Provided by:
freebsd-manpages_6.2-1_all 
NAME
ithread_add_handler, ithread_create, ithread_destroy, ithread_priority,
ithread_remove_handler, ithread_schedule - kernel interrupt threads
SYNOPSIS
#include <sys/param.h>
#include <sys/bus.h>
#include <sys/interrupt.h>
int
ithread_add_handler(struct ithd *ithread, const char *name,
driver_intr_t handler, void *arg, u_char pri,
enum intr_type flags, void **cookiep);
int
ithread_create(struct ithd **ithread, int vector, int flags,
void (*disable)(int), void (*enable)(int), const char *fmt, ...);
int
ithread_destroy(struct ithd *ithread);
u_char
ithread_priority(enum intr_type flags);
int
ithread_remove_handler(void *cookie);
int
ithread_schedule(struct ithd *ithread, int do_switch);
DESCRIPTION
Interrupt threads are kernel threads that run a list of handlers when
triggered by either a hardware or software interrupt. Each interrupt
handler has a name, handler function, handler argument, priority, and
various flags. Each interrupt thread maintains a list of handlers sorted
by priority. This results in higher priority handlers being executed
prior to lower priority handlers. Each thread assumes the priority of
its highest priority handler for its process priority, or PRIO_MAX if it
has no handlers. Interrupt threads are also associated with a single
interrupt source, represented as a vector number.
The ithread_create() function creates a new interrupt thread. The
ithread argument points to an struct ithd pointer that will point to the
newly created thread upon success. The vector argument specifies the
interrupt source to associate this thread with. The flags argument is a
mask of properties of this thread. The only valid flag currently for
ithread_create() is IT_SOFT to specify that this interrupt thread is a
software interrupt. The enable and disable arguments specify optional
functions used to enable and disable this interrupt thread’s interrupt
source. The functions receive the vector corresponding to the thread’s
interrupt source as their only argument. The remaining arguments form a
printf(9) argument list that is used to build the base name of the new
ithread. The full name of an interrupt thread is formed by concatenating
the base name of an interrupt thread with the names of all of its inter‐
rupt handlers.
The ithread_destroy() function destroys a previously created interrupt
thread by releasing its resources and arranging for the backing kernel
thread to terminate. An interrupt thread can only be destroyed if it has
no handlers remaining.
The ithread_add_handler() function adds a new handler to an existing
interrupt thread specified by ithread. The name argument specifies a
name for this handler. The handler and arg arguments provide the func‐
tion to execute for this handler and an argument to pass to it. The pri
argument specifies the priority of this handler and is used both in sort‐
ing it in relation to the other handlers for this thread and to specify
the priority of the backing kernel thread. The flags argument can be
used to specify properties of this handler as defined in If cookiep is
not NULL, then it will be assigned a cookie that can be used later to
remove this handler.
The ithread_remove_handler() removes a handler from an interrupt thread.
The cookie argument specifies the handler to remove from its thread.
The ithread_schedule() function schedules an interrupt thread to run. If
the do_switch argument is non-zero and the interrupt thread is idle, then
a context switch will be forced after putting the interrupt thread on the
run queue.
The ithread_priority() function translates the INTR_TYPE_* interrupt
flags into interrupt handler priorities.
The interrupt flags not related to the type of a particular interrupt
(INTR_TYPE_*) can be used to specify additional properties of both hard‐
ware and software interrupt handlers. The INTR_EXCL flag specifies that
this handler cannot share an interrupt thread with another handler. The
INTR_FAST flag specifies that when this handler is executed, it should be
run immediately rather than being run asynchronously when its interrupt
thread is scheduled to run. The INTR_FAST flag implies INTR_EXCL. The
INTR_MPSAFE flag specifies that this handler is MP safe in that it does
not need the Giant mutex to be held while it is executed. The
INTR_ENTROPY flag specifies that the interrupt source this handler is
tied to is a good source of entropy, and thus that entropy should be
gathered when an interrupt from the handler’s source triggers.
Presently, the INTR_FAST and INTR_ENTROPY flags are not valid for soft‐
ware interrupt handlers.
The ithread_add_handler(), ithread_create(), ithread_destroy(),
ithread_remove_handler(), and ithread_schedule() functions return zero on
success and non-zero on failure. The ithread_priority() function returns
a process priority corresponding to the passed in interrupt flags.
EXAMPLES
The swi_add() function demonstrates the use of ithread_create() and
ithread_add_handler().
int
swi_add(struct ithd **ithdp, const char *name, driver_intr_t handler,
void *arg, int pri, enum intr_type flags, void **cookiep)
{
struct proc *p;
struct ithd *ithd;
int error;
if (flags & (INTR_FAST | INTR_ENTROPY))
return (EINVAL);
ithd = (ithdp != NULL) ? *ithdp : NULL;
if (ithd != NULL) {
if ((ithd->it_flags & IT_SOFT) == 0)
return(EINVAL);
} else {
error = ithread_create(&ithd, pri, IT_SOFT, NULL, NULL,
"swi%d:", pri);
if (error)
return (error);
if (ithdp != NULL)
*ithdp = ithd;
}
return (ithread_add_handler(ithd, name, handler, arg, pri + PI_SOFT,
flags, cookiep));
}
ERRORS
The ithread_add_handler() function will fail if:
[EINVAL] Any of the ithread, handler, or name arguments are
NULL.
[EINVAL] The INTR_EXCL flag is specified and the interrupt
thread ithread already has at least one handler, or
the interrupt thread ithread already has an exclusive
handler.
[ENOMEM] Could not allocate needed memory for this handler.
The ithread_create() function will fail if:
[EAGAIN] The system-imposed limit on the total number of pro‐
cesses under execution would be exceeded. The limit
is given by the sysctl(3) MIB variable KERN_MAXPROC.
[EINVAL] A flag other than IT_SOFT was specified in the flags
parameter.
[ENOMEM] Could not allocate needed memory for this interrupt
thread.
The ithread_destroy() function will fail if:
[EINVAL] The ithread argument is NULL.
[EINVAL] The interrupt thread pointed to by ithread has at
least one handler.
The ithread_remove_handler() function will fail if:
[EINVAL] The cookie argument is NULL.
The ithread_schedule() function will fail if:
[EINVAL] The ithread argument is NULL.
[EINVAL] The interrupt thread pointed to by ithread has no
interrupt handlers.
kthread(9), swi(9)
HISTORY
Interrupt threads and their corresponding API first appeared in
FreeBSD 5.0.
BUGS
Currently struct ithd represents both an interrupt source and an inter‐
rupt thread. There should be a separate struct isrc that contains a vec‐
tor number, enable and disable functions, etc. that an ithread holds a
reference to.