Re: Is the current gdb 5.1 broken for Linuxthreads?

[Eric Paire <paire at ri dot silicomp dot fr>]

> 
> Eric wrote :- 
> 
> >  There is no support for MT core dumps.
> 
> H.J. replied :-
> 
> > Try the current Red Hat kernel/ac kernel. They support it. The patch
> > is very small. I am enclosing it here.
> 
> However inspection shows that that patch does _not_ implement a
> multi-threaded core dump. What it does is to dump a full core file for
> each thread.
> 
> That seems a somewhat perverse approach, given that 
> 
> 1) the ELF core dump format easily handles a genuine multi-threaded
>    core dump (cf Solaris, IRIX, ...)
> 
This is not feasible in Linux as Linus does not want to implement any
specific pthread feature in the kernel (and the core dump is 100%
kernel code), e.g. why a thread doing a fault should kill the other,
perhaps the application is written in such a way that it can recover
from it.

> 2) debuggers already know how to read such multi-threaded core dumps
>    and present them as a process with multiple threads.
> 
The point is that debugger should understand the way MT core dumps are
done

> 3) dumping a full core dump for each thread is (to first
>    approximation) using nthreads too much I/O and nthreads too much
>    disk space.
> 
If you look carefully at it, it only dumps the first thread, and the dump
is no longer allowed for any thread of this process.

> What is wanted is a genuine multi-threaded core dump, not this
> horror...
> 
I would not say that it is, because it exists, and we have been leaving
without anything for years. I would just say that it is a first step
that is more useful that nothing.

-Eric
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ Eric PAIRE
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