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我在程序的主要功能中創建了一個POSIX計時器。主程序的每個線程都設置計時器,以便在其到期時,信號處理程序更新一個變量,以喚醒同一進程的下一個線程。POSIX計時器在幾次運行後掛起
計時器在大多數情況下工作正常,但並非總是如此。它有時在其他運行中完成完整的執行,它會掛起。可能的原因是什麼?我的懷疑與信號傳遞有關。
下面是代碼:
#define _GNU_SOURCE
#define _POSIX_C_SOURCE 199309
#include <sched.h>
#include <unistd.h>
#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>
#include <semaphore.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <syscall.h>
#define NUM_THREADS 10
#define CLOCKID CLOCK_REALTIME
#define SIG SIGUSR1
int ret;
timer_t timerid;
struct sigevent sev;
struct itimerspec its;
long long freq_nanosecs;
sigset_t mask;
struct sigaction sa;
sem_t sem[NUM_THREADS];
sem_t mute;
pthread_t tid[NUM_THREADS];
int state = 0;
static void handler(int sig, siginfo_t *si, void *uc)
{
ret = sem_post(&sem[(state+1)%NUM_THREADS]);
if (ret)
{
printf("Error in Sem Post\n");
}
state++;
}
void *threadA(void *data_)
{
int i = 0, s,n,value;
long int loopNum;
int turn = (intptr_t)data_;
struct timespec tval_result,tval_result2;
int sid = syscall(SYS_gettid);
FILE *fp;
fp=fopen("ipc.out","a");
fprintf(fp,"thread_%d %d\n",turn,sid);
fclose(fp);
int counter=0;
while(1)
{
ret = sem_wait(&sem[turn]);
if (ret)
{
printf("Error in Sem Post\n");
}
//printf("Thread # -> %d\n",turn);
its.it_value.tv_sec = 0;
its.it_value.tv_nsec = 14000;
its.it_interval.tv_sec = 0;
its.it_interval.tv_nsec = 0;
ret = timer_settime(timerid, 0, &its, NULL);
if (ret < 0)
perror("timer_settime");
// Some heavy work
counter++;
if(counter==100)
break;
}
printf("finished %d\n",turn);
}
int main(int argc, char *argv[])
{
int data = 0;
int err,i;
sa.sa_flags = SA_RESTART;
sa.sa_sigaction = handler;
sigemptyset(&sa.sa_mask);
sigaction(SIG, &sa, NULL);
sev.sigev_notify = SIGEV_SIGNAL;
sev.sigev_signo = SIG;
sev.sigev_value.sival_ptr = &timerid;
ret = timer_create(CLOCKID, &sev, &timerid);
if (ret < 0)
perror("timer_create");
sem_init(&sem[0], 0, 1);
for (i = 1; i < NUM_THREADS; ++i)
{
sem_init(&sem[i], 0, 0);
}
while(data < NUM_THREADS)
{
//create our threads
err = pthread_create(&tid[data], NULL, threadA, (void *)(intptr_t)data);
if(err != 0)
printf("\ncan't create thread :[%s]", strerror(err));
data++;
}
pthread_exit(NULL);
}
根據這個,這個程序應該打印
finished 0
finished 1
finished 2
finished 3
finished 4
finished 5
finished 6
finished 7
finished 8
finished 9
其中一些打印這樣的,但大部分時間,程序掛斷的時間。
謝謝!這是有道理的,你解釋。我會修改程序以避免任何競爭條件。雖然,你上面告訴我的變化並不是解決這個問題,但它是值得的。 – Scissor
感謝@kaylum的解釋。它解決了我的問題。 – Scissor