring);
				}
				if (netmap_verbose & NM_VERB_TXSYNC)
					D("post txsync ring %d cur %d hwcur %d",
					    i, ring->cur,
					    kring->nr_hwcur);
			} else {
				if (nm_rxsync_prologue(kring, ring) >= kring->nkr_num_slots) {
					netmap_ring_reinit(kring);
				} else if (kring->nm_sync(kring, NAF_FORCE_READ) == 0) {
					nm_sync_finalize(kring);
				}
				microtime(&ring->ts);
			}
			nm_kr_put(kring);
		}

		break;