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

ddi_periodic_delete - cancel periodic function invocation requests

#include <sys/dditypes.h>
#include <sys/sunddi.h>
void ddi_periodic_delete(ddi_periodic_t request);

illumos DDI specific (illumos DDI)

request
ddi_periodic_t opaque value returned by ddi_periodic_add(9F)

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_periodic_delete() returns.

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

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);
}

cv_timedwait(9F), ddi_intr_get_pri(9F), ddi_periodic_add(9F), qtimeout(9F), quntimeout(9F), timeout(9F), untimeout(9F)

Historically this interface was advertised as safe for use from within the periodic callback function. In order to ensure the correct operation of the system, and as reflected in the documentation above, this unlikely (and unsafe) usage pattern is no longer allowed.
February 12, 2014 OmniOS