After vibration, Projecteur constantly uses one core

[mayanksuman]

After vibration, the program constantly use one of core for 100% time.

To reproduce:

1. Open Projecteur and system monitor.
2. Connect Spotlight USB.
3. In Projecteur preferences, go to device tab and select 'Vibration Timer'
4. Click 'Test' in Vibration settings.

The device will vibrate but this point onwards the application use one core continuously as visible in Gnome system monitor.

OS: Debian Testing

• Desktop/Window Manager and Version: Gnome 3.28

• Did you built Projecteur yourself?: [y/n] n

• What is the output of projecteur -f ?: ... Projecteur 0.9.1

  • git-branch: master
  • git-hash: 483d4a36e72de3c00f3d7f76207cc73e5a88a812
  • compiler: GNU 8.3.0
  • qt-version: (build: 5.11.3, runtime: 5.15.2)
  • device-scan: (errors: 0, devices: 1 [readable: 1, writable: 1])

• What is the output of projecteur -d ?: ... Projecteur 0.9.1; device scan

  • Found 1 supported devices. (1 readable, 1 writable)

  +++ name: 'Logitech USB Receiver' userName: 'Logitech Spotlight (USB)' vendorId: 046d productId: c53e phys: usb-0000:04:00.3-2 busType: USB devices: /dev/hidraw6, /dev/input/event22, /dev/input/event24, /dev/input/event23, /dev/input/event25 readable: true writable: true

[jahnf]

Hi Mayank, thanks for reporting, I will see if I can reproduce this. Will request more info from your side if necessary.

[mayanksuman]

I think that calling write in device-vibrate.cc:431 (on socket attached to Read Only QSocketNotifier) is causing this issue. Flame graph generated for the application (using perf for 1 minute of activity) after the device has vibrated show some call to QSocketNotifier and a lot of system calls.

Among the system calls, call to poll is prominent, which suggests that program is checking for an event on a file descriptor (of HID device).