Re: port-amd64/53789: amd64-install.img boot hangs on HP Compaq 8200 Elite

[Andreas Gustafsson <gson%gson.org@localhost>]

The following reply was made to PR port-amd64/53789; it has been noted by GNATS.

From: Andreas Gustafsson <gson%gson.org@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: port-amd64/53789: amd64-install.img boot hangs on HP Compaq 8200 Elite
Date: Mon, 14 Jan 2019 21:12:59 +0200

 This bug is fixed, but I have one more comment for the record.
 
 I was wondering why this caused a silent hang rather than a panic, and
 I now have what seems like a plausible theory.  When aprint_error_dev()
 uses the NULL dev pointer, it takes the address of the dv_xname field
 and ends up with a pointer containing a small positive integer which
 is then passed to printf() and dereferenced while holding kprintf_mtx.
 Presumably this then traps, but printing the trap message tries to
 reacquire kprintf_mtx and deadlocks.
 -- 
 Andreas Gustafsson, gson%gson.org@localhost