w_start Kernel Service

Purpose

Starts a watchdog timer.

Syntax

#include <sys/types.h>
#include <sys/errno.h>
#include <sys/watchdog.h>

void w_start (w)
struct watchdog *w;

Parameter

Description

The watchdog timers, including the w_start kernel service, are typically used to verify that an I/O operation completes in a reasonable time. The w_start and w_stop kernel services are designed to allow the timer to be started and stopped efficiently. The kernel decrements the w->count watchdog count every second. The kernel calls the w->func watchdog timer function when the w->count watchdog count reaches 0. A watchdog timer is ignored when the w->count watchdog count is less than or equal to 0.

The w_start kernel service sets the w->count watchdog count to a value of w->restart.

Attention: The watchdog structure must be pinned when the w_start kernel service is called. It must remain pinned until after the call to the w_clear kernel service. During this time, the watchdog structure must not be altered except by the watchdog services.

Execution Environment

The w_start kernel service can be called from the process and interrupt environments.

Return Values

The w_start kernel service has no return values.

Implementation Specifics

The w_start kernel service is part of Base Operating System (BOS) Runtime.

Related Information

The w_clear kernel service, w_init kernel service, w_stop kernel service.

Timer and Time-of-Day Kernel Services in AIX Kernel Extensions and Device Support Programming Concepts.