Re: kern/53788: vt switching panic

[mlelstv%serpens.de@localhost (Michael van Elst)]

The following reply was made to PR kern/53788; it has been noted by GNATS.

From: mlelstv%serpens.de@localhost (Michael van Elst)
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: kern/53788: vt switching panic
Date: Sat, 15 Dec 2018 11:44:14 -0000 (UTC)

 dholland%eecs.harvard.edu@localhost writes:
 
 >	Switching from console 4 (running X :0) to console 1 (which
 >	had formerly been running X :1, but the X server had
 >	apparently cored a couple hours earlier without me noticing)
 >	with ctrl-alt-F2 triggered this panic:
 
 >	panic: kernel diagnostic assertion "!cpu_softintr_p()" failed: file "../../../../kern/subr_kmem.c", line 389 
 
 The usl_syncdata structure is usually allocated by the program that
 tries to own the display and freed when it returns ownership after
 being sent a signal. Both operations are done by an ioctl in process
 context.
 
 But when the owner process has died and someone tries to switch
 the display with ctrl-alt-fX, the free operation is done by the
 keyboard interrupt handler.
 
 Usually you don't see this as the X server catches most signals,
 even segfaults, and tries to give back ownership before it exits.
 
 -- 
 -- 
                                 Michael van Elst
 Internet: mlelstv%serpens.de@localhost
                                 "A potential Snark may lurk in every tree."