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multithreading and gdbserver
- From: "Frank van Eijkelenburg" <frank dot van dot eijkelenburg at technolution dot nl>
- To: "Gnu Debugger mailing list" <gdb at sources dot redhat dot com>
- Date: Mon, 20 Jan 2003 16:32:39 +0100
- Subject: multithreading and gdbserver
- Reply-to: <frank dot van dot eijkelenburg at technolution dot nl>
Hi, I was wondering if there is anyone who tried remote debbuging a
multithreaded program. I'm using gdb 5.3. I've two linux machines with
redhat installed. If I run gdb and debug a simple multithreaded program
(which is linked against the libpthread library), everything is okay:
[frank@frankVMLinux gdb]$ ./gdb -nx /home/frank/tmp/example_i686/ex1
GNU gdb 5.3
Copyright 2002 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"...
(gdb) list
17 return NULL;
18 }
19
20 int main(void)
21 {
22 int retcode;
23 pthread_t th_a, th_b;
24 void * retval;
25
26 retcode = pthread_create(&th_a, NULL, process, (void *) "a");
(gdb) b 26
Breakpoint 1 at 0x80485d2: file ex1.c, line 26.
(gdb) run
Starting program: /home/frank/tmp/example_i686/ex1
[New Thread 1024 (LWP 5394)]
[Switching to Thread 1024 (LWP 5394)]
Breakpoint 1, main () at ex1.c:26
26 retcode = pthread_create(&th_a, NULL, process, (void *) "a");
(gdb) n
[New Thread 2049 (LWP 5395)]
[New Thread 1026 (LWP 5396)]
Starting process a
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa27 if
(retcode != 0) fprintf(stderr, "create a failed %d\n", retcode);
(gdb) info threads
3 Thread 1026 (LWP 5396) 0x4011e584 in __libc_write () at __libc_write:-1
2 Thread 2049 (LWP 5395) 0x401239f7 in __poll (fds=0x804b72c, nfds=1,
timeout=2000) at ../sysdeps/unix/sysv/linux/poll.c:63
* 1 Thread 1024 (LWP 5394) main () at ex1.c:27
(gdb)
But when I try to debug the same application remote, I can't see any
information about the threads anymore. So, did anyone tried this before?
Output with remote debugging:
On REMOTE machine:
[frank@vmware frank]$ ./gdbserver host:5555 ex1
Process ex1 created; pid = 1034
Remote debugging from host 172.16.10.119
On HOST machine:
[frank@frankVMLinux gdb]$ ./gdb -nx /home/frank/tmp/example_i686/ex1
GNU gdb 5.3
Copyright 2002 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"...
(gdb) target remote 172.16.10.147:5555
Remote debugging using 172.16.10.147:5555
0x40001e20 in ?? ()
(gdb) list
17 return NULL;
18 }
19
20 int main(void)
21 {
22 int retcode;
23 pthread_t th_a, th_b;
24 void * retval;
25
26 retcode = pthread_create(&th_a, NULL, process, (void *) "a");
(gdb) b 26
Breakpoint 1 at 0x80485d2: file ex1.c, line 26.
(gdb) handle SIG32 nostop
Signal Stop Print Pass to program Description
SIG32 No Yes Yes Real-time event 32
(gdb) handle SIG32 noprint
Signal Stop Print Pass to program Description
SIG32 No No Yes Real-time event 32
(gdb) c
Continuing.
Breakpoint 1, main () at ex1.c:26
26 retcode = pthread_create(&th_a, NULL, process, (void *) "a");
(gdb) n
27 if (retcode != 0) fprintf(stderr, "create a failed %d\n",
retcode);
(gdb) n
28 retcode = pthread_create(&th_b, NULL, process, (void *) "b");
(gdb) info threads
1 Thread 1034 main () at ex1.c:28
(gdb) n
29 if (retcode != 0) fprintf(stderr, "create b failed %d\n",
retcode);
(gdb) n
30 retcode = pthread_join(th_a, &retval);
(gdb) n
31 if (retcode != 0) fprintf(stderr, "join a failed %d\n", retcode);
(gdb) n
32 retcode = pthread_join(th_b, &retval);
(gdb) n
33 if (retcode != 0) fprintf(stderr, "join b failed %d\n", retcode);
(gdb) n
34 return 0;
(gdb) info threads
1 Thread 1034 main () at ex1.c:34
(gdb) c
Continuing.
Program exited normally.
(gdb)
As you can see, there is no information about other threads (except the main
thread). It also didn't tell the user that a thread is created. Why is this
in the first case working and with remote debugging not anymore. If somebody
can explain this, I would really appreciate that...
TIA,
Frank