| 1 | Debugging the udev event processing
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| 2 | ===================================
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| 3 |
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| 4 | To visualize the driver core events and the udev event processes, use:
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| 5 | udevmonitor
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| 6 |
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| 7 | it prints:
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| 8 | UEVENT[1132632714.285362] add@/devices/pci0000:00/0000:00:1d.1/usb2/2-2
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| 9 | UEVENT[1132632714.288166] add@/devices/pci0000:00/0000:00:1d.1/usb2/2-2/2-2:1.0
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| 10 | UEVENT[1132632714.309485] add@/class/input/input6
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| 11 | UEVENT[1132632714.309511] add@/class/input/input6/mouse2
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| 12 | UEVENT[1132632714.309524] add@/class/usb_device/usbdev2.12
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| 13 | UDEV [1132632714.348966] add@/devices/pci0000:00/0000:00:1d.1/usb2/2-2
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| 14 | UDEV [1132632714.420947] add@/devices/pci0000:00/0000:00:1d.1/usb2/2-2/2-2:1.0
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| 15 | UDEV [1132632714.427298] add@/class/input/input6
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| 16 | UDEV [1132632714.434223] add@/class/usb_device/usbdev2.12
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| 17 | UDEV [1132632714.439934] add@/class/input/input6/mouse2
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| 18 |
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| 19 | UEVENT lines show the events the kernel sends over netlink, the UDEV lines
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| 20 | show the finished udev event handlers. The timing is printed in microseconds.
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| 21 | The time between UEVENT and UDEV is the time udev took to process this event
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| 22 | or was queued to synchronize it with other events.
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| 23 |
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| 24 | If called with:
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| 25 | udevmonitor --env
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| 26 |
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| 27 | it prints the whole event environment:
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| 28 | UDEV [1132633002.937243] add@/class/input/input7
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| 29 | UDEV_LOG=3
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| 30 | ACTION=add
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| 31 | DEVPATH=/class/input/input7
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| 32 | SUBSYSTEM=input
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| 33 | SEQNUM=1043
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| 34 | PHYSDEVPATH=/devices/pci0000:00/0000:00:1d.1/usb2/2-2/2-2:1.0
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| 35 | PHYSDEVBUS=usb
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| 36 | PHYSDEVDRIVER=usbhid
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| 37 | PRODUCT=3/46d/c03e/2000
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| 38 | NAME="Logitech USB-PS/2 Optical Mouse"
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| 39 |
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| 40 |
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| 41 | Udev also sends messages to syslog according to the configured debugging
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| 42 | level. Udev specific tools which are called, also respect the setting
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| 43 | of udev_log. But there might be some which need special actions to make
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| 44 | them verbose.
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| 45 |
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| 46 | Set udevs loglevel in the damon at runtime with:
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| 47 | udevcontrol log_priority=<level>
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| 48 |
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| 49 | Enable logging permanently, set (it may make udev _very_ slow):
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| 50 | udev_log=info in /etc/udev/udev.conf.
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| 51 |
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| 52 |
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| 53 | For further processing of the logging output you should get a clean logfile at
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| 54 | next boot. Just move the old logfile away. (Syslog will still use the moved file
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| 55 | until it's restarted).
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| 56 |
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| 57 | The script 'show_event_log' provided along with this file, can be used to
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| 58 | extract info out of /var/log/messages. Call it:
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| 59 | show_event_log <first> [<last> [<list of event types>] ]
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| 60 | <first> is the sequence number of the first event you are interested in.
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| 61 | <last> is the number of the last event. You may write 'last' literally. It may
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| 62 | also be omitted if you want to see a single event.
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| 63 | <list> is a list of event types you like to see. If you omit it, you get most
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| 64 | events, not all. Some are exclude by default. Use " " as list if you
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| 65 | want to see really all. Or edit the list of skipped events in the first
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| 66 | lines of the script
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| 67 |
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| 68 | If you don't use /var/log/messages as the logfile you may set the environment
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| 69 | variable MESSAGES=<logfile>.
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| 70 |
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