sigset_t wait_set;
sigset_t zero_set;
int sig_no;
struct sigaction act;
const struct timespec tv = {5,0}; //timeout
siginfo_t sig_info ;//传递的信息结构
void sig_pipe(int signo)
{
printf("in sig_pipe () , signo=%d\n",signo);
printf("errno=%d\n",errno);
printf("access_mode = %d\n",access_mode);
//if(errno == EPIPE && access_mode == ACCESS_WRITE ) { //仅对write archive的时候有效
if(access_mode == ACCESS_WRITE )
{ //当no space left的时候，为什么errno=0 ???
printf("in catch function , ENOSPC \n");
RetCode = -TAR_NO_SPACE_LEFT;
}
}
void sighandler_sigchld(int signo)
{
int child_count;
pid_t pid;
int status;
printf("recieved signo = %d\n",signo);
if(signo == SIGCHLD) {
/* Reap defunct children until there aren't any more. */
for(;;)
{
pid = waitpid((pid_t) - 1, &status, WNOHANG); //WNOHANG 防止阻塞
jprintf("\n\n++++++ waitpid retunr pid (%d) , status (%d) \n",pid,status);
if ((int) pid == 0) /* none left */
break;
if ((int) pid < 0)
{
if (errno == EINTR) /* because of ptrace */
continue;
/* ECHILD shouldn't happen with the WNOHANG option, but with
** some kernels it does anyway. Ignore it.
*/
//其他的情况，就说明没有子进程需要回收了， 可以跳出循环
break;
}
}
}
}
void wait_Zombie(void)
{
int child_count;
pid_t pid;
int status;
/* Reap defunct children until there aren't any more. */
for(;;)
{
pid = waitpid((pid_t) - 1, &status, WNOHANG); //WNOHANG 防止阻塞
jprintf("========= in uncompress parent process free Zombie \n"
"waitpid retunr pid (%d) , status (%d) \n",pid,status);
if ((int) pid == 0) /* none left */
break;
if ((int) pid < 0)
{
if (errno == EINTR) /* because of ptrace */
continue;
/* ECHILD shouldn't happen with the WNOHANG option, but with
** some kernels it does anyway. Ignore it.
*/
//其他的情况，就说明没有子进程需要回收了， 可以跳出循环
break;
}
}
}
/*===================================================
创建.tar.gz 文件
这个compress 比 uncompress可简单多了。
this function will return pipe[write] id , then write block into this archive
=================================================== */
int sys_child_open_for_compress_xx (const char *archive_file_path)
{
int parent_pipe[2];
int child_pipe[2];
pid_t grandchild_pid;
pid_t child_pid;
int wait_status;
//siginfo_t sig_info ;//传递的信息结构
sigemptyset(&zero_set);
sigemptyset(&wait_set);
sigaddset(&wait_set,SIGUSR1);
sigprocmask(SIG_SETMASK,&zero_set,NULL);
act.sa_handler = sighandler_usr1;
//act.sa_handler = SIG_DFL;
sigemptyset(&act.sa_mask);
act.sa_flags = SA_SIGINFO; //这个很关键，否则无法用sigqueue() 发送信号
sigaction(SIGUSR1,&act,NULL);
xpipe (parent_pipe);
child_pid = xfork ();
// -------------------------------- parent progress ---------------------------------
if (child_pid > 0)
{
/* The parent tar is still here! Just clean up. */
printf("\n\n--------- in compress : child_pid= %d\n",child_pid);
archive = parent_pipe[PWRITE];
xclose (parent_pipe[PREAD]);
//在这里等待子进程的返回值，来确定是否有必要继续运行下去
again:
sigprocmask(SIG_BLOCK,&wait_set,NULL);
sig_no = sigtimedwait(&wait_set,&sig_info,&tv); //父进程会一直阻塞tv时间，然后就返回
printf("sig_no=%d\n",sig_no);
if(sig_no == -1) { //可能超时，也可能是被别的信号中断，在下面判
printf("sigtimedwait return exception , sig_no = -1\n");
if(errno == EINTR)//interrupted by others signals
{
jprintf("parent process has been interrupted by others signal \n");
jprintf("it will continue to be blocked \n");
goto again;
}
else if(errno == EAGAIN)//resource unavilable , timeout
; //jump out; do nothing
return -TAR_CANNOT_CREATE_ARCHIVE_FILE;
}
else {
printf("child process return value = %d\n",sig_info.si_int);
if(sig_info.si_int > 0) { //信号传递的信息:传递的子进程create的archive的fd
printf("ok\n");
printf("child process create fd=%d\n",sig_info.si_int);
return archive;
}
else
{ // fd <=0
printf("can't create archive file ,please check directory\n");
return -TAR_CANNOT_CREATE_ARCHIVE_FILE;
//FIXME: 我的意思是子进程无法创建archive ， 的时候， 返回负数， 但是archive本身永远是对的
//不过不是大问题，最多没有close(archive)而已。
}
}
//-------------------------------------------------------------------
//return archive; 原来是直接返回，这是不对的，必须经过上面的判断才可
}
else if (child_pid == 0) {
/* The new born child tar is here! */
union sigval rc_val;
//program_name = _("tar (child)");
xdup2 (parent_pipe[PREAD], STDIN_FILENO);//dup2 to stdin
xclose (parent_pipe[PWRITE]);
// if (!_remdev (archive_name_array[0])
// && is_regular_file (archive_name_array[0]))
{
int _tar_gz_fd = 0;
pid_t p_pid = 0;
/* We don't need a grandchild tar. Open the archive and launch the
compressor. */
if (strcmp (archive_file_path, "-")) //最一般的情况,比如 tar zcvf bob.tar.gz system.c update.c
{
_tar_gz_fd = creat (archive_file_path, MODE_RW);
jprintf("in child progress (gzip) ,fd = %d\n",_tar_gz_fd);
rc_val.sival_int = _tar_gz_fd; //传递整型值
//这里要通知父进程
p_pid = getppid();
if(p_pid !=1) { //如果父进程是1（init) , 就不要发信号（事实上没有这种可能，因为父进程已经阻塞了）
jprintf("has send SIGUSR1 signal \n");
sleep(1); //in Marvell 的扳子上，子进程run的太快了，以至于父进程还没有执行到sigtimedwait()函数
//因此必须sleep一下， 确保父进程已经blocked
sigqueue(p_pid,SIGUSR1,rc_val); //kill的更强的用法，除了kill的功能外，还可以传递整形值和指针
//exit(0); //
}
if (_tar_gz_fd < 0)
{
int saved_errno = errno;
errno = saved_errno;
// open_fatal (archive_file_path);
exit(0);
}
xdup2 (_tar_gz_fd, STDOUT_FILENO); //父进程会把tar的结果输出到 archive中去， gzip到这里取结果！
}
execlp (use_compress_program_option, use_compress_program_option, NULL);
//如果gzip执行正常，就不会执行到下面的代码
jprintf("gzip run status = %d\n",errno);
//exec_fatal (use_compress_program_option);
}
}
}
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