From 1b2a720506ccf7c30baaeda5d990c29b31e21726 Mon Sep 17 00:00:00 2001 From: Michael Chan Date: Mon, 7 Aug 2006 21:46:02 -0700 Subject: [TG3]: Fix tx race condition Fix a subtle race condition between tg3_start_xmit() and tg3_tx() discovered by Herbert Xu : CPU0 CPU1 tg3_start_xmit() if (tx_ring_full) { tx_lock tg3_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 tg3_tx() 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 tg3_tx() has just freed up the entire tx_ring. The possibility of this happening should be very rare though. The following changes are made: 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 tg3_start_xmit() when the ring is full. 3. Because of 2, use netif_tx_lock in tg3_tx() before calling netif_wake_queue(). 4. Change TX_BUFFS_AVAIL to an inline function with a memory barrier. Herbert and David suggested using the memory barrier instead of volatile. 5. 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. 6. Update version to 3.65. Signed-off-by: Michael Chan Acked-by: Herbert Xu Signed-off-by: David S. Miller --- drivers/net/tg3.h | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) (limited to 'drivers/net/tg3.h') diff --git a/drivers/net/tg3.h b/drivers/net/tg3.h index ba2c98711c8..3ecf356cfb0 100644 --- a/drivers/net/tg3.h +++ b/drivers/net/tg3.h @@ -2079,9 +2079,9 @@ struct tg3 { * lock: Held during reset, PHY access, timer, and when * updating tg3_flags and tg3_flags2. * - * tx_lock: Held during tg3_start_xmit and tg3_tx only - * when calling netif_[start|stop]_queue. - * tg3_start_xmit is protected by netif_tx_lock. + * netif_tx_lock: Held during tg3_start_xmit. tg3_tx holds + * netif_tx_lock when it needs to call + * netif_wake_queue. * * Both of these locks are to be held with BH safety. * @@ -2118,8 +2118,6 @@ struct tg3 { u32 tx_cons; u32 tx_pending; - spinlock_t tx_lock; - struct tg3_tx_buffer_desc *tx_ring; struct tx_ring_info *tx_buffers; dma_addr_t tx_desc_mapping; -- cgit v1.2.3