Messages in this thread Patch in this message | | | Date | Thu, 16 Dec 2010 23:50:27 +0100 | From | Max Vozeler <> | Subject | Re: usbip: somtimes stalls at kernel_recvmsg() |
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Hi Németh,
On 16.12.2010 08:31, Németh Márton wrote: > Németh Márton wrote: >> I'm working with usbip and I sometimes see a stall when I run >> the "lsusb" command from the userspace.
Does it eventually recover?
>> I added some debug messages >> and it seems that the kernel_recvmsg() in >> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=drivers/staging/usbip/usbip_common.c;h=210ef16bab8d271a52e5d36cd1994aad57ad99e1;hb=HEAD >> >> This is the only place I could find where the TCP messages are arriving in >> the usbip code. >> >> What happens if a message does not arrive? Does it stall forever?
Yes, it will block until detached or until a TCP timeout or error closes the connection.
The TCP timeout can take several minutes.
>> yes, how can the kernel_recvmsg() call changed to handle some timeout? > > I found that the userspace manpage of recvmsg(2) ("man recvmsg") contains description > of the "flags" parameter. I suppose the parameters and behaviour of the userspace > recvmsg() is the same as the kernelspace kernel_recvmsg().
I recently faced this problem, too.
The solution I arrived at was to set SO_RCVTIMEO and SO_SNDTIMEO socket opts in the tools together with the patch below.
The patch works around a lack of heart-beat in the usbip protocol which would otherwise make idle connections time out.
(It wont apply cleanly but hopefully conveys the idea.).
Extending the protocol for a heart-beat message doesn't seem to be possible without breaking the compatibility at the same time.
I was planning to submit it on the weekend along with the tool changes to set the timeouts.
Max
--- From: Max Vozeler <max@vozeler.com> Date: Mon, 13 Dec 2010 00:39:14 +0100 Subject: [PATCH 1/3] vhci: allow SO_RCVTIMEO on the socket
In case of unanswered replies, a receive timeout is considered a connection error and the device will be shut down and removed.
This is a workaround for the lack of heart-beat messages in the USBIP protocol. It allows userspace to set a maximum latency for the connection. --- vhci_rx.c | 21 ++++++++++++++++++++- 1 files changed, 20 insertions(+), 1 deletions(-)
diff --git a/vhci_rx.c b/vhci_rx.c index bc16dc4..9a1fe80 100644 --- a/vhci_rx.c +++ b/vhci_rx.c @@ -197,6 +197,19 @@ static void vhci_recv_ret_unlink(struct vhci_device *vdev, return; } +static int vhci_priv_tx_empty(struct vhci_device *vdev) +{ + int empty = 0; + + spin_lock(&vdev->priv_lock); + + empty = list_empty(&vdev->priv_rx); + + spin_unlock(&vdev->priv_lock); + + return empty; +} + /* recv a pdu */ static void vhci_rx_pdu(struct usbip_device *ud) { @@ -216,8 +229,14 @@ static void vhci_rx_pdu(struct usbip_device *ud) usbip_uinfo("connection reset by peer\n"); else if (ret == -ETIMEDOUT) usbip_uinfo("connection timed out\n"); - else if (ret != -ERESTARTSYS) + else if (ret == -EAGAIN) { + /* connection was idle? */ + if (vhci_priv_tx_empty(vdev)) + return; + usbip_uinfo("connection timed out with pending urbs\n"); + } else if (ret != -ERESTARTSYS) usbip_uinfo("xmit failed %d\n", ret); + usbip_event_add(ud, VDEV_EVENT_ERROR_TCP); return; } -- 1.7.2.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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