bin/58687: gethostbyname leaks kqueue file descriptors with pthreads and static linking

Jonathan Lennox lennox at
Wed Oct 29 08:40:24 PST 2003

>Number:         58687
>Category:       bin
>Synopsis:       gethostbyname leaks kqueue file descriptors with pthreads and static linking
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Oct 29 08:40:20 PST 2003
>Originator:     Jonathan Lennox
>Release:        FreeBSD 5.1-RELEASE-p10 i386
Columbia University
System: FreeBSD 5.1-RELEASE-p10 FreeBSD 5.1-RELEASE-p10 #8: Sun Oct 5 23:47:09 EDT 2003 lennox at i386

The system has been patched by adding
src/lib/libc_r/uthread/uthread_kqueue.c, aligning it with -CURRENT.  (This
is mp's patch of 2003-07-25.)


When linking with a static libc_r and libc, gethostbyname() leaks kqueue
file descriptors.  (I actually first observed this with libc_r_p.a and
libc_p.a, i.e. compiling and linking with -pg, but the same thing happens
when linking with -static.)

This is because &_kqueue isn't included in the 'references' array in
uthread_init.c.  There's no outstanding unresolved link to _kqueue when
libc_r is linked in, so the linker only picks up the version from libc.

See also closed PRs kern/55007 and bin/55879, which are this same problem
with dynamic libraries, now fixed in -CURRENT and -STABLE.


Compile the following program with static libc and libc_r, either with
-static or -pg:

#include <stdio.h>
#include <pthread.h>
#include <netdb.h>

void* the_thread(void* dummy)
  int i;
  for (i = 0; i < 50; i++) {

  return NULL;

int main(void)
  pthread_t dummy;
  pthread_create(&dummy, NULL, &the_thread, NULL);


  return 0;

Before the program exits, use lsof to observe its open file descriptors.
Notice that it has 50 KQUEUE descriptors open.

In -CURRENT, this problem does not occur if you use dynamic libc and libc_r,
though it does in 5.1-RELEASE.  


Apply the following patch and rebuild:

--- lib/libc_r/uthread/uthread_init.c.orig	Wed Oct 29 11:00:53 2003
+++ lib/libc_r/uthread/uthread_init.c	Wed Oct 29 11:01:21 2003
@@ -99,6 +99,7 @@
+	&_kqueue,

As a workaround:

Add the command-line option -u kqueue (-Wl,-u,kqueue from gcc) when

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