Re: select implementation not POSIX compliant?

[Steven Dake]

You will find poll works as you desire but select does not.  I recommend
porting to poll anyway; select sucks bad.  You might even try out epoll
in 2.6.

Thanks
Good luck

On Wed, 2004-08-11 at 12:40, Alex Riesen wrote:
> On linux-kernel, Nick Palmer wrote:
> > I am working on porting some software from Solaris to Linux 2.6.7. I
> > have run into a problem with the interaction of select and/or
> > recvmsg and close in our multi-threaded application. The application
> > expects that a close call on a socket that another thread is
> > blocking in select and/or recvmsg on will cause select and/or
> > recvmsg to return with an error. Linux does not seem to do this. (I
> > also verified that the same issue exists in Linux 2.4.25, just to be
> > sure it wasn't introduced in 2.6 in case you were wondering.)
> 
> It works always for stream sockets and does not at all (even with
> shutdown, even using poll(2) or read(2) instead of select) for dgram
> sockets.
> 
> What domain (inet, local) are your sockets in?
> What type (stream, dgram)?
> 
> There will probably be a problem anyway with changing the behaviour:
> there surely is lots of code, which start complaining about select and
> poll finishing "unexpectedly".
> 
> I used this to check:
> 
> #include <unistd.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <sys/socket.h>
> #include <sys/wait.h>
> #include <netinet/in.h>
> #include <fcntl.h>
> 
> int main(int argc, char* argv[])
> {
>     int status;
>     int fds[2];
>     fd_set set;
> #if 0
>     puts("stream");
>     if (  socketpair(PF_LOCAL, SOCK_STREAM, 0, fds) < 0 )
> #else
>     puts("dgram");
>     if (  socketpair(PF_LOCAL, SOCK_DGRAM, 0, fds) < 0 )
> #endif
>     {
> 	perror("socketpair");
> 	exit(1);
>     }
>     fcntl(fds[0], F_SETFL, fcntl(fds[0], F_GETFL) | O_NONBLOCK);
>     fcntl(fds[1], F_SETFL, fcntl(fds[1], F_GETFL) | O_NONBLOCK);
>     switch ( fork() )
>     {
>     case 0:
> 	sleep(1);
> 	close(fds[0]);
> 	shutdown(fds[1], SHUT_RD);
> 	close(fds[1]);
> 	exit(0);
> 	break;
>     case -1:
> 	perror("fork");
> 	exit(1);
>     }
>     close(fds[1]);
>     FD_ZERO(&set);
>     FD_SET(fds[0], &set);
>     select(fds[0] + 1, &set, NULL, NULL, 0);
>     wait(&status);
>     return 0;
> }
> 
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