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untimeout(9f)

untimeout(9F)                  Kernel Functions                  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
       The untimeout() function cancels a pending timeout(9F) request. untime‐
       out()  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.  Dri‐
       vers  should  be  structured with the understanding that the arrival of
       both an interrupt and a timeout for that interrupt can occasionally oc‐
       cur, in either order.

RETURN VALUES
       The untimeout() function returns -1 if the id is not found  or  if  the
       timeout handler calls this function on itself. Otherwise, it returns an
       integer value greater than or equal to 0.

CONTEXT
       The  untimeout() function can be called from user, interrupt, or kernel
       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 re‐
       spond within 5 seconds, the device driver will print out an error  mes‐
       sage 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 in Oracle Solaris 11.4

Oracle Solaris 11.4               20 Sep 2012                    untimeout(9F)
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