Langue: en

Version: 306405 (debian - 07/07/09)

Section: 9 (Appels noyau Linux)

BSD mandoc


swi_add swi_sched - register and schedule software interrupt handlers


In sys/param.h In sys/bus.h In sys/interrupt.h Vt extern struct ithd *tty_ithd ; Vt extern struct ithd *clk_ithd ; Vt extern void *net_ih ; Vt extern void *softclock_ih ; Vt extern void *vm_ih ; Ft int Fo swi_add Fa struct ithd **ithdp 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 void Fn swi_sched void *cookie int flags


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.

The Fn swi_add function is used to register a new software interrupt handler. The Fa ithdp argument is an optional pointer to a Vt struct ithd pointer. If this argument points to an existing software interrupt thread, then this handler will be attached to that thread. Otherwise a new thread will be created, and if Fa ithdp is not NULL then the pointer at that address to will be modified to point to the newly created thread. 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 thread 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 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.

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:

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 .

The tty_ithd and clk_ithd variables contain pointers to the software interrupt threads for the tty and clock software interrupts, respectively. tty_ithd is used to hang tty software interrupt handlers off of the same thread. clk_ithd 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 SWI_DELAY The net_ih softclock_ih and vm_ih handler cookies are used to schedule software interrupt threads to run for the networking stack, clock interrupt, and VM subsystem respectively.


The Fn swi_add function returns zero on success and non-zero on failure.


The Fn swi_add function will fail if:
The system-imposed limit on the total number of processes under execution would be exceeded. The limit is given by the sysctl(3) MIB variable KERN_MAXPROC
The Fa flags argument specifies either INTR_ENTROPY or INTR_FAST
The Fa ithdp argument points to a hardware interrupt thread.
Either of the Fa name or Fa handler arguments are NULL
The INTR_EXCL flag is specified and the interrupt thread pointed to by Fa ithdp already has at least one handler, or the interrupt thread already has an exclusive handler.


ithread(9), taskqueue(9)


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 BSD 4.4


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 .