sunos man page for untimeout

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)