prevent rb ether from locking up due to queue full conditions

Reference: /n/atom/patch/applied2013/rbetherhangup
Date: Sat Sep 21 21:08:39 CES 2013
Signed-off-by: quanstro@quanstro.net

--- /sys/src/9/rb/devether.c	Sat Sep 21 21:08:39 2013
+++ /sys/src/9/rb/devether.c	Sat Sep 21 21:08:39 2013
@@ -231,7 +231,7 @@
 	Dmatxunderrun	= 1 << 1,
 	Dmatxpktsent	= 1 << 0,
 	/* we don't really need most tx interrupts */
-	Dmaall		= Dmarxbuserr | Dmarxovflo | Dmarxpktrcvd | Dmatxbuserr,
+	Dmaall		= Dmarxbuserr | /* Dmarxovflo |*/ Dmarxpktrcvd | Dmatxbuserr,
 
 	Spictlremapdisable	= 1 << 6,
 	Spictlclkdividermask	= MASK(6),
@@ -702,7 +702,7 @@
 	Desc *rd;
 
 	if (ctlr->rd[i] != nil)
-		return;
+		panic("rxnewbuf: overflow"); //return;
 	ctlr->rd[i] = bp = athrballoc();
 	if(bp == nil)
 		panic("#l%d: can't allocate receive buffer",
@@ -741,12 +741,12 @@
 	arge = ctlr->regs;
 	ilock(ctlr);
 	sts = arge->dmaintrsts;
-	if (sts & Dmarxpktrcvd) {
+	if (sts & (Dmarxpktrcvd | Dmarxovflo)) {
 		arge->dmaintr &= ~Dmarxpktrcvd;
 		ctlr->pktstoread = 1;
 		wakeup(&ctlr->rrendez);
 		ctlr->rintr++;
-		sts &= ~Dmarxpktrcvd;
+		sts &= ~(Dmarxpktrcvd | Dmarxovflo);
 	}
 	if (sts & (Dmatxpktsent | Dmatxunderrun)) {
 		arge->dmaintr &= ~(Dmatxpktsent | Dmatxunderrun);
@@ -755,6 +755,7 @@
 		ctlr->tintr++;
 		sts &= ~(Dmatxpktsent | Dmatxunderrun);
 	}
+
 	iunlock(ctlr);
 	if (sts)
 		iprint("#l%d: sts %#ux\n", ether->ctlrno, sts);
@@ -771,7 +772,7 @@
 static void
 rproc(void* arg)
 {
-	uint rdh, sz;
+	uint rdh, sz, n;
 	Arge *arge;
 	Block *bp;
 	Ctlr *ctlr;
@@ -782,9 +783,12 @@
 	ctlr = edev->ctlr;
 	arge = ctlr->regs;
 	for(;;){
+		rxreclaim(edev->ctlr);
+
 		/* wait for next interrupt */
 		ilock(ctlr);
 		arge->dmaintr |= Dmarxpktrcvd;
+arge->rxctl = Dmarxctlen;
 		iunlock(ctlr);
 
 		sleep(&ctlr->rrendez, pktstoread, ctlr);
@@ -792,6 +796,7 @@
 
 		rxreclaim(ctlr);
 		rdh = ctlr->rdh;
+		n = 0;
 		for (rd = &ctlr->rdba[rdh]; !(rd->ctl & Descempty);
 		     rd = &ctlr->rdba[rdh]){
 			bp = ctlr->rd[rdh];
@@ -802,17 +807,17 @@
 			sz = DMASIZE(rd->ctl) - 4;
 			assert(sz > 0 && sz <= Rbsz);
 			bp->wp = bp->rp + sz;
-			bp = etheriq(edev, bp, 1);
-			assert(bp == nil);		/* Block was consumed */
+			etheriq(edev, bp, 1);
 
 			arge->rxsts = Rxpktrcvd;
 
 			ctlr->nrdfree--;
 			rdh = NEXT(rdh, Nrd);
-			if(ctlr->nrdfree < Nrd/2) {
+			if(++n >= 8) {
 				/* rxreclaim reads ctlr->rdh */
 				ctlr->rdh = rdh;
 				rxreclaim(edev->ctlr);
+				n = 0;
 			}
 		}
 		ctlr->rdh = rdh;
@@ -842,12 +847,12 @@
 	ctlr = edev->ctlr;
 	arge = ctlr->regs;
 	for(;;){
+		txreclaim(ctlr);
+
 		/* wait for next free buffer and output queue block */
 		sleep(&ctlr->trendez, pktstosend, edev);
 		ctlr->pktstosend = 0;
 
-		txreclaim(ctlr);
-
 		/* copy as much of my output q as possible into output ring */
 		added = 0;
 		tdt = ctlr->tdt;
@@ -890,7 +895,6 @@
 		else if (ctlr->ntq > 0)
 			arge->dmaintr |= Dmatxunderrun;
 		iunlock(ctlr);
-		txreclaim(ctlr);
 	}
 }