212 lines
5.4 KiB
Groff
212 lines
5.4 KiB
Groff
.\"
|
|
.\" Copyright (c) 1996 Joerg Wunsch
|
|
.\"
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
|
|
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
|
|
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
|
|
.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
|
|
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
|
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
|
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
|
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
|
|
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd July 21, 1996
|
|
.Os
|
|
.Dt SPL 9
|
|
.Sh NAME
|
|
.Nm splbio ,
|
|
.Nm splclock ,
|
|
.Nm splhigh ,
|
|
.Nm splimp ,
|
|
.Nm splnet ,
|
|
.Nm splsoftclock ,
|
|
.Nm splsofttty ,
|
|
.Nm splstatclock ,
|
|
.Nm spltty ,
|
|
.Nm splvm ,
|
|
.Nm spl0 ,
|
|
.Nm splx
|
|
.Nd manipulate interrupt priorities
|
|
.Sh SYNOPSIS
|
|
.In sys/types.h
|
|
.In sys/systm.h
|
|
.Ft intrmask_t
|
|
.Fn splbio "void"
|
|
.Ft intrmask_t
|
|
.Fn splclock "void"
|
|
.Ft intrmask_t
|
|
.Fn splhigh "void"
|
|
.Ft intrmask_t
|
|
.Fn splimp "void"
|
|
.Ft intrmask_t
|
|
.Fn splnet "void"
|
|
.Ft intrmask_t
|
|
.Fn splsoftclock "void"
|
|
.Ft intrmask_t
|
|
.Fn splsofttty "void"
|
|
.Ft intrmask_t
|
|
.Fn splstatclock "void"
|
|
.Ft intrmask_t
|
|
.Fn spltty "void"
|
|
.Ft void
|
|
.Fn spl0 "void"
|
|
.Ft void
|
|
.Fn splx "intrmask_t ipl"
|
|
.Sh DESCRIPTION
|
|
.Bf -symbolic
|
|
This API is deprecated.
|
|
Use mutexes to protect data structures instead.
|
|
See
|
|
.Xr mutex 9
|
|
for more information.
|
|
.Ef
|
|
.Pp
|
|
The
|
|
.Fn spl
|
|
function family sets the interrupt priority
|
|
.Dq level
|
|
of the CPU.
|
|
This prevents interrupt handlers of the blocked priority level from
|
|
being run. This is used in the
|
|
.Dq synchronous
|
|
part of a driver (the part that runs on behalf of the user process) to
|
|
examine or modify data areas that might be examined or modified by
|
|
interrupt handlers.
|
|
.Pp
|
|
Each driver that uses interrupts is normally assigned to an interrupt
|
|
priority group by a keyword in its config line.
|
|
For example:
|
|
.Bd -literal -offset indent
|
|
device foo0 at isa? port 0x0815 irq 12 tty
|
|
.Ed
|
|
.Pp
|
|
assigns interrupt 12 to the
|
|
.Dq tty
|
|
priority group. The system automatically arranges for interrupts in
|
|
the
|
|
.Em xxx
|
|
group to be called at a priority >=
|
|
.Ns spl Ns Em xxx
|
|
\&().
|
|
.Pp
|
|
The function
|
|
.Fn splx
|
|
sets the interrupt priority to an absolute value. The intent is that
|
|
the value returned by the other functions should be saved in a local
|
|
variable, and later passed to
|
|
.Fn splx
|
|
in order to restore the previous priority.
|
|
.Pp
|
|
The function
|
|
.Fn spl0
|
|
lowers the priority to a value where all interrupt handlers are
|
|
unblocked, but ASTs (asynchronous system traps) remain blocked until
|
|
the system is about to return to user mode.
|
|
.Pp
|
|
The traditional assignment of the various device drivers to the
|
|
interrupt priority groups can be roughly classified as:
|
|
.Bl -tag -width Fn
|
|
.It Fn splnet
|
|
Software part of the network interface drivers.
|
|
.It Fn splimp
|
|
All network interface drivers.
|
|
.It Fn splbio
|
|
All
|
|
.Em buffered IO
|
|
(i.e., disk and the like) drivers.
|
|
.It Fn spltty
|
|
Basically, all non-network communications devices, but effectively
|
|
used for all drivers that are neither network nor disks.
|
|
.El
|
|
.Sh RETURN VALUES
|
|
All functions except
|
|
.Fn splx
|
|
and
|
|
.Fn spl0
|
|
return the previous priority value.
|
|
.Sh EXAMPLES
|
|
This is a typical example demonstrating the usage:
|
|
.Bd -literal
|
|
struct foo_softc {
|
|
...
|
|
int flags;
|
|
#define FOO_ASLEEP 1
|
|
#define FOO_READY 2
|
|
|
|
} foo_softc[NFOO];
|
|
|
|
int
|
|
foowrite(...)
|
|
{
|
|
struct foo_softc *sc;
|
|
int s, error;
|
|
|
|
...
|
|
s = spltty();
|
|
if (!(sc->flags & FOO_READY)) {
|
|
/* Not ready, must sleep on resource. */
|
|
sc->flags |= FOO_ASLEEP;
|
|
error = tsleep(sc, PZERO, "foordy", 0);
|
|
sc->flags &= ~FOO_ASLEEP;
|
|
}
|
|
sc->flags &= ~FOO_READY;
|
|
splx(s);
|
|
|
|
...
|
|
}
|
|
|
|
void
|
|
foointr(...)
|
|
{
|
|
struct foo_softc *sc;
|
|
|
|
...
|
|
sc->flags |= FOO_READY;
|
|
if (sc->flags & FOO_ASLEEP)
|
|
/* Somebody was waiting for us, awake him. */
|
|
wakeup(sc);
|
|
...
|
|
}
|
|
|
|
.Ed
|
|
Note that the interrupt handler should
|
|
.Em never
|
|
reduce the priority level. It is automatically called as it had
|
|
raised the interrupt priority to its own level, i.e. further interrupts
|
|
of the same group are being blocked.
|
|
.Sh HISTORY
|
|
The interrupt priority levels appeared in a very early version of
|
|
.Ux .
|
|
They have been traditionally known by number instead of by
|
|
names, and were inclusive up to higher priority levels (i.e., priority
|
|
5 has been blocking everything up to level 5). This is no longer the
|
|
case in
|
|
.Fx .
|
|
The traditional name
|
|
.Ql level
|
|
for them is still reflected in the letter
|
|
.Ql l
|
|
of the respective functions and variables, although they are not
|
|
really levels anymore, but rather different (partially inclusive)
|
|
sets of functions to be blocked during some periods of the life of
|
|
the system. The historical number scheme can be considered as a
|
|
simple linearly ordered set of interrupt priority groups.
|
|
.Sh AUTHORS
|
|
This man page was written by
|
|
.An J\(:org Wunsch .
|