You're right Martin, the problem comes from the kernel, which goes on detecting USB connections although my USB device is disconnnected. (and furthermore, it cannot handle the USB device).
Here is /var/log/kernel.log: tail -f /var/log/kern.log Feb 15 11:29:48 lsro1pc307 kernel: [79503.404000] usb 1-1: new full speed USB device using uhci_hcd and address 2 Feb 15 11:29:48 lsro1pc307 kernel: [79503.596000] usb 1-1: configuration #1 chosen from 1 choice Feb 15 11:29:48 lsro1pc307 kernel: [79503.992000] usbcore: registered new interface driver usbserial Feb 15 11:29:48 lsro1pc307 kernel: [79503.992000] drivers/usb/serial/usb-serial.c: USB Serial support registered for generic Feb 15 11:29:49 lsro1pc307 kernel: [79504.084000] usbcore: registered new interface driver usbserial_generic Feb 15 11:29:49 lsro1pc307 kernel: [79504.084000] drivers/usb/serial/usb-serial.c: USB Serial Driver core Feb 15 11:29:49 lsro1pc307 kernel: [79504.096000] drivers/usb/serial/usb-serial.c: USB Serial support registered for FTDI USB Serial Device Feb 15 11:29:49 lsro1pc307 kernel: [79504.096000] ftdi_sio 1-1:1.0: FTDI USB Serial Device converter detected Feb 15 11:29:49 lsro1pc307 kernel: [79504.096000] drivers/usb/serial/ftdi_sio.c: Detected FT232BM Feb 15 11:29:49 lsro1pc307 kernel: [79504.096000] usb 1-1: FTDI USB Serial Device converter now attached to ttyUSB0 Feb 15 11:29:49 lsro1pc307 kernel: [79504.096000] usbcore: registered new interface driver ftdi_sio Feb 15 11:29:49 lsro1pc307 kernel: [79504.096000] drivers/usb/serial/ftdi_sio.c: v1.4.3:USB FTDI Serial Converters Driver Feb 15 11:29:49 lsro1pc307 kernel: [79504.300000] usb 1-1: usbfs: interface 0 claimed by ftdi_sio while 'brltty' sets config #1 Feb 15 11:29:49 lsro1pc307 kernel: [79504.304000] ftdi_sio ttyUSB0: FTDI USB Serial Device converter now disconnected from ttyUSB0 Feb 15 11:29:49 lsro1pc307 kernel: [79504.304000] ftdi_sio 1-1:1.0: device disconnected Feb 15 11:30:00 lsro1pc307 kernel: [79515.572000] usb 1-1: USB disconnect, address 2 Feb 15 11:30:00 lsro1pc307 kernel: [79515.684000] usb 1-1: new full speed USB device using uhci_hcd and address 3 Feb 15 11:30:00 lsro1pc307 kernel: [79515.876000] usb 1-1: configuration #1 chosen from 1 choice Feb 15 11:30:00 lsro1pc307 kernel: [79515.880000] ftdi_sio 1-1:1.0: FTDI USB Serial Device converter detected Feb 15 11:30:00 lsro1pc307 kernel: [79515.880000] drivers/usb/serial/ftdi_sio.c: Detected FT232BM Feb 15 11:30:00 lsro1pc307 kernel: [79515.880000] usb 1-1: FTDI USB Serial Device converter now attached to ttyUSB0 Feb 15 11:30:06 lsro1pc307 kernel: [79521.032000] usb 1-1: usbfs: interface 0 claimed by ftdi_sio while 'brltty' sets config #1 Feb 15 11:30:06 lsro1pc307 kernel: [79521.036000] ftdi_sio ttyUSB0: FTDI USB Serial Device converter now disconnected from ttyUSB0 Feb 15 11:30:06 lsro1pc307 kernel: [79521.036000] ftdi_sio 1-1:1.0: device disconnected Feb 15 11:30:11 lsro1pc307 kernel: [79526.516000] usb 4-2: USB disconnect, address 4 Feb 15 11:30:11 lsro1pc307 kernel: [79526.628000] usb 4-2: new full speed USB device using uhci_hcd and address 5 Feb 15 11:30:11 lsro1pc307 kernel: [79526.860000] usb 4-2: configuration #1 chosen from 1 choice Feb 15 11:30:12 lsro1pc307 kernel: [79526.972000] usb 1-1: USB disconnect, address 3 Feb 15 11:30:12 lsro1pc307 kernel: [79527.084000] usb 1-1: new full speed USB device using uhci_hcd and address 4 Feb 15 11:30:12 lsro1pc307 kernel: [79527.276000] usb 1-1: configuration #1 chosen from 1 choice Feb 15 11:30:12 lsro1pc307 kernel: [79527.280000] ftdi_sio 1-1:1.0: FTDI USB Serial Device converter detected Feb 15 11:30:12 lsro1pc307 kernel: [79527.280000] drivers/usb/serial/ftdi_sio.c: Detected FT232BM Feb 15 11:30:12 lsro1pc307 kernel: [79527.280000] usb 1-1: FTDI USB Serial Device converter now attached to ttyUSB0 Feb 15 11:30:17 lsro1pc307 kernel: [79532.432000] usb 1-1: usbfs: interface 0 claimed by ftdi_sio while 'brltty' sets config #1 Feb 15 11:30:17 lsro1pc307 kernel: [79532.436000] ftdi_sio ttyUSB0: FTDI USB Serial Device converter now disconnected from ttyUSB0 Feb 15 11:30:17 lsro1pc307 kernel: [79532.436000] ftdi_sio 1-1:1.0: device disconnected Feb 15 11:30:28 lsro1pc307 kernel: [79543.668000] usb 1-1: USB disconnect, address 4 Feb 15 11:30:28 lsro1pc307 kernel: [79543.780000] usb 1-1: new full speed USB device using uhci_hcd and address 5 Feb 15 11:30:29 lsro1pc307 kernel: [79543.972000] usb 1-1: configuration #1 chosen from 1 choice Feb 15 11:30:29 lsro1pc307 kernel: [79543.976000] ftdi_sio 1-1:1.0: FTDI USB Serial Device converter detected Feb 15 11:30:29 lsro1pc307 kernel: [79543.976000] drivers/usb/serial/ftdi_sio.c: Detected FT232BM Feb 15 11:30:29 lsro1pc307 kernel: [79543.976000] usb 1-1: FTDI USB Serial Device converter now attached to ttyUSB0 Feb 15 11:30:34 lsro1pc307 kernel: [79549.128000] usb 1-1: usbfs: interface 0 claimed by ftdi_sio while 'brltty' sets config #1 Feb 15 11:30:34 lsro1pc307 kernel: [79549.132000] ftdi_sio ttyUSB0: FTDI USB Serial Device converter now disconnected from ttyUSB0 Feb 15 11:30:34 lsro1pc307 kernel: [79549.132000] ftdi_sio 1-1:1.0: device disconnected Feb 15 11:30:39 lsro1pc307 kernel: [79554.612000] usb 4-2: USB disconnect, address 5 Feb 15 11:30:39 lsro1pc307 kernel: [79554.724000] usb 4-2: new full speed USB device using uhci_hcd and address 6 Feb 15 11:30:40 lsro1pc307 kernel: [79554.900000] usb 4-2: configuration #1 chosen from 1 choice Feb 15 11:30:46 lsro1pc307 kernel: [79561.352000] usb 1-1: USB disconnect, address 5 Feb 15 11:31:38 lsro1pc307 kernel: [79612.840000] usb 4-2: USB disconnect, address 6 Feb 15 11:31:38 lsro1pc307 kernel: [79612.952000] usb 4-2: new full speed USB device using uhci_hcd and address 7 Feb 15 11:31:38 lsro1pc307 kernel: [79613.128000] usb 4-2: configuration #1 chosen from 1 choice Feb 15 11:31:53 lsro1pc307 kernel: [79628.684000] usb 4-2: USB disconnect, address 7 Feb 15 11:31:54 lsro1pc307 kernel: [79628.852000] usb 4-2: new full speed USB device using uhci_hcd and address 8 Feb 15 11:31:54 lsro1pc307 kernel: [79629.028000] usb 4-2: configuration #1 chosen from 1 choice Feb 15 11:31:59 lsro1pc307 kernel: [79634.220000] usb 4-2: USB disconnect, address 8 Feb 15 11:31:59 lsro1pc307 kernel: [79634.332000] usb 4-2: new full speed USB device using uhci_hcd and address 9 Feb 15 11:31:59 lsro1pc307 kernel: [79634.508000] usb 4-2: configuration #1 chosen from 1 choice Feb 15 11:32:10 lsro1pc307 kernel: [79644.888000] usb 4-2: USB disconnect, address 9 Feb 15 11:32:10 lsro1pc307 kernel: [79645.000000] usb 4-2: new full speed USB device using uhci_hcd and address 10 Feb 15 11:32:10 lsro1pc307 kernel: [79645.176000] usb 4-2: configuration #1 chosen from 1 choice Feb 15 11:32:20 lsro1pc307 kernel: [79655.536000] usb 4-2: USB disconnect, address 10 Feb 15 11:32:21 lsro1pc307 kernel: [79655.648000] usb 4-2: new full speed USB device using uhci_hcd and address 11 Feb 15 11:32:21 lsro1pc307 kernel: [79655.880000] usb 4-2: configuration #1 chosen from 1 choice Feb 15 11:32:26 lsro1pc307 kernel: [79661.056000] usb 4-2: USB disconnect, address 11 Feb 15 11:32:26 lsro1pc307 kernel: [79661.224000] usb 4-2: new full speed USB device using uhci_hcd and address 12 Feb 15 11:32:26 lsro1pc307 kernel: [79661.400000] usb 4-2: configuration #1 chosen from 1 choice -- adds/removes same device many times a second causing high loads and extremally slow performance https://launchpad.net/bugs/81915 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
