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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"
71 .Sy This API is deprecated.
72 .Sy Use mutexes to protect data structures instead.
75 .Sy for more information.
79 function family sets the interrupt priority
82 This prevents interrupt handlers of the blocked priority level from
83 being run. This is used in the
85 part of a driver (the part that runs on behalf of the user process) to
86 examine or modify data areas that might be examined or modified by
89 Each driver that uses interrupts is normally assigned to an interrupt
90 priority group by a keyword in its config line.
92 .Bd -literal -offset indent
93 device foo0 at isa? port 0x0815 irq 12 tty
96 assigns interrupt 12 to the
98 priority group. The system automatically arranges for interrupts in
101 group to be called at a priority >=
107 sets the interrupt priority to an absolute value. The intent is that
108 the value returned by the other functions should be saved in a local
109 variable, and later passed to
111 in order to restore the previous priority.
115 lowers the priority to a value where all interrupt handlers are
116 unblocked, but ASTs (asynchronous system traps) remain blocked until
117 the system is about to return to user mode.
119 The traditional assignment of the various device drivers to the
120 interrupt priority groups can be roughly classified as:
121 .Bl -tag -width Fn splnet
123 All network interface drivers.
127 (i.e., disk and the like) drivers.
129 Basically, all non-network communications devices, but effectively
130 used for all drivers that are neither network nor disks.
137 return the previous priority value.
139 This is a typical example demonstrating the usage:
152 struct foo_softc *sc;
157 if (!(sc->flags & FOO_READY)) {
158 /* Not ready, must sleep on resource. */
159 sc->flags |= FOO_ASLEEP;
160 error = tsleep(sc, PZERO, "foordy", 0);
161 sc->flags &= ~FOO_ASLEEP;
163 sc->flags &= ~FOO_READY;
172 struct foo_softc *sc;
175 sc->flags |= FOO_READY;
176 if (sc->flags & FOO_ASLEEP)
177 /* Somebody was waiting for us, awake him. */
183 Note that the interrupt handler should
185 reduce the priority level. It is automatically called as it had
186 raised the interrupt priority to its own level, i.e. further interrupts
187 of the same group are being blocked.
189 The interrupt priority levels appeared in a very early version of
190 Unix. They have been traditionally known by number instead of by
191 names, and were inclusive up to higher priority levels (i.e., priority
192 5 has been blocking everything up to level 5). This is no longer the
197 for them is still reflected in the letter
199 of the respective functions and variables, although they are not
200 really levels anymore, but rather different (partially inclusive)
201 sets of functions to be blocked during some periods of the life of
202 the system. The historical number scheme can be considered as a
203 simple linearly ordered set of interrupt priority groups.
205 This man page was written by