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Subject: [ Patch ]: Fix loopback communication latency bug
From: yangyi <yang.yi@bmrtech.com>
Reply-To: yang.yi@bmrtech.com
To: Ingo Molnar <mingo@elte.hu>
Cc: "Rt-Dev@Mvista. Com" <rt-dev@mvista.com>,
       LKML <linux-kernel@vger.kernel.org>
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Organization: bmrtech
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Date: Tue, 19 Apr 2005 16:03:10 +0800
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Hi, Ingo

For the option PREEMPT_RT, local communication latency is very very big,
it is about 30 to 50 times as big as the option PREEMPT_NONE as far as
local ping latency is concerned. Obviously, this should be fixed ASAP.

This patch fixes this bug by changing netif_rx to netif_rx_ni in
loopback device driver.

--- linux-2.6.10-orig/drivers/net/loopback.c    2005-04-19
15:12:34.000000000 +0800
+++ linux-2.6.10/drivers/net/loopback.c 2005-04-19 15:13:28.000000000
+0800
@@ -153,7 +153,7 @@ static int loopback_xmit(struct sk_buff
        lb_stats->tx_packets++;
        put_cpu();

-       netif_rx(skb);
+       netif_rx_ni(skb);

        return(0);
 }