netdev - __kfree_skb eventually calls kfree_skb violating dropwatch assumption

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Message-ID: <27F465BDABE6954AABB2A4E3599BDAC702AD1DC3AB@sausexmbp02.amd.com>
Date:	Wed, 12 Oct 2011 21:25:10 -0500
From:	"Suresh, Charles" <Charles.Suresh@....com>
To:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:	"nhorman@...hat.com" <nhorman@...hat.com>
Subject: __kfree_skb eventually calls kfree_skb violating dropwatch
 assumption

kfree_skb can be called from __kfree_skb through the following call chain :

kfree_skb  <- skb_drop_list <- skb_drop_fraglist <- skb_release_data <-  skb_release_all <- __kfree_skb (on the 2.38.4 kernel).

This violates the assumption in the dropwatch tool that discarded packets go through the kfree_skb path and all others must go through the consume_skb path (thus resulting in the over-counting of discarded packets in dropwatch).

Neil Horman the author of dropwatch suggested that this could be fixed by skb_drop_list calling consume_skb instead of kfree_skb.

Charles

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