Please note that debug message about lost URB is not 100% accurate in multi-threaded code because of harmless race condition.
** Description changed: 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 + I've attached patch with 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 + 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) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1455924 Title: libusb occasionally hungs after suspend/resume To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/libusb/+bug/1455924/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
