[oe] invalidating udev cache, how?

[Mike (mwester)]

Koen Kooi wrote:
...
> My current ideas:
> 
> 1) remove /etc/dev.tar if its > x weeks old
> 2) recreate it on shutdown
> 3) remove it after x times
> 
> option 1) breaks on systems without an RTC and/or no /etc/timestamp
> option 2) moves the slowness to shutdown
> option 3) requires extra logic and filesystem access
> 
> and all options don't fix the first case I mentioned, they all take a
> while to make /dev/fb1 appear.
> 
> The key is that it should be transparent to users, so adding a check for
> .e.g 'ignore_dev.tar=1' in bootargs wouldn't work, since that implies
> that users are aware of the problem and know how to 'fix' it.
> 
> Does anyone have other ways to invalidate the cache, and if not, which
> option would get your vote?

A slight improvement would be to make the dev.tar file dependent upon
the bootargs; i.e. invalidate /etc/dev.tar file if the boot command line
doesn't match the current command line.  This could be a very fast
operation, just "cmp /proc/cmdline /etc/dev_cmdline" or similar.

Mike (mwester)