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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Kernel Functions for Drivers

timeout(9F)

INTERFACE LEVEL
PARAMETERS
DESCRIPTION
RETURN VALUES
CONTEXT
EXAMPLES
SEE ALSO

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.

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 function called by timeout() is run in interrupt context and must not sleep or call other functions that might sleep.

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

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

CONTEXT

timeout() can be called from user or interrupt 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); . . . }