ddi_periodic_delete man page on SmartOS

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DDI_PERIODIC_DELETE(9F)				       DDI_PERIODIC_DELETE(9F)

NAME
       ddi_periodic_delete - cancel periodic function invocation requests

SYNOPSIS
       #include <sys/dditypes.h>
       #include <sys/sunddi.h>

       void ddi_periodic_delete(ddi_periodic_t request);

INTERFACE LEVEL
       Solaris DDI specific (Solaris DDI)

PARAMETERS
       request
	      ddi_periodic_t opaque value returned by ddi_periodic_add(9F)

DESCRIPTION
       The   ddi_periodic_delete()  function  cancels  a  periodic  invocation
       request previously established with ddi_periodic_add(9F).

       It is not possible to cancel a periodic invocation request from	within
       the periodic callback itself; to do so is a programming error that will
       panic the system.  Instead, requests must be cancelled from some	 other
       user or kernel context routine, such as the detach(9E) entry point of a
       module.

       If the callback function is already executing (for instance, on another
       CPU)  when  the	request is cancelled, ddi_periodic_delete() will block
       until it finishes executing and is completely unregistered.  Because of
       this,  locks  acquired by the callback function must not be held across
       the call to ddi_periodic_delete() or a deadlock may result.

       The callback will not be invoked again  after  the  call	 to  ddi_peri‐
       odic_delete() returns.

CONTEXT
       The  ddi_periodic_delete()  function  may be called from user or kernel
       context.

EXAMPLES
       Example 1 Cancelling a periodic invocation request

       In the following example, the device  driver  cancels  the  request  by
       calling ddi_periodic_delete() and passing the opaque request identifier
       returned by a previous call to ddi_periodic_add(9F).

	 /*
	  * Stop the periodic timer.
	  */
	 static void
	 stop_periodic_timer(struct my_state *statep)
	 {
		 ddi_periodic_delete(statep->periodic_id);
		 mutex_destroy(&statep->lock);
	 }

	 static void
	 start_periodic_timer(struct my_state *statep)
	 {
		 hrtime_t interval = CHECK_INTERVAL;

		 mutex_init(&statep->lock, NULL, MUTEX_DRIVER, DDI_IPL_0);

		 /*
		  * Register my_callback which is invoked periodically
		  * in CHECK_INTERVAL in kernel context.
		  */
		 statep->periodic_id = ddi_periodic_add(my_periodic_func,
		     statep, interval, DDI_IPL_0);
	 }

	 static void
	 my_periodic_func(void *arg)
	 {
		 /*
		  * This handler is invoked periodically.
		  */
		 struct my_state *statep = (struct my_state *)arg;

		 mutex_enter(&statep->lock);
		 if (load_unbalanced(statep)) {
			 balance_tasks(statep);
		 }
		 mutex_exit(&statep->lock);
	 }

SEE ALSO
       cv_timedwait(9F),  ddi_intr_get_pri(9F),	 ddi_periodic_add(9F),	qtime‐
       out(9F), quntimeout(9F), timeout(9F), untimeout(9F)

NOTES
       Historically  this interface was advertised as safe for use from within
       the periodic callback function.	In order to ensure the correct	opera‐
       tion  of	 the system, and as reflected in the documentation above, this
       unlikely (and unsafe) usage pattern is no longer allowed.

				 Feb 12, 2014	       DDI_PERIODIC_DELETE(9F)
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