Re: kern/16789

[Jaromír Doleček <jaromir.dolecek%gmail.com@localhost>]

The following reply was made to PR kern/16789; it has been noted by GNATS.

From: =?UTF-8?B?SmFyb23DrXIgRG9sZcSNZWs=?= <jaromir.dolecek%gmail.com@localhost>
To: "gnats-bugs%NetBSD.org@localhost" <gnats-bugs%netbsd.org@localhost>
Cc: 
Subject: Re: kern/16789
Date: Wed, 24 Oct 2018 21:51:52 +0200

 Some observation from the time when I was implementing NCQ:
 
 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
 
 It would be nice if some brave soul tackled this. One possible avenue
 would be to take advantage of the disklabel being implicitly read on
 swapon, and use the cached information when system opens the device to
 take the dump.
 
 Jaromir