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Commit c16cc0b4 authored by Vladislav Zolotarov's avatar Vladislav Zolotarov Committed by David S. Miller
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bnx2x: Tx barriers and locks 



[Resending with the proper subject. Sorry for the mess. ]

This patch is based on the RFC of Stanislaw Gruszka.

More specifically it fixes two possible races:
- One, described by Stanislaw, may lead to permanent disabling of the Tx
queue.
This is fixed by adding the smp_wmb() to propagate the BD consumer
change towards the memory.
- Second may lead to bnx2x_start_xmit() returning NETDEV_TX_BUSY.
This is fixed by taking a tx_lock() before rechecking the number of
available Tx BDs.

thanks,
vlad

Signed-off-by: default avatarStanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: default avatarVladislav Zolotarov <vladz@broadcom.com>
Signed-off-by: default avatarEilon Greenstein <eilong@broadcom.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 76dadd76

drivers/net/bnx2x_main.c

+22 −9
Original line number Diff line number Diff line
@@ -57,8 +57,8 @@ 
#include "bnx2x_init_ops.h"

#include "bnx2x_dump.h"



#define DRV_MODULE_VERSION	"1.52.1-6"

#define DRV_MODULE_RELDATE	"2010/02/16"

#define DRV_MODULE_VERSION	"1.52.1-7"

#define DRV_MODULE_RELDATE	"2010/02/28"

#define BNX2X_BC_VER		0x040200



#include <linux/firmware.h>
@@ -957,21 +957,34 @@ static int bnx2x_tx_int(struct bnx2x_fastpath *fp) 
	fp->tx_pkt_cons = sw_cons;

	fp->tx_bd_cons = bd_cons;



	/* TBD need a thresh? */

	if (unlikely(netif_tx_queue_stopped(txq))) {



	/* Need to make the tx_bd_cons update visible to start_xmit()

	 * before checking for netif_tx_queue_stopped().  Without the

	 * memory barrier, there is a small possibility that

	 * start_xmit() will miss it and cause the queue to be stopped

	 * forever.

	 */

		smp_mb();

	smp_wmb();



	/* TBD need a thresh? */

	if (unlikely(netif_tx_queue_stopped(txq))) {

		/* Taking tx_lock() is needed to prevent reenabling the queue

		 * while it's empty. This could have happen if rx_action() gets

		 * suspended in bnx2x_tx_int() after the condition before

		 * netif_tx_wake_queue(), while tx_action (bnx2x_start_xmit()):

		 *

		 * stops the queue->sees fresh tx_bd_cons->releases the queue->

		 * sends some packets consuming the whole queue again->

		 * stops the queue

		 */



		__netif_tx_lock(txq, smp_processor_id());



		if ((netif_tx_queue_stopped(txq)) &&

		    (bp->state == BNX2X_STATE_OPEN) &&

		    (bnx2x_tx_avail(fp) >= MAX_SKB_FRAGS + 3))

			netif_tx_wake_queue(txq);



		__netif_tx_unlock(txq);

	}

	return 0;

}