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#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/file.h>
#include <sys/types.h>
#include <unistd.h>
#include <wait.h>
#define println(fmt, args...) printf(fmt"\n", ##args)
#define log(fmt, args...) println("[p%u][t%lu]"fmt, getpid(), pthread_self(), ##args)
const char *lockpath = "./f.lock";
int flock_wrap(int fd, int op) {
int ret = flock(fd, op);
if (ret == -1) {
perror("flock error");
}
return ret;
}
int flock_sh(int fd) {
log("flock sh, fd: %d", fd);
return flock_wrap(fd, LOCK_SH | LOCK_NB);
}
int flock_ex(int fd) {
log("flock ex, fd: %d", fd);
return flock_wrap(fd, LOCK_SH | LOCK_NB);
}
int unlock(int fd) {
log("flock unlock, fd: %d", fd);
return flock_wrap(fd, LOCK_UN);
}
typedef void *(*StartRoutine)(void *);
pthread_t spawn(StartRoutine start, void *arg) {
pthread_t tid;
int ret = pthread_create(&tid, NULL, start, arg);
if (ret == -1) {
perror("pthread create error");
return 0;
}
return tid;
}
void do_something() {
log("do some things...");
sleep(2);
}
void do_something_wrap() {
int fd = open(lockpath, O_WRONLY | O_CREAT);
log("open %s as %d", lockpath, fd);
if (fd == -1) {
perror("open error");
return;
}
if (flock_sh(fd) != -1) {
do_something();
}
log("close %d", fd);
close(fd);
}
void *thread_start(void *notused) {
do_something_wrap();
return NULL;
}
void fork_exec() {
pid_t pid = fork();
if (pid == 0) {
log("In child");
execl("/bin/bash", "/bin/bash", "./do.sh", NULL);
exit(0);
} else {
waitpid(pid, NULL, WUNTRACED);
}
}
int main(int argc, char **argv) {
log("main");
pthread_t tid = spawn(thread_start, NULL);
sleep(1);
fork_exec();
pthread_join(tid, NULL);
return 0;
}
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