2010.11.24
http://abloz.com
linux中有setitimer等一组函数，但该组函数已经在POSIX.1-2008废弃。现在基于 2.6 版本内核定时器posix替代函数是timer_gettime(2), timer_settime(2)。
接口：
#include <signal.h>
#include <time.h>
int timer_create(clockid_t clockid, struct sigevent *evp,
timer_t *timerid);
int timer_settime(timer_t timerid, int flags,
const struct itimerspec *new_value,
struct itimerspec * old_value);
int timer_gettime(timer_t timerid, struct itimerspec *curr_value);
int timer_getoverrun(timer_t timerid);
int timer_delete(timer_t timerid);
示例：
#include
#define CLOCKID CLOCK_REALTIME
#define SIG SIGRTMIN
#define errExit(msg) do { perror(msg); exit(EXIT_FAILURE);
} while (0)
static void
print_siginfo(siginfo_t *si)
{
timer_t *tidp;
int or;
tidp = si->si_value.sival_ptr;
printf(“ sival_ptr = %p; “, si->si_value.sival_ptr);
printf(“ *sival_ptr = 0x%lxn”, (long) *tidp);
or = timer_getoverrun(*tidp);
if (or == -1)
errExit(“timer_getoverrun”);
else
printf(“ overrun count = %dn”, or);
}
static void
handler(int sig, siginfo_t si, void *uc)
{
/ Note: calling printf() from a signal handler is not
strictly correct, since printf() is not async-signal-safe;
see signal(7) */
printf(“Caught signal %dn”, sig);
print_siginfo(si);
signal(sig, SIG_IGN);
}
int
main(int argc, char *argv[])
{
timer_t timerid;
struct sigevent sev;
struct itimerspec its;
long long freq_nanosecs;
sigset_t mask;
struct sigaction sa;
if (argc != 3) {
fprintf(stderr, “Usage: %s
/* Establish handler for timer signal */
printf(“Establishing handler for signal %dn”, SIG);
sa.sa_flags = SA_SIGINFO;
sa.sa_sigaction = handler;
sigemptyset(&sa.sa_mask);
if (sigaction(SIG, &sa, NULL) == -1)
errExit(“sigaction”);
/* Block timer signal temporarily */
printf(“Blocking signal %dn”, SIG);
sigemptyset(&mask);
sigaddset(&mask, SIG);
if (sigprocmask(SIG_SETMASK, &mask, NULL) == -1)
errExit(“sigprocmask”);
/* Create the timer */
sev.sigev_notify = SIGEV_SIGNAL;
sev.sigev_signo = SIG;
sev.sigev_value.sival_ptr = &timerid;
if (timer_create(CLOCKID, &sev, &timerid) == -1)
errExit(“timer_create”);
printf(“timer ID is 0x%lxn”, (long) timerid);
/* Start the timer */
freq_nanosecs = atoll(argv[2]);
its.it_value.tv_sec = freq_nanosecs / 1000000000;
its.it_value.tv_nsec = freq_nanosecs % 1000000000;
its.it_interval.tv_sec = its.it_value.tv_sec;
its.it_interval.tv_nsec = its.it_value.tv_nsec;
if (timer_settime(timerid, 0, &its, NULL) == -1)
errExit(“timer_settime”);
/* Sleep for a while; meanwhile, the timer may expire
multiple times */
printf(“Sleeping for %d secondsn”, atoi(argv[1]));
sleep(atoi(argv[1]));
/* Unlock the timer signal, so that timer notification
can be delivered */
printf(“Unblocking signal %dn”, SIG);
if (sigprocmask(SIG_UNBLOCK, &mask, NULL) == -1)
errExit(“sigprocmask”);
exit(EXIT_SUCCESS);
}
新版timer支持4种响应类型，sigev_notify参数：
SIGEV_NONE，不异步通知，采用timer_gettime来查询是否超时。
SIGEV_SIGNAL：超时采用信号来进行通知，利用sigaction机制。但由于信号不排队，如果有多个信号，只能保证收到一个信号。
SIGEV_THREAD：定时器到时会创建线程
SIGEV_THREAD_ID（linux特定）：仅推荐用于多线程库
CLOCK_REALTIME 可以看到结果就是从1970年以来所经过的秒数.
将示例文件保存到testtimer.c.编译：
zhouhh@zhh64:~/sms$ gcc -o testtimer -lrt testtimer.c
zhouhh@zhh64:~/sms$ ./testtimer
Usage: ./testtimer
__
参考：
http://www.ibm.com/developerworks/cn/linux/l-cn-timers/
http://www.javaeye.com/topic/309744Technorati
标签: linux, timer
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