.\" Copyright (c) 2000-2001 John H. Baldwin .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" $FreeBSD$ .\" .Dd April 19, 2012 .Dt SWI 9 .Os .Sh NAME .Nm swi_add , .Nm swi_remove , .Nm swi_sched .Nd register and schedule software interrupt handlers .Sh SYNOPSIS .In sys/param.h .In sys/bus.h .In sys/interrupt.h .Vt "extern struct intr_event *tty_intr_event" ; .Vt "extern struct intr_event *clk_intr_event" ; .Vt "extern void *vm_ih" ; .Ft int .Fo swi_add .Fa "struct intr_event **eventp" .Fa "const char *name" .Fa "driver_intr_t handler" .Fa "void *arg" .Fa "int pri" .Fa "enum intr_type flags" .Fa "void **cookiep" .Fc .Ft int .Fn swi_remove "void *cookie" .Ft void .Fn swi_sched "void *cookie" "int flags" .Sh DESCRIPTION These functions are used to register and schedule software interrupt handlers. Software interrupt handlers are attached to a software interrupt thread, just as hardware interrupt handlers are attached to a hardware interrupt thread. Multiple handlers can be attached to the same thread. Software interrupt handlers can be used to queue up less critical processing inside of hardware interrupt handlers so that the work can be done at a later time. Software interrupt threads are different from other kernel threads in that they are treated as an interrupt thread. This means that time spent executing these threads is counted as interrupt time, and that they can be run via a lightweight context switch. .Pp The .Fn swi_add function is used to add a new software interrupt handler to a specified interrupt event. The .Fa eventp argument is an optional pointer to a .Vt struct intr_event pointer. If this argument points to an existing event that holds a list of interrupt handlers, then this handler will be attached to that event. Otherwise a new event will be created, and if .Fa eventp is not .Dv NULL , then the pointer at that address to will be modified to point to the newly created event. The .Fa name argument is used to associate a name with a specific handler. This name is appended to the name of the software interrupt thread that this handler is attached to. The .Fa handler argument is the function that will be executed when the handler is scheduled to run. The .Fa arg parameter will be passed in as the only parameter to .Fa handler when the function is executed. The .Fa pri value specifies the priority of this interrupt handler relative to other software interrupt handlers. If an interrupt event is created, then this value is used as the vector, and the .Fa flags argument is used to specify the attributes of a handler such as .Dv INTR_MPSAFE . The .Fa cookiep argument points to a .Vt void * cookie. This cookie will be set to a value that uniquely identifies this handler, and is used to schedule the handler for execution later on. .Pp The .Fn swi_remove function is used to teardown an interrupt handler pointed to by the .Fa cookie argument. It detaches the interrupt handler from the associated interrupt event and frees its memory. .Pp The .Fn swi_sched function is used to schedule an interrupt handler and its associated thread to run. The .Fa cookie argument specifies which software interrupt handler should be scheduled to run. The .Fa flags argument specifies how and when the handler should be run and is a mask of one or more of the following flags: .Bl -tag -width SWI_DELAY .It Dv SWI_DELAY Specifies that the kernel should mark the specified handler as needing to run, but the kernel should not schedule the software interrupt thread to run. Instead, .Fa handler will be executed the next time that the software interrupt thread runs after being scheduled by another event. Attaching a handler to the clock software interrupt thread and using this flag when scheduling a software interrupt handler can be used to implement the functionality performed by .Fn setdelayed in earlier versions of .Fx . .El .Pp The .Va tty_intr_event and .Va clk_intr_event variables contain pointers to the software interrupt handlers for the tty and clock software interrupts, respectively. .Va tty_intr_event is used to hang tty software interrupt handlers off of the same thread. .Va clk_intr_event is used to hang delayed handlers off of the clock software interrupt thread so that the functionality of .Fn setdelayed can be obtained in conjunction with .Dv SWI_DELAY . The .Va vm_ih handler cookie is used to schedule software interrupt threads to run for the VM subsystem. .Sh RETURN VALUES The .Fn swi_add and .Fn swi_remove functions return zero on success and non-zero on failure. .Sh ERRORS The .Fn swi_add function will fail if: .Bl -tag -width Er .It Bq Er EAGAIN The system-imposed limit on the total number of processes under execution would be exceeded. The limit is given by the .Xr sysctl 3 MIB variable .Dv KERN_MAXPROC . .It Bq Er EINVAL The .Fa flags argument specifies .Dv INTR_ENTROPY . .It Bq Er EINVAL The .Fa eventp argument points to a hardware interrupt thread. .It Bq Er EINVAL Either of the .Fa name or .Fa handler arguments are .Dv NULL . .It Bq Er EINVAL The .Dv INTR_EXCL flag is specified and the interrupt event pointed to by .Fa eventp already has at least one handler, or the interrupt event already has an exclusive handler. .El .Pp The .Fn swi_remove function will fail if: .Bl -tag -width Er .It Bq Er EINVAL A software interrupt handler pointed to by .Fa cookie is .Dv NULL . .El .Sh SEE ALSO .Xr ithread 9 , .Xr taskqueue 9 .Sh HISTORY The .Fn swi_add and .Fn swi_sched functions first appeared in .Fx 5.0 . They replaced the .Fn register_swi function which appeared in .Fx 3.0 and the .Fn setsoft* , and .Fn schedsoft* functions which date back to at least .Bx 4.4 . The .Fn swi_remove function first appeared in .Fx 6.1 . .Sh BUGS Most of the global variables described in this manual page should not be global, or at the very least should not be declared in .In sys/interrupt.h .