re: kern/16789

[matthew green <mrg%eterna.com.au@localhost>]

>  >  dump to unopened disk fails (e.g. dump do wd1b when wd1a not mounted), due
>  >  to the open path executing ata_get_params(), which eventually tsleeps()
>  >  while waiting for the command to finish; specifically, if WDF_LOADED is not
>  >  set
>  >  - happens due to wd_get_params() with just AT_WAIT in wdopen()
>  >  - not easy to fix, open needs to read disklabel and all this mechanics
>  >    is too much for emergency crash dump code path
>  
>  Would it be reasonable to open wd1b when it is configured as dump
>  device? I assume if it is also a swap device, it works fine?

this seems like the best way to solve this sanely, though i suspect
it will require some hacks to avoid double-open when also swap device,
but since uvm_swap.c handles these, it should be fairly local hack,
though it will need to handle both dump or swap having the partition
open first, since the admin can set either in any order.


.mrg.