Re: gdb show thread names

[Jonny Grant <jg@jguk.org>]

On 15/06/2020 17:21, Philippe Waroquiers wrote:
> On Mon, 2020-06-15 at 16:51 +0100, Pedro Alves wrote:
>>
>> Starting program: /home/pedro/brno/pedro/gdb/binutils-gdb/build/gdb/testsuite/outputs/gdb.threads/names/names 
>> [Thread debugging using libthread_db enabled]
>> Using host libthread_db library "/lib64/libthread_db.so.1".
>> [New Thread 0x7ffff74b8700 (LWP 24171) "main"]
>> [New Thread 0x7ffff6cb7700 (LWP 24172) "main"]
>> [New Thread 0x7ffff64b6700 (LWP 24173) "main"]
>>
>> Thread 1 "main" hit Breakpoint 1, all_threads_ready () at /home/pedro/gdb/binutils-gdb/src/gdb/testsuite/gdb.threads/names.c:51
>> 51      }
>> (gdb) info threads 
>>   Id   Target Id                                  Frame 
>> * 1    Thread 0x7ffff7fb5740 (LWP 24170) "main"   all_threads_ready () at /home/pedro/gdb/binutils-gdb/src/gdb/testsuite/gdb.threads/names.c:51
>>   2    Thread 0x7ffff74b8700 (LWP 24171) "carrot" 0x00007ffff7bc89aa in futex_wait (private=0, expected=4, futex_word=0x7fffffffd604) at ../sysdeps/unix/sysv/linux/futex-internal.h:61
>>   3    Thread 0x7ffff6cb7700 (LWP 24172) "potato" 0x00007ffff7bc89aa in futex_wait (private=0, expected=4, futex_word=0x7fffffffd604) at ../sysdeps/unix/sysv/linux/futex-internal.h:61
>>   4    Thread 0x7ffff64b6700 (LWP 24173) "celery" 0x00007ffff7bc89aa in futex_wait (private=0, expected=4, futex_word=0x7fffffffd604) at ../sysdeps/unix/sysv/linux/futex-internal.h:61
>> (gdb) 
>>
>> I.e., printing the thread name when the thread is created
>> looks more confusing than helpful to me.
> Yes, that is confusing.
> 
> And for the following events, when I tried, the patch was far to be ready 
> e.g. for the exit events, it gives (for the above):
>   (gdb) c
>   Continuing.
>   [Thread 0x7ffff743d700 (LWP 22783) exited]
>   [Thread 0x7ffff7c3e700 (LWP 22782) exited]
>   [Thread 0x7ffff7c3f740 (LWP 22778) "main" exited]
> 
> So, unclear why there is no carrot, potato or celery in the 2 exited threads
> but "main" is present.
> (and sometimes there is no names in any exited event).
> 
> So, when I looked at it, it needed quite some more work ...
> 
> Philippe
> 

Hi, Maybe it is more complicated than it is worth after all.
Although, I did think new threads inherited the process executable name, rather than the main() symbol.

It's easy enough for me to press ^C and then type "info threads" so maybe it is fine as it is.
Would start to get awkward if GDB needs to interrupt and poll the proc "comm" file for each LWP etc

Regards, Jonny