[PATCH] sfc: Call netif_napi_add() before registering our interrupt handler

[PATCH] sfc: Call netif_napi_add() before registering our interrupt handler

[Ben Hutchings]

If we use a shared legacy IRQ then our interrupt handler may be called
as soon as it is registered even though IRQs are disabled on the NIC.
Now that the legacy interrupt handler also checks for event delivery,
it may decide to schedule polling in this case.  Ensure that the NAPI
context is valid but disabled at this point.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
---
Please apply this to net-2.6; the bug it fixes is much easier to hit
following commit a9de9a74c69f75e9456cd6b45ecab44ff4c81d04

Ben.

 drivers/net/sfc/efx.c |    7 +++----
 1 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/net/sfc/efx.c b/drivers/net/sfc/efx.c
index 00c23b1..dee23b1 100644
--- a/drivers/net/sfc/efx.c
+++ b/drivers/net/sfc/efx.c
@@ -448,6 +448,9 @@ static void efx_init_channels(struct efx_nic *efx)
 
 		WARN_ON(channel->rx_pkt != NULL);
 		efx_rx_strategy(channel);
+
+		netif_napi_add(channel->napi_dev, &channel->napi_str,
+			       efx_poll, napi_weight);
 	}
 }
 
@@ -462,10 +465,6 @@ static void efx_start_channel(struct efx_channel *channel)
 
 	EFX_LOG(channel->efx, "starting chan %d\n", channel->channel);
 
-	if (!(channel->efx->net_dev->flags & IFF_UP))
-		netif_napi_add(channel->napi_dev, &channel->napi_str,
-			       efx_poll, napi_weight);
-
 	/* The interrupt handler for this channel may set work_pending
 	 * as soon as we enable it.  Make sure it's cleared before
 	 * then.  Similarly, make sure it sees the enabled flag set. */

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

Re: [PATCH] sfc: Call netif_napi_add() before registering our interrupt handler

[David Miller]

From: Ben Hutchings <bhutchings@solarflare.com>
Date: Tue, 31 Mar 2009 20:07:44 +0100

> If we use a shared legacy IRQ then our interrupt handler may be called
> as soon as it is registered even though IRQs are disabled on the NIC.
> Now that the legacy interrupt handler also checks for event delivery,
> it may decide to schedule polling in this case.  Ensure that the NAPI
> context is valid but disabled at this point.
> 
> Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

Applied, thanks.