NAME

timeout - execute a function after a specified length of time

SYNOPSIS

#include <sys/types.h>
#include <sys/conf.h>
timeout_id_t timeout(void (* func)(void *), void *arg,


     clock_t  ticks);

INTERFACE LEVEL

Architecture independent level 1 (DDI/DKI).

PARAMETERS

func

Kernel function to invoke when the time increment expires.

arg

Argument to the function.

ticks

Number of clock ticks to wait before the function is called. Use drv_usectohz(9F) to convert microseconds to clock ticks.

DESCRIPTION

The timeout() function schedules the specified function to be called after a specified time interval. The exact time interval over which the timeout takes effect cannot be guaranteed, but the value given is a close approximation.

The function called by timeout() must adhere to the same restrictions as a driver soft interrupt handler.

The delay(9F) function calls timeout(). Because timeout() is subject to priority inversion, drivers waiting on behalf of processes with real-time constraints should use cv_timedwait(9F) rather than delay().

RETURN VALUES

The timeout() function returns an opaque non-zero timeout identifier that can be passed to untimeout(9F) to cancel the request.

CONTEXT

The timeout() function can be called from user, interrupt, or kernel context.

EXAMPLES

Example 1 Using timeout()

In the following example, the device driver has issued an IO request and is waiting for the device to respond. If the device does not respond within 5 seconds, the device driver will print out an error message to the console.

static void
xxtimeout_handler(void *arg)
{


        struct xxstate *xsp = (struct xxstate *)arg;


        mutex_enter(&xsp->lock);


        cv_signal(&xsp->cv);


        xsp->flags |= TIMED_OUT;


        mutex_exit(&xsp->lock);


        xsp->timeout_id = 0;
}
static uint_t
xxintr(caddr_t arg)
{


        struct xxstate *xsp = (struct xxstate *)arg;


         .


         .


         .


        mutex_enter(&xsp->lock);


        /* Service interrupt */


        cv_signal(&xsp->cv);


        mutex_exit(&xsp->lock);


        if (xsp->timeout_id != 0) {


                (void) untimeout(xsp->timeout_id);


                xsp->timeout_id = 0;


        }


        return(DDI_INTR_CLAIMED);
}
static void
xxcheckcond(struct xxstate *xsp)
{


         .


         .


         .


        xsp->timeout_id = timeout(xxtimeout_handler,


            xsp, (5 * drv_usectohz(1000000)));


        mutex_enter(&xsp->lock);


        while (/* Waiting for interrupt  or timeout*/)


                cv_wait(&xsp->cv, &xsp->lock);


        if (xsp->flags & TIMED_OUT)


                cmn_err(CE_WARN, "Device not responding");


         .


         .


         .


        mutex_exit(&xsp->lock);


         .


         .


         .
}