Re: bin/30756: gdb not usable for live debugging of threaded programs

[Nick Hudson <nick.hudson%gmx.co.uk@localhost>]

On Thursday 22 April 2010 16:20:04 Paul Koning wrote:
>  Antti pointed out a problem in the patch I originally submitted which
>  causes gdb to go into a loop if the child process exits.  The attached
>  updated patch corrects that problem.

This, unfortunately, still has cosmetic issues. See the attached log and the 
"Couldn't get registers: Operation not permitted." at the end of the session

Nick

(gdb) set debug nbsd-thread 1
(gdb) attach 1049
Attaching to process 1049
NTW2: waiting for ptid -1,0, opt 0
NTW2: waitpid errno is 0, pid 1049, status 117f
NTUP: lwpinfo on 0 returns lwp 1, pl_event 0
NTUP: adding first thread ptid 1049,1
NTUP: lwpinfo on 1 returns lwp 0, pl_event 0
NTUP: signalled thread lwpid is 0
NTW2: waiting for ptid 1049,0, opt 1
NTW2: waitpid errno is 0, pid 0, status 0
NTW: no signalled thread
NTW: returning ptid 1049,1
NFIR: ptid 1049,1, regnum 8: 804865a
Reading symbols from /home/nick/gdb/obj/gdb/testsuite/gdb.base/attach...done.
NFIR: ptid 1049,1, regnum 8: 804865a
Reading symbols from /usr/lib/libm.so.0...done.
Loaded symbols for /usr/lib/libm.so.0
Reading symbols from /usr/lib/libc.so.12...done.
Loaded symbols for /usr/lib/libc.so.12
Reading symbols from /usr/libexec/ld.elf_so...done.
Loaded symbols for /usr/libexec/ld.elf_so
[Switching to Thread 1]
main () at ../../../src/gdb/testsuite/gdb.base/attach.c:17
17            local_i++;
(gdb) print should_exit
$1 = 0
(gdb) detach
Detaching from program: /home/nick/gdb/obj/gdb/testsuite/gdb.base/attach, 
process 1049
(gdb) attach 1049
Attaching to program: /home/nick/gdb/obj/gdb/testsuite/gdb.base/attach, process 
1049
NTW2: waiting for ptid -1,0, opt 0
NTW2: waitpid errno is 0, pid 1049, status 117f
NTUP: lwpinfo on 0 returns lwp 1, pl_event 0
NTUP: lwpinfo on 1 returns lwp 0, pl_event 0
NTUP: signalled thread lwpid is 0
NTW2: waiting for ptid 1049,0, opt 1
NTW2: waitpid errno is 0, pid 0, status 117f
NTW: no signalled thread
NTW: returning ptid 1049,0
NFIR: ptid 1049,0, regnum 8: 804865d
Loaded symbols for /usr/lib/libm.so.0
Loaded symbols for /usr/lib/libc.so.12
Loaded symbols for /usr/libexec/ld.elf_so
main () at ../../../src/gdb/testsuite/gdb.base/attach.c:15
15        while (! should_exit)
(gdb) set should_exit=1
(gdb) tbreak 19
Breakpoint 1 at 0x8048666: file ../../../src/gdb/testsuite/gdb.base/attach.c, 
line 19.
(gdb) c
Continuing.
NTR: resuming ptid 1049,0, all threads, signal 0
NTW2: waiting for ptid -1,0, opt 0
NTW2: waitpid errno is 0, pid 1049, status 57f
NTUP: lwpinfo on 0 returns lwp 1, pl_event 1
NTUP: lwpinfo on 1 returns lwp 0, pl_event 0
NTUP: signalled thread lwpid is 1
NTW2: waiting for ptid 1049,0, opt 1
NTW2: waitpid errno is 0, pid 0, status 57f
NTW: Picking ptid 1049,1 out of 1
NTW: returning ptid 1049,1
NFIR: ptid 1049,1, regnum 8: 8048667
NSIR: ptid 1049,1, regnum 8: 8048666
[Switching to Thread 1]
main () at ../../../src/gdb/testsuite/gdb.base/attach.c:19
19        return 0;
(gdb) c
Continuing.
NTR: resuming ptid 1049,1, all threads, signal 0
NTW2: waiting for ptid -1,0, opt 0
NTW2: waitpid errno is 0, pid 1049, status 0
NTUP: signalled thread lwpid is 0
NTW2: waiting for ptid 1049,0, opt 1
NTW2: waitpid errno is 10, pid -1, status 0
NTW: no signalled thread
NTW: returning ptid 1049,1

Program exited normally.
Couldn't get registers: Operation not permitted.
(gdb)