untimeout(9F)

NAME

untimeout − cancel previous timeout function call

SYNOPSIS

#include <sys/types.h>
#include <sys/conf.h>
int untimeout(int id);

INTERFACE LEVEL

Architecture independent level 1 (DDI/DKI).

ARGUMENTS

id Identification value generated by a previous timeout(9F) function 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(caddr_t 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 u_int
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,
            (caddr_t)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);
         .
         .
         .
}

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