Date: Fri, 17 May 2002 15:36:23 -0500 From: Dave Baukus <dbaukus@chiaro.com> To: freebsd-bugs@freebsd.org Subject: ptheread hang Message-ID: <3CE569C7.5010104@chiaro.com>
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In bsd4.0 it is possible to hang a pthread indefinitely due to what I
think is an incorrect interpretation of EAGAIN from the connect() system
call. A TCP, and probably a UDP, connect() will return EAGAIN if
all the ephemeral ports are allocated.
EAGAIN is bubbled up from in_pcbbind() when the connecting socket
requires an implicit bind() and the specified ephemeral port range is
100% allocated.
When EAGAIN is returned to the pthread _connect() implementation it
puts the thread to sleep and waits for poll()/select() to indicate
that the connect is complete:
from bsd4.0/src/lib/libc_r/uthread/uthread_connect.c:
int
_connect(int fd, const struct sockaddr * name, socklen_t namelen)
{
struct sockaddr tmpname;
int errnolen, ret, tmpnamelen;
if ((ret = _FD_LOCK(fd, FD_RDWR, NULL)) == 0) {
if ((ret = _thread_sys_connect(fd, name, namelen)) < 0)
{
if (!(_thread_fd_table[fd]->flags & O_NONBLOCK)
&&
((errno == EWOULDBLOCK) || (errno == EINPROGRESS) ||
(errno == EALREADY) || (errno == EAGAIN)))
{
_thread_run->data.fd.fd = fd;
/* Set the timeout: */
_thread_kern_set_timeout(NULL);
_thread_kern_sched_state(PS_FDW_WAIT,
__FILE__,_LINE__);
...
...
...
The connect will never complete because it was never started; the
TCP never sent a SYN; it is in the closed state; it will remain like
this forever. EAGAIN is not the same as EINPROGRESS.
--
dave baukus@chiaro.com
Chiaro Networks
Richardson Texas
USA
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