[PATCH 2.6.18 1/3] tg3: Remove unnecessary tx_lock

[PATCH 2.6.18 1/3] tg3: Remove unnecessary tx_lock

[Michael Chan]

Remove tx_lock where it is unnecessary. tg3 runs lockless and so it
requires interrupts to be disabled and sync'ed, netif_queue and NAPI
poll to be stopped before the device can be reconfigured. After
stopping everything, it is no longer necessary to get the tx_lock.

Signed-off-by: Michael Chan <mchan@broadcom.com>


diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c
index f2382aa..4cda2af 100644
--- a/drivers/net/tg3.c
+++ b/drivers/net/tg3.c
@@ -2984,9 +2984,7 @@ static void tg3_tx_recover(struct tg3 *t
 	       "and include system chipset information.\n", tp->dev->name);
 
 	spin_lock(&tp->lock);
-	spin_lock(&tp->tx_lock);
 	tp->tg3_flags |= TG3_FLAG_TX_RECOVERY_PENDING;
-	spin_unlock(&tp->tx_lock);
 	spin_unlock(&tp->lock);
 }
 
@@ -3429,12 +3427,10 @@ static inline void tg3_full_lock(struct 
 	if (irq_sync)
 		tg3_irq_quiesce(tp);
 	spin_lock_bh(&tp->lock);
-	spin_lock(&tp->tx_lock);
 }
 
 static inline void tg3_full_unlock(struct tg3 *tp)
 {
-	spin_unlock(&tp->tx_lock);
 	spin_unlock_bh(&tp->lock);
 }
 

Re: [PATCH 2.6.18 1/3] tg3: Remove unnecessary tx_lock

[Herbert Xu]

On Mon, Jun 05, 2006 at 12:47:23PM -0700, Michael Chan wrote:
> Remove tx_lock where it is unnecessary. tg3 runs lockless and so it
> requires interrupts to be disabled and sync'ed, netif_queue and NAPI
> poll to be stopped before the device can be reconfigured. After
> stopping everything, it is no longer necessary to get the tx_lock.

The paths where full lock is preceded by netif_tx_disable are obviously
safe (well, once you take off the LLTX flag anyway).  However, there are
paths that don't do netif_tx_disable (e.g., tg3_set_rx_mode), are they
safe as well?

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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Re: [PATCH 2.6.18 1/3] tg3: Remove unnecessary tx_lock

[Michael Chan]

Herbert Xu wrote:

> The paths where full lock is preceded by netif_tx_disable are 
> obviously
> safe (well, once you take off the LLTX flag anyway).  
> However, there are
> paths that don't do netif_tx_disable (e.g., tg3_set_rx_mode), are they
> safe as well?
> 

In places where we don't call tg3_netif_stop() before tg3_full_lock(),
we are typically doing one of the following:

- changing tg3_flags or tg3_flags2
- reprogramming MAC address
- reprogramming interrupt coalescing values
- reprogramming the PHY
- setting the rx mode

The TX code does not do any of these so it is safe.

tg3_set_rx_mode() is actually called with xmit_lock held through
dev->set_multicast_list(). Or it is called after tg3_netif_stop() in
the VLAN registration calls (in my patch #3).

Re: [PATCH 2.6.18 1/3] tg3: Remove unnecessary tx_lock

[Herbert Xu]

On Mon, Jun 05, 2006 at 10:10:56PM -0700, Michael Chan wrote:
>
> In places where we don't call tg3_netif_stop() before tg3_full_lock(),
> we are typically doing one of the following:
> 
> - changing tg3_flags or tg3_flags2
> - reprogramming MAC address
> - reprogramming interrupt coalescing values
> - reprogramming the PHY
> - setting the rx mode

OK, thanks for checking.
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH 2.6.18 1/3] tg3: Remove unnecessary tx_lock

[David Miller]

From: "Michael Chan" <mchan@broadcom.com>
Date: Mon, 05 Jun 2006 12:47:23 -0700

> Remove tx_lock where it is unnecessary. tg3 runs lockless and so it
> requires interrupts to be disabled and sync'ed, netif_queue and NAPI
> poll to be stopped before the device can be reconfigured. After
> stopping everything, it is no longer necessary to get the tx_lock.
> 
> Signed-off-by: Michael Chan <mchan@broadcom.com>

Applied, thanks.