This is a note to let you know that I've just added the patch titled
tcp: flush DMA queue before sk_wait_data if rcv_wnd is zero
to the 3.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tcp-flush-dma-queue-before-sk_wait_data-if-rcv_wnd-is-zero.patch
and it can be found in the queue-3.5 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 614cf46bd6e320f786593179b5a36898f9f3c58b Mon Sep 17 00:00:00 2001
From: Michal KubeÄek <[email protected]>
Date: Fri, 14 Sep 2012 04:59:52 +0000
Subject: tcp: flush DMA queue before sk_wait_data if rcv_wnd is zero
From: =?UTF-8?q?Michal=20Kube=C4=8Dek?= <[email protected]>
[ Upstream commit 15c041759bfcd9ab0a4e43f1c16e2644977d0467 ]
If recv() syscall is called for a TCP socket so that
- IOAT DMA is used
- MSG_WAITALL flag is used
- requested length is bigger than sk_rcvbuf
- enough data has already arrived to bring rcv_wnd to zero
then when tcp_recvmsg() gets to calling sk_wait_data(), receive
window can be still zero while sk_async_wait_queue exhausts
enough space to keep it zero. As this queue isn't cleaned until
the tcp_service_net_dma() call, sk_wait_data() cannot receive
any data and blocks forever.
If zero receive window and non-empty sk_async_wait_queue is
detected before calling sk_wait_data(), process the queue first.
Signed-off-by: Michal Kubecek <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
net/ipv4/tcp.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1706,8 +1706,14 @@ int tcp_recvmsg(struct kiocb *iocb, stru
}
#ifdef CONFIG_NET_DMA
- if (tp->ucopy.dma_chan)
- dma_async_memcpy_issue_pending(tp->ucopy.dma_chan);
+ if (tp->ucopy.dma_chan) {
+ if (tp->rcv_wnd == 0 &&
+ !skb_queue_empty(&sk->sk_async_wait_queue)) {
+ tcp_service_net_dma(sk, true);
+ tcp_cleanup_rbuf(sk, copied);
+ } else
+
dma_async_memcpy_issue_pending(tp->ucopy.dma_chan);
+ }
#endif
if (copied >= target) {
/* Do not sleep, just process backlog. */
Patches currently in stable-queue which might be from [email protected] are
queue-3.5/tcp-flush-dma-queue-before-sk_wait_data-if-rcv_wnd-is-zero.patch
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