improve panic man pages and document nix' ndnr, and
detail the behavior panic

Reference: /n/atom/patch/applied2013/panicndnr
Date: Sun Dec 29 15:44:08 CET 2013
Signed-off-by: quanstro@quanstro.net

--- /sys/man/9/panic	Sun Dec 29 15:43:15 2013
+++ /sys/man/9/panic	Sun Dec 29 15:43:15 2013
@@ -4,8 +4,25 @@
 .SH SYNOPSIS
 .ta \w'\fLchar* 'u
 .B
+void	archreset(void)
+.br
+.B
+void	exit(int ispanic)
+.br
+.B
 void	panic(char *fmt, ...)
 .SH DESCRIPTION
+.I Archreset
+reboots the machine.
+.PP
+Depending on configuration settings, the platform-dependent
+.I exit
+might reboot the system.  If
+.I ispanic
+is set,
+.I panic
+is called.
+.PP
 .I Panic
 writes a message to the console and
 causes the system to give up the ghost.
@@ -23,3 +40,8 @@
 adds a prefix
 .L "panic: "
 and a trailing newline.
+.SH "SEE ALSO"
+.IR panic (9nix)
+.SH BUGS
+Note the differences with
+.IR panic (9nix).
--- /sys/man/9nix/panic	Thu Jan  1 00:00:00 1970
+++ /sys/man/9nix/panic	Sun Dec 29 15:43:16 2013
@@ -0,0 +1,62 @@
+.TH PANIC 9nix
+.SH NAME
+archreset, exit, panic, ndnr \- abandon hope
+.SH SYNOPSIS
+.ta \w'\fLchar* 'u
+.B
+void	archreset(void)
+.br
+.B
+void	exit(int ispanic)
+.br
+.B
+void	ndnr(void)
+.br
+.B
+void	panic(char *fmt, ...)
+.SH DESCRIPTION
+.PP
+.I Archreset
+reboots the machine.
+.PP
+Depending on configuration settings, the platform-dependent
+.I exit
+might reboot the system.  If
+.I ispanic
+is set,
+.I panic
+is called.
+.PP
+.I Ndnr
+(no deposit, no return)
+disables all
+interrupt sources and halts the current processor.
+.PP
+.I Panic
+writes a message to the console and
+causes the system to give up the ghost.
+It disables interrupts, dumps the kernel stack,
+and halts the current processor;
+if more than one, others will gradually come to a halt.
+A subsequent
+.I panic
+on a different processor will halt that processor with
+.IR ndnr;
+a recursive
+.I panic
+will reboot the machine with
+.IR archreset.
+.PP
+The format
+.I fmt
+and associated arguments are the same as those for
+.IR print (9).
+.I Panic
+adds a prefix
+.L "panic: cpu\fIn\fP:"
+and a trailing newline.
+.SH "SEE ALSO"
+.IR panic (9)
+.SH BUGS
+Note the differences with
+.IR panic (9).