From c8ea5a22bd3b27d68ec2f95483ce8bfe7f114933 Mon Sep 17 00:00:00 2001 From: Soren Brinkmann Date: Sun, 4 May 2014 15:43:02 -0700 Subject: [PATCH] net: macb: Fix race between HW and driver Under "heavy" RX load, the driver cannot handle the descriptors fast enough. In detail, when a descriptor is consumed, its used flag is cleared and once the RX budget is consumed all descriptors with a cleared used flag are prepared to receive more data. Under load though, the HW may constantly receive more data and use those descriptors with a cleared used flag before they are actually prepared for next usage. The head and tail pointers into the RX-ring should always be valid and we can omit clearing and checking of the used flag. Signed-off-by: Soren Brinkmann Signed-off-by: David S. Miller --- drivers/net/ethernet/cadence/macb.c | 10 ---------- 1 file changed, 10 deletions(-) diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c index 3e13aa31548a..e9daa072ebb4 100644 --- a/drivers/net/ethernet/cadence/macb.c +++ b/drivers/net/ethernet/cadence/macb.c @@ -599,25 +599,16 @@ static void gem_rx_refill(struct macb *bp) { unsigned int entry; struct sk_buff *skb; - struct macb_dma_desc *desc; dma_addr_t paddr; while (CIRC_SPACE(bp->rx_prepared_head, bp->rx_tail, RX_RING_SIZE) > 0) { - u32 addr, ctrl; - entry = macb_rx_ring_wrap(bp->rx_prepared_head); - desc = &bp->rx_ring[entry]; /* Make hw descriptor updates visible to CPU */ rmb(); - addr = desc->addr; - ctrl = desc->ctrl; bp->rx_prepared_head++; - if ((addr & MACB_BIT(RX_USED))) - continue; - if (bp->rx_skbuff[entry] == NULL) { /* allocate sk_buff for this free entry in ring */ skb = netdev_alloc_skb(bp->dev, bp->rx_buffer_size); @@ -698,7 +689,6 @@ static int gem_rx(struct macb *bp, int budget) if (!(addr & MACB_BIT(RX_USED))) break; - desc->addr &= ~MACB_BIT(RX_USED); bp->rx_tail++; count++; -- 2.11.0