NAME
ipi —
MI IPI interface
SYNOPSIS
#include <sys/ipi.h>
typedef void (*ipi_func_t)(void *);
u_int
ipi_register(
ipi_func_t
func,
void *arg);
void
ipi_unregister(
u_int
ipi_id);
void
ipi_trigger(
u_int
ipi_id,
struct cpu_info
*ci);
void
ipi_unicast(
ipi_msg_t
*msg,
struct cpu_info
*ci);
void
ipi_multicast(
ipi_msg_t
*msg,
const kcpuset_t
*target);
void
ipi_broadcast(
ipi_msg_t
*msg);
void
ipi_wait(
ipi_msg_t
*msg);
DESCRIPTION
The machine-independent
ipi interface provides capability to
send inter-processor interrupts (IPIs) amongst CPUs. The interface has two
mechanisms: asynchronous IPI to invoke functions with a constant argument and
synchronous IPIs with the cross-call support.
Other synchronization interfaces are built using the MI IPI interface. For a
general purpose inter-processor cross-calls or remote interrupts, use the
xcall(9) or
softint(9) interfaces.
The primary use cases of the MI IPIs include the following:
- provide a facility for the
softint(9) subsystem to
schedule software interrupts on remote CPUs
- provide a facility for the
xcall(9) subsystem
- abstract IPI handling and
facilitate machine-dependent code
Asynchronous IPI interface
This interface allows dynamic registration of IPI handlers with a constant
argument and asynchronous triggering of interrupts.
-
-
- ipi_register(func,
arg)
- Register an IPI handler func with an
arbitrary argument arg. Returns a non-zero IPI
identifier on success and zero on failure.
-
-
- ipi_unregister(ipi_id)
- Unregister the IPI handler identified by the
ipi_id.
-
-
- ipi_trigger(ipi_id,
ci)
- Trigger an IPI identified by ipi_id
on a remote CPU specified by ci. This function must
be called with the kernel preemption disabled and the target CPU must be
remote.
Synchronous IPI interface
This interface provides capability to perform cross-calls, i.e. invoke an
arbitrary function on a remote CPU. The invocations are performed
synchronously and the caller must wait for completion. The cross-call is
described by an IPI "message". The caller has to fill in an
ipi_msg_t structure which has the following public
members:
ipi_func_t func;
void arg;
The
func member specifies a function to invoke and
arg is the argument to be passed to the function.
-
-
- ipi_unicast(msg,
ci)
- Send an IPI to a remote CPU specified by
ci.
-
-
- ipi_multicast(msg,
target)
- Send IPIs to a CPU set specified by
target.
-
-
- ipi_broadcast(msg)
- Send IPIs to all CPUs.
-
-
- ipi_wait(msg)
- Wait until all IPIs complete.
All described functions, except
ipi_wait(), must be called
with the kernel preemption disabled. All synchronous IPI invocations must be
completed (wait for them with the
ipi_wait() function)
before the IPI message structure can be destroyed or new cross-call requests
can be performed.
NOTES
Functions being called must be lightweight. They run at
IPL_HIGH
and should generally not use any other
synchronization interfaces such as
mutex(9). If spin-locks are used,
they must be used carefully and have no contention.
CODE REFERENCES
The
ipi interface is implemented within the file
sys/kern/subr_ipi.c.
SEE ALSO
kcpuset(9),
kpreempt(9),
softint(9),
spl(9),
xcall(9)
HISTORY
The
ipi interface first appeared in
NetBSD
7.0.
AUTHORS
Mindaugas Rasiukevicius
<
rmind@NetBSD.org>