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Re: BUG: GDB >=6 vfork from pthread fails with 2.6 vanilla kernels
- From: "Jonathan A. George" <JAGeorge at greshamstorage dot com>
- To: Daniel Jacobowitz <drow at false dot org>
- Cc: gdb at sources dot redhat dot com
- Date: Mon, 17 May 2004 12:39:49 -0500
- Subject: Re: BUG: GDB >=6 vfork from pthread fails with 2.6 vanilla kernels
- References: <40A4E1EA.8080603@greshamstorage.com> <20040517011237.GA27529@nevyn.them.org>
- Reply-to: JAGeorge at greshamstorage dot com
Daniel Jacobowitz wrote:
On Fri, May 14, 2004 at 10:12:42AM -0500, Jonathan A. George wrote:
BUG: GDB >=6 vfork from pthread fails with 2.6 vanilla kernels
Very simple to duplicate:
Run popen() from within a pthread_create() thread while sleeping in
the base process.
(NOTE: works perfectly outside of GDB and under GDB with 2.4 kernel
pthreads)
Environment:
Any 2.6 series kernel (tested 2.6.0 - 2.6.6 vanilla kernel.org)
Any GDB (tested 6.0 - current CVS)
Any GCC linked with -lpthread (tested 3.0.4 - 3.3.3)
GDB output from test program:
Detaching after fork from child process 7020.
warning: Unexpected waitpid result 00117f when waiting for vfork-done
linux-nat.c:450: internal-error: unknown ptrace event 5
A problem internal to GDB has been detected,
further debugging may prove unreliable.
Quit this debugging session? (y or n)
Observations:
It seems as if GDB in linux-nat.c is trying to associate the vfork()d
popen()d process with the root process instead of the parenting
thread started by the root process.
Did you really try current CVS? I checked in a fix for this a couple
of weeks ago.
Technically I tried the current CVS snapshot, but to be sure I just
checked out the entire tree using the following commands:
cvs -z2 -d :pserver:anoncvs@sources.redhat.com:/cvs/src co gdb+dejagnu
cvs -z2 up
./configure
make
su
make install
I even moved aside the distribution gdb:
su
cd /usr/bin
mkdir gdb.distro
mv *gdb* gdb.distro
One possible note of interest; when gdb starts for my test case I see
these messages:
GNU gdb 2004-04-17-cvs
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you
are
welcome to change it and/or distribute copies of it under certain
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB. Type "show warranty" for details.
This GDB was configured as "i686-pc-linux-gnu"...Using host libthread_db
library
"/lib/tls/libthread_db.so.1".
(gdb) run
Starting program: /home/jageorge/example/a.out
[Thread debugging using libthread_db enabled]
[New Thread 1076200096 (LWP 30264)]
hello world
[New Thread 1084591024 (LWP 30267)]
If it still doesn't work, please post a test case.
My test case is attached.
--Jonathan--
#include <iostream>
using namespace std;
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
void *
thread_start( void *thread_arg )
{
cout << "arg=" << (long) thread_arg << endl;
FILE *popen_file = popen( "ping -c3 127.0.0.1", "r" );
cout << "errno=" << errno << endl;
if( popen_file )
{
char linebuf[ 0xff ];
char *fgets_result = NULL;
while( NULL !=
(fgets_result = fgets( linebuf, sizeof( linebuf ), popen_file )) )
{
cout << "fgets_result=" << fgets_result;//<< endl;
}
int pclose_result = pclose( popen_file );
cout << "pclose_result=" << pclose_result << endl;
}
return( NULL );
}
int
main()
{
cout << "hello world" << endl;
pthread_t tid = 0;
pthread_attr_t pattr;
pthread_attr_init( &pattr );
pthread_attr_setdetachstate( &pattr, PTHREAD_CREATE_DETACHED );
pthread_create( &tid, &pattr, thread_start, (void *) 12345L );
//pthread_join( tid, NULL );
cout << "sleeping" << endl;
sleep( 20 );
return( 0 );
};