From 2f8af120a159a843948749ea88bcacda9779b132 Mon Sep 17 00:00:00 2001 From: Michael Chan Date: Tue, 15 Aug 2006 01:39:10 -0700 Subject: [BNX2]: Fix tx race condition. Fix a subtle race condition between bnx2_start_xmit() and bnx2_tx_int() similar to the one in tg3 discovered by Herbert Xu: CPU0 CPU1 bnx2_start_xmit() if (tx_ring_full) { tx_lock bnx2_tx() if (!netif_queue_stopped) netif_stop_queue() if (!tx_ring_full) update_tx_ring netif_wake_queue() tx_unlock } Even though tx_ring is updated before the if statement in bnx2_tx_int() in program order, it can be re-ordered by the CPU as shown above. This scenario can cause the tx queue to be stopped forever if bnx2_tx_int() has just freed up the entire tx_ring. The possibility of this happening should be very rare though. The following changes are made, very much identical to the tg3 fix: 1. Add memory barrier to fix the above race condition. 2. Eliminate the private tx_lock altogether and rely solely on netif_tx_lock. This eliminates one spinlock in bnx2_start_xmit() when the ring is full. 3. Because of 2, use netif_tx_lock in bnx2_tx_int() before calling netif_wake_queue(). 4. Add memory barrier to bnx2_tx_avail(). 5. Add bp->tx_wake_thresh which is set to half the tx ring size. 6. Check for the full wake queue condition before getting netif_tx_lock in tg3_tx(). This reduces the number of unnecessary spinlocks when the tx ring is full in a steady-state condition. Signed-off-by: Michael Chan Signed-off-by: David S. Miller --- drivers/net/bnx2.h | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) (limited to 'drivers/net/bnx2.h') diff --git a/drivers/net/bnx2.h b/drivers/net/bnx2.h index 658c5ee95c7..fe804763c60 100644 --- a/drivers/net/bnx2.h +++ b/drivers/net/bnx2.h @@ -3890,10 +3890,6 @@ struct bnx2 { u32 tx_prod_bseq __attribute__((aligned(L1_CACHE_BYTES))); u16 tx_prod; - struct tx_bd *tx_desc_ring; - struct sw_bd *tx_buf_ring; - int tx_ring_size; - u16 tx_cons __attribute__((aligned(L1_CACHE_BYTES))); u16 hw_tx_cons; @@ -3916,9 +3912,11 @@ struct bnx2 { struct sw_bd *rx_buf_ring; struct rx_bd *rx_desc_ring[MAX_RX_RINGS]; - /* Only used to synchronize netif_stop_queue/wake_queue when tx */ - /* ring is full */ - spinlock_t tx_lock; + /* TX constants */ + struct tx_bd *tx_desc_ring; + struct sw_bd *tx_buf_ring; + int tx_ring_size; + u32 tx_wake_thresh; /* End of fields used in the performance code paths. */ -- cgit v1.2.3