Re: pthread_t ids of threads not showed by "thread info"

[Stefano Sabatini <stefano.sabatini-lala@poste.it>]

On date Thursday 2010-04-22 17:18:55 +0200, Stefano Sabatini wrote:
> Hi all,
> 
> $ gdb --version
> GNU gdb (GDB) 7.1
> 
> (gdb) info threads
> * 9 Thread 25919  0x0040cc7d in PSafeObject::LockReadOnly (this=0xb6d3d1d8)
>     at ../common/safecoll.cxx:144
>   8 Thread 25920  0x00885402 in __kernel_vsyscall ()
>   7 Thread 25921  0x00885402 in __kernel_vsyscall ()
>   6 Thread 25922  0x00885402 in __kernel_vsyscall ()
>   5 Thread 25927  0x00885402 in __kernel_vsyscall ()
>   4 Thread 25928  0x00885402 in __kernel_vsyscall ()
>   3 Thread 16215  0x00885402 in __kernel_vsyscall ()
>   2 Thread 16216  0x00885402 in __kernel_vsyscall ()
>   1 Thread 25917  0x00885402 in __kernel_vsyscall ()
> (gdb) help info thread
> IDs of currently known threads.
> 
> This shows the gdb thread number, the process ID and I don't know
> what's contained in the fourth column, but that's for sure cannot be
> the same as the pthread_t id as it is the same for all the threads.
> 
> On another machine I get this output:
>   3 Thread 0xb7642b70 (LWP 3334)  (running)
>   2 Thread 0xb7e43b70 (LWP 3333)  (running)
> * 1 Thread 0xb7e446c0 (LWP 3327)  0xb7fe1424 in __kernel_vsyscall ()
> 
> Can you explain the differences, and why are there in the first place?
> 
> Also in the first scenario I cannot get the pthread_t information, which
> is shown in the third column of the second scenario.

The difference between the first and the second scenario is that the
first output was issued debugging a core, the second one by running a
process through gdb run.

May be possible that it is not possible to extract the pthread_t
info from a core file? Can you explain why?

[...]

Regards.