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44 .Nd manipulate interrupt priorities
46 .Fd #include <sys/types.h>
47 .Fd #include <sys/systm.h>
59 .Fn splsoftclock "void"
63 .Fn splstatclock "void"
69 .Fn splx "intrmask_t ipl"
72 This API is deprecated.
73 Use mutexes to protect data structures instead.
81 function family sets the interrupt priority
84 This prevents interrupt handlers of the blocked priority level from
85 being run. This is used in the
87 part of a driver (the part that runs on behalf of the user process) to
88 examine or modify data areas that might be examined or modified by
91 Each driver that uses interrupts is normally assigned to an interrupt
92 priority group by a keyword in its config line.
94 .Bd -literal -offset indent
95 device foo0 at isa? port 0x0815 irq 12 tty
98 assigns interrupt 12 to the
100 priority group. The system automatically arranges for interrupts in
103 group to be called at a priority >=
109 sets the interrupt priority to an absolute value. The intent is that
110 the value returned by the other functions should be saved in a local
111 variable, and later passed to
113 in order to restore the previous priority.
117 lowers the priority to a value where all interrupt handlers are
118 unblocked, but ASTs (asynchronous system traps) remain blocked until
119 the system is about to return to user mode.
121 The traditional assignment of the various device drivers to the
122 interrupt priority groups can be roughly classified as:
125 All network interface drivers.
129 (i.e., disk and the like) drivers.
131 Basically, all non-network communications devices, but effectively
132 used for all drivers that are neither network nor disks.
139 return the previous priority value.
141 This is a typical example demonstrating the usage:
154 struct foo_softc *sc;
159 if (!(sc->flags & FOO_READY)) {
160 /* Not ready, must sleep on resource. */
161 sc->flags |= FOO_ASLEEP;
162 error = tsleep(sc, PZERO, "foordy", 0);
163 sc->flags &= ~FOO_ASLEEP;
165 sc->flags &= ~FOO_READY;
174 struct foo_softc *sc;
177 sc->flags |= FOO_READY;
178 if (sc->flags & FOO_ASLEEP)
179 /* Somebody was waiting for us, awake him. */
185 Note that the interrupt handler should
187 reduce the priority level. It is automatically called as it had
188 raised the interrupt priority to its own level, i.e. further interrupts
189 of the same group are being blocked.
191 The interrupt priority levels appeared in a very early version of
192 Unix. They have been traditionally known by number instead of by
193 names, and were inclusive up to higher priority levels (i.e., priority
194 5 has been blocking everything up to level 5). This is no longer the
199 for them is still reflected in the letter
201 of the respective functions and variables, although they are not
202 really levels anymore, but rather different (partially inclusive)
203 sets of functions to be blocked during some periods of the life of
204 the system. The historical number scheme can be considered as a
205 simple linearly ordered set of interrupt priority groups.
207 This man page was written by