Comment 0 for bug 1455924

I'm trying to make g15daemon correctly recover after suspend/resume and found that it occasionally hungs after resume in libusb's usb_urb_transfer() (linux.c) on this line:
ioctl(dev->fd, IOCTL_USB_REAPURB, &context);

After some research I found that linux kernel internally has lists of pending and completed requests. All requests - successful or not - are moved from pending list to completed list, no requests should be lost. But it looks like after suspend/resume some request may be lost (may be a kernel bug). It that case IOCTL_USB_REAPURB would hung forever since request it's waiting for will never appear on completed list.

There is simple workaround. After preceding IOCTL_USB_DISCARDURB call our request is guaranteed to be completed, so there is no need to use blocking IOCTL_USB_DISCARDURB, we may use non-blocking IOCTL_USB_REAPURBNDELAY instead.

I've attached path for this workaround. It also fixes race condition existed in original code, which may cause corruption of stack.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: libusb-0.1-4 2:0.1.12-25 [modified: lib/x86_64-linux-gnu/libusb-0.1.so.4.4.4]
ProcVersionSignature: Ubuntu 3.19.0-16.16-generic 3.19.3
Uname: Linux 3.19.0-16-generic x86_64
NonfreeKernelModules: fglrx
ApportVersion: 2.17.2-0ubuntu1
Architecture: amd64
CurrentDesktop: KDE
Date: Sun May 17 13:11:00 2015
Dependencies:
 gcc-5-base 5.1~rc1-0ubuntu1
 libc6 2.21-0ubuntu4
 libgcc1 1:5.1~rc1-0ubuntu1
 multiarch-support 2.21-0ubuntu4
SourcePackage: libusb
UpgradeStatus: Upgraded to vivid on 2015-04-26 (21 days ago)