Re: cold plugging

["Alexander E. Patrakov" <patrakov@gmail.com>]

(reposting from a different address, since SpamCop blacklisted the SMTP 
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Kay Sievers wrote:

>On Sat, Jan 14, 2006 at 06:10:48PM +0500, Alexander E. Patrakov wrote:
>  
>
>>Kay Sievers wrote:
>>    
>>
>>>On Sat, Jan 14, 2006 at 10:00:29AM +0500, Alexander E. Patrakov wrote:
>>>      
>>>
>>>>Greg KH wrote:
>>>>
>>>>        
>>>>
>>>>>Why does USB take longer for you?  What is taking such a long time?
>>>>>
>>>>>          
>>>>>
>>>>The /dev/bus/usb/... node for my Mustek Plug-N-Scan 1200 UB Plus scanner.
>>>>        
>>>>
>>>It's the simplest way to wait for all events. Depending how you handle
>>>dependencies/checkoints on bootup, it may be sudfficient if all localfs
>>>devices have appeared and you can let the other events finish 
>>>asynchronously.
>>>
>>>
>>>      
>>>
>>Thanks, but you probably missed the point. Your loop does NOT wait for 
>>all events. I think that in my case the following happens:
>>
>>1) The script creates an empty /dev/.udev/queue directory
>>2) The script causes the kernel to emit uevents
>>3) udevd gets those uevents, and reacts upon them. This reaction 
>>involves, among other things, making device nodes and calling 
>>/sbin/modprobe to load new drivers.
>>4) Those drivers are bound to devices by the kernel, this produces new 
>>uevents, go to (3).
>>5) When the internal queue of udevd becomes empty, it removes the 
>>/dev/.udev/queue directory and the loop exits.
>>
>>The problem is that some modules take longer than 0.1s to detect their 
>>hardware, so there is a period of time longer than 0.1s with the empty 
>>udevd queue, after which new uevents arrive.
>>    
>>
>
>Which modprobe for which module is it, that returns before events for
>the devices are generated?
>
>  
>
Sorry, after playing with udev versions and changing rules, I lost my
ability to reproduce this with my scanner alone. But this does happen
when I boot with both my scanner and my MP3 player plugged in. Leaked
events (i.e.: those that happen within 2 seconds after the end of the
loop) are pasted at the end of this mail, so I assume that it is related
with usb_storage for this report. Note that if I boot with only one of
those devices, nothing leaks.

UDEV_LOG=0
ACTION­d
DEVPATH=/devices/pci0000:00/0000:00:07.2/usb1/1-2
SUBSYSTEM=usb
SEQNUM\x1518
PHYSDEVBUS=usb
PHYSDEVDRIVER=usb
- -------------------------------------
UDEV_LOG=0
ACTION­d
DEVPATH=/devices/pci0000:00/0000:00:07.2/usb1/1-2/1-2:1.0
SUBSYSTEM=usb
SEQNUM\x1519
PHYSDEVBUS=usb
DEVICE=/proc/bus/usb/001/003
PRODUCTA9/a002/100
TYPE=0/0/0
INTERFACE=8/6/80
MODALIAS=usb:v0419pA002d0100dc00dsc00dp00ic08isc06ip50
UDEVD_EVENT=1
- -------------------------------------
UDEV_LOG=0
ACTION­d
DEVPATH=/class/usb_device/usbdev1.3
SUBSYSTEM=usb_device
SEQNUM\x1520
PHYSDEVPATH=/devices/pci0000:00/0000:00:07.2/usb1/1-2
PHYSDEVBUS=usb
PHYSDEVDRIVER=usb
MAJOR\x189
MINOR=2
UDEVD_EVENT=1
DEVNAME=/dev/bus/usb/001/003
- -------------------------------------
UDEV_LOG=0
ACTION­d
DEVPATH=/class/scsi_host/host0
SUBSYSTEM=scsi_host
SEQNUM\x1526
PHYSDEVPATH=/devices/pci0000:00/0000:00:07.2/usb1/1-2/1-2:1.0/host0
UDEVD_EVENT=1

-- 
Alexander E. Patrakov


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