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Date: Sun, 23 Sep 2007 12:55:19 -0500 From: Steve Wise <swise@...ngridcomputing.com> To: Evgeniy Polyakov <johnpol@....mipt.ru> CC: netdev@...r.kernel.org Subject: Re: pktgen question Evgeniy Polyakov wrote: > Hi Steve. > > On Sun, Sep 23, 2007 at 11:12:12AM -0500, Steve Wise (swise@...ngridcomputing.com) wrote: >> The pktgen module provides a way to "clone" the skb its using for >> transmission, and allows passing N clones of the originally created skb >> to the driver under test. However, it doesn't really use skb_clone(), >> but rather it just bumps the skb->users count for each "clone" and >> passes the same skb ptr to the driver. >> >> Q: Is that a valid use of skb->users or should pktgen really be cloning >> the skbuff? > > It's a hack, but since skb is owned by pktgen only (no copies in some > outside queues or some other access) it is allowed just to bump reference > counter (i.e. 'share' skb in usual notation). > Its a hack that breaks cxgb3 because cxgb3 uses the skb->cb area for each skb passed down. So cxgb3 is at fault then? IE a driver cannot use the skb->cb field if the users count is > 1? Or maybe a driver can _never_ use the cb field? Steve. - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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