close() of active socket does not work on FreeBSD 6

[Achilleas Mantzios]

Στις Δευτέρα 11 Δεκέμβριος 2006 17:07, ο/η Arne H. Juul έγραψε:
> On Mon, 11 Dec 2006, Arne H. Juul wrote:
> > I've had problems with some tests hanging on FreeBSD 6/amd64. This
> > happens both with diablo-1.5.0_07-b01 and the java/jdk15 compiled from
> > ports.
> >
> > After much digging we've determined that the root cause is that
> > the guarantee in the socket.close() API, see the documentation at
> > http://java.sun.com/j2se/1.5.0/docs/api/java/net/Socket.html#close()
> > isn't fulfulled - the thread blocked in I/O on the socket doesn't wake
> > up.
>
> Looking at the Java VM source code it does some tricks with dup2() to
> reopen the close()'d filedescriptor, making it point to a filedescriptor
> that's pre-connected to a closed socket.
>
> A small C program that duplicates this (using pipes to make it a bit
> simpler) follows.  I'm not sure if any standards demand that this
> works like it used to on FreeBSD 4 / libc_r, but since Java uses it it
> would be really nice if this could be made to work in FreeBSD 6 (libthr
> and libpthread).   Or maybe somebody has another suggestions on how to
> implement the Java close() semantics?
>

I forgot to mention that all my tests were on 386. (So most probably it's not 
amd64 related).
And indeed in FreeBSD 6, by mapping libpthread.so.2 to libc_r.so.6
FooConn seems to work correctly.
Only with libthr.so.2 / libpthread.so.2 the problem exists.

> Anyway, the following C program works as intended on FreeBSD 4,
> hangs on FreeBSD 6 (amd64), compiled with:
>  	 cc -Wall -pthread read_dup2.c -o read_dup2
>
>
> #include <fcntl.h>
> #include <stdlib.h>
> #include <stdio.h>
> #include <unistd.h>
> #include <pthread.h>
>
> int p[2];
>
> void *run(void *arg) {
>    ssize_t res;
>    char tmp[128];
>    fprintf(stderr, "reading...\n");
>    res = read(p[0], tmp, sizeof(tmp));
>    fprintf(stderr, "read result: %d\n", (int)res);
>    if (res < 0) {
>      perror("read");
>    }
>    return arg;
> }
>
> int main(int argc, char **argv) {
>    pthread_t t;
>    int d = open("/dev/null", O_RDONLY);
>    if (pipe(p) != 0) {
>      perror("pipe");
>      return 1;
>    }
>    if (pthread_create(&t, NULL, run, NULL) != 0) {
>      perror("thread create");
>      return 1;
>    }
>    sleep(1);
>    d = open("/dev/null", O_RDONLY);
>    if (d < 0) {
>      perror("open dev null");
>      exit(1);
>    }
>    if (dup2(d, p[0]) < 0) {
>      perror("dup2");
>      exit(1);
>    }
>    if (pthread_join(t, NULL) != 0) {
>      perror("thread join");
>      exit(1);
>    }
>    return 0;
> }
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-- 
Achilleas Mantzios