From: Michal Kubeček Date: Fri, 14 Sep 2012 04:59:52 +0000 (+0000) Subject: tcp: flush DMA queue before sk_wait_data if rcv_wnd is zero X-Git-Tag: v3.2.31~17 X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=f189aa26fd4f45d4f445d8de85d1b29c6ba92982;hp=242582dfc34fb64481d6466cbf816768356d2494 tcp: flush DMA queue before sk_wait_data if rcv_wnd is zero [ 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 Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings --- diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 043d49b39c09..7397ad806f4c 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1589,8 +1589,14 @@ int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg, } #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. */