.\"     $NetBSD: panic.9,v 1.15 2003/04/16 13:35:31 wiz Exp $
.\"
.\" Copyright (c) 1996 Michael Graff.
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.Dd September 27, 2002
.Dt PANIC 9
.Os
.Sh NAME
.Nm panic
.Nd Bring down system on fatal error
.Sh SYNOPSIS
.In sys/types.h
.In sys/systm.h
.Ft void
.Fn panic "const char *fmt" "..."
.Sh DESCRIPTION
The
.Fn panic
function terminates the
.Nx
system.
The message
.Fa fmt
is a
.Xr printf 3
style format string which is printed to the console and saved in the
variable
.Va panicstr
for later retrieval via core dump inspection.
A newline character is added at the end automatically, and is thus
not needed in the format string.
.Pp
If a kernel debugger is installed, control is passed to it after the
message is printed.
If the kernel debugger is
.Xr ddb 4 ,
control is only passed if the value of the
.Em ddb.onpanic
.Xr sysctl 3
is
.Dq 1 ,
otherwise, a
.Xr ddb 4 Ns -specific
function is used to print the kernel stack trace, and then control returns
to
.Fn panic .
.Pp
If control remains in
.Fn panic ,
an attempt is made to save an image of system memory on the
configured dump device.
.Pp
If during the process of handling the panic,
.Fn panic
is called again
.Pq from the filesystem synchronization routines, for example ,
the system is rebooted immediately without synchronizing any filesystems.
.Sh RETURN VALUES
The
.Fn panic
function does not return.
.Sh SEE ALSO
.Xr sysctl 3 ,
.Xr ddb 4 ,
.Xr ipkdb 4 ,
.Xr options 4 ,
.Xr savecore 8 ,
.Xr swapctl 8 ,
.Xr sysctl 8