OpenHarmony喂狗源码解读之用户态源码

一、用户代码分析1.程序等待ko加载创建字符设备

WaitAtStartup("/dev/watchdog");
#define WAIT_MAX_COUNT 10
static void WaitAtStartup(const char *source)
{
unsigned int count = 0;
struct stat sourceInfo;
unsigned int waitTime = 500000;
do {
usleep(waitTime);
count++;
} while ((stat(source, &sourceInfo) < 0) && (errno == ENOENT) && (count < WAIT_MAX_COUNT));
if (count == WAIT_MAX_COUNT) {
INIT_LOGE("wait for file:%s failed after %f.", source, WAIT_MAX_COUNT>>1);
}
return;
}

程序起来等待喂狗KO加载创建/dev/watchdog 5s的时间
2.喂狗程序

int interval = 0;
if (argc >= 2) { // Argument nums greater than or equal to 2.
interval = atoi(argv[1]);
}
interval = (interval > 0) ? interval : DEFAULT_INTERVAL;
int gap = 0;
if (argc >= 3) { // Argument nums greater than or equal to 3.
gap = atoi(argv[2]); // 2 second parameter.
}
gap = (gap > 0) ? gap : DEFAULT_GAP;
INIT_LOGI("watchdoge started (interval %d, margin %d), fd = %dn", interval, gap, fd);
// 两个入参之和为用户态喂狗超时时间
int timeoutSet = interval + gap;
int timeoutGet = 0;
int ret = ioctl(fd, WDIOC_SETTIMEOUT, &timeoutSet);
if (ret) {
INIT_LOGE("Failed to set timeout to %dn", timeoutSet);
}
ret = ioctl(fd, WDIOC_GETTIMEOUT, &timeoutGet);
if (ret) {
INIT_LOGE("Failed to get timeoutn");
} else {
// 用户态设置喂狗超时时间为大于gap 用户态喂狗间隔时间为
// 获取内核的超时间 - gap，如果小于gap 用户态喂狗超时时间为1s
interval = (timeoutGet > gap) ? (timeoutGet - gap) : 1;
}
while (1) {
ioctl(fd, WDIOC_KEEPALIVE);
sleep(interval);
}
close(fd);
fd = -1;
return -1;
}

二、喂狗流程

如果用户态设置的喂狗时间超过30s，那么用户态喂狗程序退出不会影响内核线程喂狗，系统不会重启。

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