This patch adds recovery from false busy state on concurrent attach
operation.
The procedure of attach operation is as below.
1) Find an unused port in /sys/devices/platform/vhci_hcd/status.
(userspace)
2) Request attach found port to driver through
/sys/devices/platform/vhci_hcd/attach. (userspace)
3) Lock table, reserve requested port and unlock table. (vhci driver)
Attaching more than one remote devices concurrently, same unused port
number will be found in step-1. Then one request will succeed and
others will fail even though there are some unused ports.
It is possible to avoid this fail by introdocing userspace exclusive
control. But it's exaggerated for this special condition. The locking
itself is done in driver.
With this patch, driver returns EBUSY when requested port has already
been used. In this case, attach command retries from step-1: finding
another unused port. If there's no unused port, the attach operation
will fail. Othrwise it retries automatically using new free port.
Currunt userspace src/usbip_attach.c:import_device() doesn't use the
errno.
vhci-hcd's interface (only errno) is changed as following.
Current errno New errno Condition
EINVAL same as left specified port numbre is in invalid
range
EAGAIN same as left platform_get_drvdata() failed
EINVAL same as left specified socket fd is not valid
EINVAL EBUSY specified port status is not free
Signed-off-by: Nobuo Iwata <nobuo.iwata@xxxxxxxxxxxxxxx>
---
drivers/usb/usbip/vhci_sysfs.c | 8 ++++++--
tools/usb/usbip/src/usbip_attach.c | 28 +++++++++++++++-------------
2 files changed, 21 insertions(+), 15 deletions(-)
diff --git a/drivers/usb/usbip/vhci_sysfs.c b/drivers/usb/usbip/vhci_sysfs.c
index b96e5b1..5d4be4b 100644
--- a/drivers/usb/usbip/vhci_sysfs.c
+++ b/drivers/usb/usbip/vhci_sysfs.c
@@ -214,7 +214,7 @@ static ssize_t store_detach(struct device *dev, struct device_attribute *attr,
ret = vhci_port_disconnect(hcd_to_vhci(hcd), rhport);
if (ret < 0)
- return -EINVAL;
+ return ret;
usbip_dbg_vhci_sysfs("Leave\n");
@@ -314,7 +314,11 @@ static ssize_t store_attach(struct device *dev, struct device_attribute *attr,
sockfd_put(socket);
dev_err(dev, "port %d already used\n", rhport);
- return -EINVAL;
+ /*
+ * Will be retried from userspace
+ * if there's another free port.
+ */
+ return -EBUSY;
}
dev_info(dev, "pdev(%u) rhport(%u) sockfd(%d)\n",
diff --git a/tools/usb/usbip/src/usbip_attach.c b/tools/usb/usbip/src/usbip_attach.c
index 70a6b50..695b2e5 100644
--- a/tools/usb/usbip/src/usbip_attach.c
+++ b/tools/usb/usbip/src/usbip_attach.c
@@ -101,20 +101,22 @@ static int import_device(int sockfd, struct usbip_usb_device *udev)
return -1;
}
- port = usbip_vhci_get_free_port();
- if (port < 0) {
- err("no free port");
- usbip_vhci_driver_close();
- return -1;
- }
+ do {
+ port = usbip_vhci_get_free_port();
+ if (port < 0) {
+ err("no free port");
+ usbip_vhci_driver_close();
+ return -1;
+ }
- rc = usbip_vhci_attach_device(port, sockfd, udev->busnum,
- udev->devnum, udev->speed);
- if (rc < 0) {
- err("import device");
- usbip_vhci_driver_close();
- return -1;
- }
+ rc = usbip_vhci_attach_device(port, sockfd, udev->busnum,
+ udev->devnum, udev->speed);
+ if (rc < 0 && errno != EBUSY) {
+ err("import device");
+ usbip_vhci_driver_close();
+ return -1;
+ }
+ } while (rc < 0);
usbip_vhci_driver_close();
--
2.1.0
--
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