Re: Hotplug events vs proc - timing

[Ivan Gyurdiev <ivg2@cornell.edu>]

Greg KH wrote:
> On Wed, Jun 02, 2004 at 01:36:09PM -0400, Bill Nottingham wrote:
> 
>>Greg KH (greg@kroah.com) said: 
>>
>>>On Tue, Jun 01, 2004 at 01:32:22PM -0600, Ivan Gyurdiev wrote:
>>>
>>>>Fedora's updfstab tool (part of kudzu) is trigged by hotplug to 
>>>>add/remove things from fstab, such as my Fujifilm Digital Camera 
>>>>(usb-storage, scsi emulation). However... it reads /proc/scsi/scsi, and 
>>>>doesn't work as it should because it's triggered before /proc/scsi/scsi 
>>>>is updated most of the time. Where is the bug, and how should this race 
>>>>be corrected?
>>>
>>>The race should be fixed by having the hotplug script wait around for
>>>the proc file to show up.

The proc file is already there. It says "Attached Devices:" and that's 
it. The question here is when the /proc/scsi/scsi file is updated to say 
that I have a digital camera attached. It seems any sort of delay fixes 
it - if I run kudzu from the startup script it works, if I modprobe 
usb-storage out so it has to load it it works (delay while loading?).
If I sleep 1 it works too..

otherwise the old file is read, and no scsi devices are found.
How do we know when the /proc/scsi/scsi file is updated?

>>Hm, as I was thinking, the hotplug event is triggered by the USB
>>insertion; what's really needed for updfstab is that it gets
>>run triggered on the *scsi* device creation. Or is this the proc
>>file you're referring too?
> 
> 
> Yes, good point, you should update the fstab after the device node is
> created.  You can learn of that by putting your script in the
> /etc/dev.d/ directory tree.

FC2 does not use udev. I'd like to use udev, but I understand there are 
early userspace issues to resolve. Last time I tried it did not work 
well for me, since init wouldn't start.







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