Re: using poll on /proc/mdstat

On Mon, 27 Dec 2010 09:21:00 +0800 "kernel.majianpeng"
wrote:

> Hi all:
> read Neil Brown's mail, I modified the function:
> char buff[4096] = {0};
> int fd = open("/proc/mdstat",O_RDONLY);
> if(fd < 0){
> printf("open /proc/mdstat error:%s\n",strerror(errno));
> return -errno;
> }
>
> struct pollfd fds[1];
> int ret;
>
> fds[0].fd = fd;
> fds[0].events = POLLPRI;
> while(1){
> fds[0].fd = fd;
> fds[0].events = POLLPRI;
> ret = poll(fds,1,-1);
> if(ret < 0){
> printf("poll error:%s\n",strerror(errno));
> break;
> }else
> printf("ret value=%d\n",fds[0].revents);
> read(fd,buff,4096);
> memset(buff ,0,4096);
> }
> close(fd);
>
> I add read command and confirm read end of file /proc/mdstat.
> But this fution also to find only one event.

You missed this bit:


> poll will only block again after you read to the end of the file (and thus
> observe any change), and then seek back to the start.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

NeilBrown


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