关于记录锁的struct flock结构中返回的pid问题
1.c
/**************************************************************************************//* 关于记录锁的struct flock结构中返回的pid问题 返回的不是持有锁的那个进程ID吗？ *//*************************************************************************************/#include <stdio.h>#include <unistd.h>#include <fcntl.h>#include <errno.h>#include "SynchroProcess.h"int lock_reg(int fd, int cmd, int l_type, off_t l_start, short where, off_t l_len){ struct flock lock; lock.l_type = l_type; lock.l_whence = where; lock.l_start = l_start; lock.l_len = l_len; return fcntl(fd, cmd, &lock);}#define read_lock(fd, offset, where, len) \ lock_reg(fd, F_SETLK, F_RDLCK, offset, where, len)#define readw_lock(fd, offset, where, len) \ lock_reg(fd, F_SETLKW, F_RDLCK, offset, where, len) #define write_lock(fd, offset, where, len) \ lock_reg(fd, F_SETLK, F_WRLCK, offset, where, len)#define writew_lock(fd, offset, where, len) \ lock_reg(fd, F_SETLKW, F_WRLCK, offset, where, len)#define un_lock(fd, offset, where, len) \ lock_reg(fd, F_SETLK, F_UNLCK, offset, where, len)pid_t lock_test(int fd, int type, off_t start, short where, off_t len){ struct flock lock; lock.l_type = type; lock.l_start = start; lock.l_whence = where; lock.l_len = len; if (fcntl(fd, F_GETFL, &lock) < 0) { printf("fcntl error!\n"); } if (lock.l_type == F_UNLCK) { return 0; } return lock.l_pid; }static void lockabyte(const char *name, int fd, off_t offset){ if (writew_lock(fd, offset, SEEK_SET, 1) < 0) { printf("writew_lock error!\n"); } printf("%s: got the lock, byte %ld\n", name, offset);} int main(){ int fd; pid_t pid; if ((fd = creat("temp", O_RDWR )) < 0) { printf("creat error!\n"); } if (write(fd, "ab", 2) != 2) { printf("write error!\n"); } TELL_WAIT(); if ((pid = fork()) < 0) { printf("fork error!\n"); } else if (pid == 0) { printf("int child!\n"); lockabyte("temp", fd, 0); TELL_PARENT(getppid()); WAIT_PARENT(); //返回的不是持有锁的那个进程ID吗？怎么不是父ID啊？ printf("l_pid = %d ppid = %d pid = %d\n", lock_test(fd, F_GETFL, 1, SEEK_SET, 1), getppid(), getpid()); //lockabyte("temp", fd, 1); //这里产生死锁。。。。 TELL_PARENT(getppid()); } else { WAIT_CHILD(); printf("in parent!\n"); lockabyte("temp", fd, 1); TELL_CHILD(pid); WAIT_CHILD(); } return 0;}运行结果：[root@localhost work1]# gcc *.c -o 1[root@localhost work1]# ./1int child!temp: got the lock, byte 0in parent!temp: got the lock, byte 1l_pid = 1104221896 ppid = 4788 pid = 4789 //lock__pid返回的是什么啊？[root@localhost work1]# //#include "SynchroProcess.h"#include <stdio.h>#include <stdlib.h>#include <unistd.h>#ifndef SYNCHRO_PROCESS#define SYNCHRO_PROCESSvoid TELL_WAIT(void); //提示有个等待void TELL_PARENT(pid_t pid); //告诉父亲等待void TELL_CHILD(pid_t pid); //告诉孩子等待void WAIT_PARENT( void ); //发信息解除父亲等待void WAIT_CHILD( void ); //发信息解除孩子等待#endif
/*********************************************************************************//* 进程同步的函数实现及其应用。*//********************************************************************************/#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <signal.h>#include "SynchroProcess.h"#include <sys/types.h>static volatile int sigflag; static sigset_t newmask, oldmask,zeromask;static void sig_usr(int signo){ sigflag = 1;} void TELL_WAIT(void){ if (signal(SIGUSR1, sig_usr) == SIG_ERR) { printf("signal1 error!\n"); } if (signal(SIGUSR2, sig_usr) == SIG_ERR) { printf("signal2 error!\n"); } sigemptyset(&zeromask); sigemptyset(&newmask); sigaddset(&newmask, SIGUSR1); sigaddset(&newmask, SIGUSR2); if (sigprocmask(SIG_BLOCK, &newmask, &oldmask) < 0) { printf("sigprocmask error!"); }}void TELL_PARENT(pid_t pid){ kill(pid, SIGUSR2);}void TELL_CHILD(pid_t pid){ kill(pid, SIGUSR1);}void WAIT_PARENT( void ){ while (sigflag == 0) { sigsuspend(&zeromask); } sigflag = 0; if (sigprocmask(SIG_SETMASK, &oldmask, NULL) < 0) { printf("SIG_SETMASK error!\n"); }}void WAIT_CHILD( void ){ while (sigflag == 0) { sigsuspend(&zeromask); } sigflag = 0; if (sigprocmask(SIG_SETMASK, &oldmask, NULL) < 0) { printf("SIG_SETMASK error!\n"); }}