timeout(9f) [opensolaris man page]

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);
		  .
		  .
		  .
	 }

SEE ALSO

       bufcall(9F), cv_timedwait(9F), ddi_in_panic(9F), delay(9F), drv_usectohz(9F), untimeout(9F)

       Writing Device Drivers

SunOS 5.11							    16 Jan 2006 						       timeout(9F)

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

NAME

       untimeout - cancel previous timeout function call

SYNOPSIS

       #include <sys/types.h>
       #include <sys/conf.h>

       clock_t untimeout(timeout_id_t id);

INTERFACE LEVEL

       Architecture independent level 1 (DDI/DKI).

PARAMETERS

       id	Opaque timeout ID from a previous timeout(9F) call.

DESCRIPTION

       untimeout() cancels a pending  timeout(9F) request. untimeout() will not return until the pending callback is cancelled or has run. Because
       of this, locks acquired by the callback routine should not be held across the call to untimeout() or a deadlock may result.

       Since no mutex should be held across the call to untimeout(), there is a race condition between the occurrence of an expected event and the
       execution  of  the  timeout  handler. In particular, it should be noted that no problems will result from calling untimeout() for a timeout
       which is either running on another CPU, or has already completed.  Drivers should be structured with the understanding that the arrival	of
       both an interrupt and a timeout for that interrupt can occasionally occur, in either order.

RETURN VALUES

       untimeout() returns -1 if the id is not found. Otherwise, it returns an integer value greater than or equal to 0.

CONTEXT

       untimeout() can be called from user or interrupt context.

EXAMPLES

       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);
		.
		.
		.
       }

SEE ALSO

       open(9E), cv_signal(9F), cv_wait_sig(9F), delay(9F), timeout(9F)

       Writing Device Drivers

SunOS 5.10							    18 Feb 1998 						     untimeout(9F)