Date: Wed, 29 Oct 2003 11:31:45 -0500 (EST) From: Jonathan Lennox <lennox@cs.columbia.edu> To: FreeBSD-gnats-submit@FreeBSD.org Subject: bin/58687: gethostbyname leaks kqueue file descriptors with pthreads and static linking Message-ID: <200310291631.h9TGVjLu005481@cnr.cs.columbia.edu> Resent-Message-ID: <200310291640.h9TGeK3K039827@freefall.freebsd.org>
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>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
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Wed Oct 29 08:40:20 PST 2003
>Closed-Date:
>Last-Modified:
>Originator: Jonathan Lennox
>Release: FreeBSD 5.1-RELEASE-p10 i386
>Organization:
Columbia University
>Environment:
System: FreeBSD cnr.cs.columbia.edu 5.1-RELEASE-p10 FreeBSD 5.1-RELEASE-p10 #8: Sun Oct 5 23:47:09 EDT 2003 lennox@cnr.cs.columbia.edu:/usr/obj/usr/src/sys/CNR 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.)
>Description:
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.
>How-To-Repeat:
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++) {
gethostbyname("www.freebsd.org");
}
return NULL;
}
int main(void)
{
pthread_t dummy;
pthread_create(&dummy, NULL, &the_thread, NULL);
getchar();
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.
>Fix:
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 @@
&_getsockopt,
&_ioctl,
&_kevent,
+ &_kqueue,
&_listen,
&_nanosleep,
&_open,
As a workaround:
Add the command-line option -u kqueue (-Wl,-u,kqueue from gcc) when
linking.
>Release-Note:
>Audit-Trail:
>Unformatted:
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