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bnx2x: Tx barriers and locks

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[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: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Vladislav Zolotarov <vladz@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Vladislav Zolotarov 2010-02-28 00:12:02 +00:00 committed by David S. Miller
parent 76dadd76c2
commit c16cc0b464
1 changed files with 22 additions and 9 deletions
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31
drivers/net/bnx2x_main.c
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@ -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;
/* 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_wmb();
/* 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.
/* 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
*/
smp_mb();
__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;
}