From: Al Viro <viro@ftp.linux.org.uk>
To: netdev@vger.kernel.org
Cc: christopher.leech@intel.com
Subject: NET_DMA: where do we ever call dma_skb_copy_datagram_iovec() with NULL pinned_list?
Date: Sat, 21 Jul 2007 04:48:29 +0100 [thread overview]
Message-ID: <20070721034829.GL21668@ftp.linux.org.uk> (raw)
AFAICS, all callers of dma_skb_copy_datagram_iovec()
are either
* recursive for fragments, pass pinned_list unchanged or
* called from tcp, with pinned_list coming from
tp->ucopy.pinned_list and only when tp->ucopy.dma_chan is non-NULL.
Now, all non-NULL assignments to ->dma_chan have the same form:
if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list)
tp->ucopy.dma_chan = get_softnet_dma();
IOW, if ->ucopy.pinned_list stays NULL, ->ucopy.dma_chan will do the same.
Moreover, any place that resets ->ucopy.pinned_list will also reset
->ucopy.dma_chan.
IOW, we can't ever get non-NULL tp->ucopy.dma_chan while tp->ucopy.pinned_list
is NULL. So how can we ever get to the dma_memcpy_to_kernel_iovec()?
next reply other threads:[~2007-07-21 3:48 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-07-21 3:48 Al Viro [this message]
2007-07-24 17:24 ` NET_DMA: where do we ever call dma_skb_copy_datagram_iovec() with NULL pinned_list? Andrew Grover
2007-07-24 18:14 ` Nelson, Shannon
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