netdev - [PATCH] e1000e: stop unnecessary polling when using msi-x

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Message-ID: <20090618215737.GF8515@gospo.rdu.redhat.com>
Date:	Thu, 18 Jun 2009 17:57:37 -0400
From:	Andy Gospodarek <andy@...yhouse.net>
To:	netdev@...r.kernel.org, bruce.w.allan@...el.com,
	jeffrey.t.kirsher@...el.com, jesse.brandeburg@...el.com,
	alexander.h.duyck@...el.com
Cc:	stable@...nel.org
Subject: [PATCH] e1000e: stop unnecessary polling when using msi-x


The last hunk of this commit:

    commit 12d04a3c12b420f23398b4d650127642469a60a6
    Author: Alexander Duyck <alexander.h.duyck@...el.com>
    Date:   Wed Mar 25 22:05:03 2009 +0000

        e1000e: commonize tx cleanup routine to match e1000 & igb

changed the logic for determining if we should call napi_complete or
not at then end of a napi poll.

If the NIC is using MSI-X with no work to do in ->poll, net_rx_action
can just spin indefinitely on older kernels and for 2 jiffies on newer
kernels since napi_complete is never called and budget isn't
decremented.

Discovered and verified while testing driver backport to an older
kernel.

Signed-off-by: Andy Gospodarek <andy@...yhouse.net>

---

 netdev.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/e1000e/netdev.c b/drivers/net/e1000e/netdev.c
index 677f604..679885a 100644
--- a/drivers/net/e1000e/netdev.c
+++ b/drivers/net/e1000e/netdev.c
@@ -1997,7 +1997,7 @@ static int e1000_clean(struct napi_struct *napi, int budget)
 	struct e1000_adapter *adapter = container_of(napi, struct e1000_adapter, napi);
 	struct e1000_hw *hw = &adapter->hw;
 	struct net_device *poll_dev = adapter->netdev;
-	int tx_cleaned = 0, work_done = 0;
+	int tx_cleaned = 1, work_done = 0;
 
 	adapter = netdev_priv(poll_dev);


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