touch-packages team mailing list archive

[Alexander Ponyatykh <1455924@xxxxxxxxxxxxxxxxxx>]

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
Touch seeded packages, which is subscribed to libusb in Ubuntu.
https://bugs.launchpad.net/bugs/1455924

Title:
  libusb occasionally hungs after suspend/resume

Status in libusb package in Ubuntu:
  New

Bug description:
  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 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
  SourcePackage: libusb
  UpgradeStatus: Upgraded to vivid on 2015-04-26 (21 days ago)

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