2 .\" Copyright (c) 1996 Joerg Wunsch
4 .\" All rights reserved.
6 .\" Redistribution and use in source and binary forms, with or without
7 .\" modification, are permitted provided that the following conditions
9 .\" 1. Redistributions of source code must retain the above copyright
10 .\" notice, this list of conditions and the following disclaimer.
11 .\" 2. Redistributions in binary form must reproduce the above copyright
12 .\" notice, this list of conditions and the following disclaimer in the
13 .\" documentation and/or other materials provided with the distribution.
15 .\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
16 .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 .\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
19 .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 .\" $FreeBSD: src/share/man/man9/spl.9,v 1.8.2.5 2001/12/17 11:30:19 ru Exp $
44 .Nd manipulate interrupt priorities
59 .Fn splsoftclock "void"
63 .Fn splstatclock "void"
69 .Fn splx "intrmask_t ipl"
73 function family sets the interrupt priority
76 This prevents interrupt handlers of the blocked priority level from
77 being run. This is used in the
79 part of a driver (the part that runs on behalf of the user process) to
80 examine or modify data areas that might be examined or modified by
83 Each driver that uses interrupts is normally assigned to an interrupt
84 priority group by a keyword in its config line.
86 .Bd -literal -offset indent
87 device foo0 at isa? port 0x0815 irq 12 tty
90 assigns interrupt 12 to the
92 priority group. The system automatically arranges for interrupts in
95 group to be called at a priority >=
101 sets the interrupt priority to an absolute value. The intent is that
102 the value returned by the other functions should be saved in a local
103 variable, and later passed to
105 in order to restore the previous priority.
109 lowers the priority to a value where all interrupt handlers are
110 unblocked, but ASTs (asynchronous system traps) remain blocked until
111 the system is about to return to user mode.
113 The traditional assignment of the various device drivers to the
114 interrupt priority groups can be roughly classified as:
117 All network interface drivers.
121 (i.e., disk and the like) drivers.
123 Basically, all non-network communications devices, but effectively
124 used for all drivers that are neither network nor disks.
131 return the previous priority value.
133 This is a typical example demonstrating the usage:
146 struct foo_softc *sc;
151 if (!(sc->flags & FOO_READY)) {
152 /* Not ready, must sleep on resource. */
153 sc->flags |= FOO_ASLEEP;
154 error = tsleep(sc, PZERO, "foordy", 0);
155 sc->flags &= ~FOO_ASLEEP;
157 sc->flags &= ~FOO_READY;
166 struct foo_softc *sc;
169 sc->flags |= FOO_READY;
170 if (sc->flags & FOO_ASLEEP)
171 /* Somebody was waiting for us, awake him. */
177 Note that the interrupt handler should
179 reduce the priority level. It is automatically called as it had
180 raised the interrupt priority to its own level, i.e. further interrupts
181 of the same group are being blocked.
183 The interrupt priority levels appeared in a very early version of
184 Unix. They have been traditionally known by number instead of by
185 names, and were inclusive up to higher priority levels (i.e., priority
186 5 has been blocking everything up to level 5). This is no longer the
191 for them is still reflected in the letter
193 of the respective functions and variables, although they are not
194 really levels anymore, but rather different (partially inclusive)
195 sets of functions to be blocked during some periods of the life of
196 the system. The historical number scheme can be considered as a
197 simple linearly ordered set of interrupt priority groups.
199 This man page was written by