Tribblix: manual page: timeout.9f

TIMEOUT(9F) Kernel Functions for Drivers TIMEOUT(9F)

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);
.
.
.
}