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Commit 7ae52890 authored by Michael Chan's avatar Michael Chan Committed by David S. Miller
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tg3: Fix RSS ring refill race condition 



The RSS feature in tg3 hardware has only one rx producer ring for all
RSS rings.  NAPI vector 1 is special and handles the refilling of the
rx producer ring on behalf of all RSS rings.  There is a race condition
between these RSS NAPIs and the NAPI[1].  If NAPI[1] finishes checking
for refill and then another RSS ring empties the rx producer ring
before NAPI[1] exits NAPI, the chip will be completely out of SKBs in
the rx producer ring.

We fix this by adding a flag tp->rx_refill and rely on napi_schedule()/
napi_complete() to help synchronize it to close the race condition.

Update driver version to 3.123.

Signed-off-by: default avatarMichael Chan <mchan@broadcom.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 5676cc7b

drivers/net/ethernet/broadcom/tg3.c

+22 −3
Original line number Diff line number Diff line
@@ -89,10 +89,10 @@ static inline void _tg3_flag_clear(enum TG3_FLAGS flag, unsigned long *bits) 


#define DRV_MODULE_NAME		"tg3"

#define TG3_MAJ_NUM			3

#define TG3_MIN_NUM			122

#define TG3_MIN_NUM			123

#define DRV_MODULE_VERSION	\

	__stringify(TG3_MAJ_NUM) "." __stringify(TG3_MIN_NUM)

#define DRV_MODULE_RELDATE	"December 7, 2011"

#define DRV_MODULE_RELDATE	"March 21, 2012"



#define RESET_KIND_SHUTDOWN	0

#define RESET_KIND_INIT		1
@@ -5953,9 +5953,11 @@ next_pkt_nopost: 
		tpr->rx_std_prod_idx = std_prod_idx & tp->rx_std_ring_mask;

		tpr->rx_jmb_prod_idx = jmb_prod_idx & tp->rx_jmb_ring_mask;



		if (tnapi != &tp->napi[1])

		if (tnapi != &tp->napi[1]) {

			tp->rx_refill = true;

			napi_schedule(&tp->napi[1].napi);

		}

	}



	return received;

}
@@ -6134,6 +6136,7 @@ static int tg3_poll_work(struct tg3_napi *tnapi, int work_done, int budget) 
		u32 std_prod_idx = dpr->rx_std_prod_idx;

		u32 jmb_prod_idx = dpr->rx_jmb_prod_idx;



		tp->rx_refill = false;

		for (i = 1; i < tp->irq_cnt; i++)

			err |= tg3_rx_prodring_xfer(tp, dpr,

						    &tp->napi[i].prodring);
@@ -6197,9 +6200,25 @@ static int tg3_poll_msix(struct napi_struct *napi, int budget) 
		/* check for RX/TX work to do */

		if (likely(sblk->idx[0].tx_consumer == tnapi->tx_cons &&

			   *(tnapi->rx_rcb_prod_idx) == tnapi->rx_rcb_ptr)) {



			/* This test here is not race free, but will reduce

			 * the number of interrupts by looping again.

			 */

			if (tnapi == &tp->napi[1] && tp->rx_refill)

				continue;



			napi_complete(napi);

			/* Reenable interrupts. */

			tw32_mailbox(tnapi->int_mbox, tnapi->last_tag << 24);



			/* This test here is synchronized by napi_schedule()

			 * and napi_complete() to close the race condition.

			 */

			if (unlikely(tnapi == &tp->napi[1] && tp->rx_refill)) {

				tw32(HOSTCC_MODE, tp->coalesce_mode |

						  HOSTCC_MODE_ENABLE |

						  tnapi->coal_now);

			}

			mmiowb();

			break;

		}

drivers/net/ethernet/broadcom/tg3.h

+1 −0
Original line number Diff line number Diff line
@@ -3007,6 +3007,7 @@ struct tg3 { 
	u32				rx_std_max_post;

	u32				rx_offset;

	u32				rx_pkt_map_sz;

	bool				rx_refill;





	/* begin "everything else" cacheline(s) section */