Description of problem:

Clicking on the little "up" arrow next to a mounted usb-storage device, which normally unmounts it, hangs thunar.

This appears to be happening only in the F26 build of Thunar. The same version-release on F25 is fine.

Version-Release number of selected component (if applicable):

Thunar-1.6.11-1.fc26.x86_64

How reproducible:

Always

Steps to Reproduce:
1. Update F25 to F26
2. Log in, insert a USB thumb drive. Run thunar
3. Click on the up arrow to unmount the usb-storage device

Actual results:

The thunar process hangs and no longer responds to any input.

Expected results:

The device is unmounted.

Additional info:

straceing the Thunar process shows:

futex(0x7fd7fe16dae0, FUTEX_WAKE_PRIVATE, 1) = 0
write(9, "\1\0\0\0\0\0\0\0", 8)         = 8
futex(0x560aed100380, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0x560aed1000a0, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0x560aed0f80a8, FUTEX_WAKE_PRIVATE, 1) = 1
eventfd2(0, EFD_CLOEXEC|EFD_NONBLOCK)   = 17
futex(0x7fd7fe8f6218, FUTEX_WAIT_PRIVATE, 2, NULL) = -1 EAGAIN (Resource temporarily unavailable)
futex(0x7fd7fe8f6218, FUTEX_WAKE_PRIVATE, 1) = 0
futex(0x560aed102fb0, FUTEX_WAKE_PRIVATE, 1) = 0
write(9, "\1\0\0\0\0\0\0\0", 8)         = 8
futex(0x560aed100380, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0x560aed1000a0, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0x560aed0f80a8, FUTEX_WAKE_PRIVATE, 1) = 1
poll([{fd=17, events=POLLIN}], 1, 25000 <unfinished ...>) = ?

and it never returns from poll().

Looking in /proc, fd 17 is an anonymous eventfd file descriptor.