201 lines
6.0 KiB
Groff
201 lines
6.0 KiB
Groff
.\" $NetBSD: ipi.9,v 1.4 2019/04/06 07:57:04 wiz Exp $
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.\"
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.\" Copyright (c) 2014, 2019 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Mindaugas Rasiukevicius.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd March 31, 2019
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.Dt IPI 9
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.Os
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.Sh NAME
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.Nm ipi
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.Nd MI IPI interface
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.Sh SYNOPSIS
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.In sys/ipi.h
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.Vt typedef void (*ipi_func_t)(void *);
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.\" -----
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.Ft u_int
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.Fn ipi_register "ipi_func_t func" "void *arg"
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.Ft void
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.Fn ipi_unregister "u_int ipi_id"
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.Ft void
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.Fn ipi_trigger "u_int ipi_id" "struct cpu_info *ci"
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.Ft void
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.Fn ipi_trigger_multi "u_int ipi_id" "const kcpuset_t *target"
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.Ft void
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.Fn ipi_trigger_broadcast "u_int ipi_id" "bool skip_self"
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.\" -----
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.Ft void
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.Fn ipi_unicast "ipi_msg_t *msg" "struct cpu_info *ci"
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.Ft void
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.Fn ipi_multicast "ipi_msg_t *msg" "const kcpuset_t *target"
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.Ft void
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.Fn ipi_broadcast "ipi_msg_t *msg" "bool skip_self"
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.Ft void
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.Fn ipi_wait "ipi_msg_t *msg"
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.\" -----
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.Sh DESCRIPTION
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The machine-independent
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.Nm
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interface provides capability to send inter-processor interrupts (IPIs)
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amongst CPUs.
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The interface has two mechanisms: asynchronous IPI to invoke functions
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with a constant argument and synchronous IPIs with the cross-call support.
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.Pp
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Other synchronization interfaces are built using the MI IPI interface.
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For a general purpose inter-processor cross-calls or remote
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interrupts, use the
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.Xr xcall 9
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or
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.Xr softint 9
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interfaces.
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.Pp
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The primary use cases of the MI IPIs include the following:
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.Bl -hyphen -compact
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.It
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provide a facility for the
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.Xr softint 9
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subsystem to schedule software interrupts on remote CPUs
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.It
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provide a facility for the
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.Xr xcall 9
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subsystem
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.It
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abstract IPI handling and facilitate machine-dependent code
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.El
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.\" -----
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.Ss Asynchronous IPI interface
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This interface allows dynamic registration of IPI handlers with a constant
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argument and asynchronous triggering of interrupts.
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.Bl -tag -width compact
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.It Fn ipi_register "func" "arg"
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Register an IPI handler
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.Fa func
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with an arbitrary argument
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.Fa arg .
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Returns a non-zero IPI identifier on success and zero on failure.
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.It Fn ipi_unregister "ipi_id"
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Unregister the IPI handler identified by the
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.Fa ipi_id .
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.It Fn ipi_trigger "ipi_id" "ci"
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Trigger an IPI identified by
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.Fa ipi_id
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on a remote CPU specified by
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.Fa ci .
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This function must be called with kernel preemption disabled and
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the target CPU must be remote.
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.It Fn ipi_trigger_multi "ipi_id" "target"
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Trigger an IPI identified by
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.Fa ipi_id
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on all of the CPUs in the set specified by
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.Fa target .
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This function must be called with kernel preemption disabled.
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The sending CPU may be included in the CPU set; when this is the case,
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the IPI on the sending CPU is processes synchronously.
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.It Fn ipi_trigger_broadcast "ipi_id" "skip_self"
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Trigger an IPI identified by
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.Fa ipi_id
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on all of the attached CPUs.
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This function must be called with kernel preemption disabled.
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Optionally, the sending CPU may be skipped by passing
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.Dv true
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for
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.Fa skip_self .
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.El
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.\" -----
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.Ss Synchronous IPI interface
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This interface provides capability to perform cross-calls, i.e. invoke
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an arbitrary function on a remote CPU.
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The invocations are performed synchronously and the caller must wait
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for completion.
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The cross-call is described by an IPI "message".
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The caller has to fill in an
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.Vt ipi_msg_t
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structure which has the following public members:
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.Bd -literal
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ipi_func_t func;
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void arg;
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.Ed
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.Pp
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The
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.Ar func
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member specifies a function to invoke and
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.Ar arg
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is the argument to be passed to the function.
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.Bl -tag -width compact
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.It Fn ipi_unicast "msg" "ci"
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Send an IPI to a remote CPU specified by
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.Fa ci .
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.It Fn ipi_multicast "msg" "target"
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Send IPIs to a CPU set specified by
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.Fa target .
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.It Fn ipi_broadcast "msg" "skip_self"
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Send IPIs to all CPUs.
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Optionally, the sending CPU may be skipped by passing
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.Dv true
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for
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.Fa skip_self .
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.It Fn ipi_wait "msg"
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Wait until all IPIs complete.
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.El
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.Pp
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All described functions, except
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.Fn ipi_wait ,
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must be called with the kernel preemption disabled.
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All synchronous IPI invocations must be completed (wait for them with the
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.Fn ipi_wait
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function) before the IPI message structure can be destroyed or new
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cross-call requests can be performed.
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.\" -----
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.Sh NOTES
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Functions being called must be lightweight.
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They run at
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.Dv IPL_HIGH
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and should generally not use any other synchronization interfaces
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such as
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.Xr mutex 9 .
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If spin-locks are used, they must be used carefully and have no contention.
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.\" -----
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.Sh CODE REFERENCES
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The
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.Nm
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interface is implemented within the file
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.Pa sys/kern/subr_ipi.c .
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.\" -----
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.Sh SEE ALSO
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.Xr kcpuset 9 ,
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.Xr kpreempt 9 ,
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.Xr softint 9 ,
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.Xr spl 9 ,
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.Xr xcall 9
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.Sh HISTORY
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The
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.Nm
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interface first appeared in
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.Nx 7.0 .
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.Sh AUTHORS
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.An Mindaugas Rasiukevicius Aq Mt rmind@NetBSD.org
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