Nobuo Iwata a38711a88b usbip: auto retry for concurrent attach ... 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. 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 in step-1. Otherwise it retries automatically using another unused port. vhci-hcd's interface (only errno) is changed as following. Current errno New errno Condition EINVAL same as left specified port number 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 The errno EBUSY was not used in userspace src/usbip_attach.c:import_device(). It is needed to distinguish the condition to be able to retry from other unrecoverable errors. It is possible to avoid this failure by introducing userspace exclusive control. But it's exaggerated for this special condition. The locking itself has done in driver. As an alternate solution, userspace doesn't specify port number, driver searches unused port and it returns port number to the userspace. With this solution, the interface is much different than this patch. Signed-off-by: Nobuo Iwata <nobuo.iwata@fujixerox.co.jp> Acked-by: Shuah Khan <shuahkh@osg.samsung.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2017-08-31 18:08:45 +02:00
..
ffs-aio-example
usbip	usbip: auto retry for concurrent attach	2017-08-31 18:08:45 +02:00
.gitignore
ffs-test.c
hcd-tests.sh
Makefile
testusb.c