Re: kern/53506: Easy trigger of "panic: biodone2 already" on NetBSD 8.0 Xen domU

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

The following reply was made to PR port-xen/53506; 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: Emmanuel Dreyfus <manu%netbsd.org@localhost>
Subject: Re: kern/53506: Easy trigger of "panic: biodone2 already" on NetBSD
 8.0 Xen domU
Date: Mon, 20 Aug 2018 21:51:11 +0200

 2018-08-20 3:40 GMT+02:00 Emmanuel Dreyfus <manu%netbsd.org@localhost>:
 >  The attached patch clears the struct xbd_req content between usage,
 >  while there adds a few sanity checks. At mine it is enough to
 >  prevent any panic on biodone2 already.
 
 This is interesting, since according to how I read the code, it should
 not actually change the behaviour. The fields are not checked
 anywhere, so it should just process the thing same way as before and
 hence panic. Also very likely, if you add xbd_xbdreq_clear() also for
 the DIOCCACHESYNC path, it would trigger panic too :)
 
 I've noticed there is possibly missing splbio()/splx() in
 xbd_diskstart(). Can you try if following patch (without your changes)
 changes the behaviour?
 
 http://www.netbsd.org/~jdolecek/xbd_diskstart_splbio.diff
 
 Jaromir