Re: [RFA] Don't use thread_db on corefiles

[Michael Snyder <msnyder@cygnus.com>]

Daniel Jacobowitz wrote:
> 
> On Thu, Dec 13, 2001 at 03:37:04PM -0800, Andrew Cagney wrote:
> > >On Thu, Dec 13, 2001 at 03:04:07PM -0800, Michael Snyder wrote:
> > >
> > >>OK.  I'd like to see that patch when it's ready.
> > >>Do you use only lwp's, or do you use glibc/libpthread threads?
> > >>If you use library threads, are you saving their info in the
> > >>core file, or are you only saving the info for the lwp's?
> > >
> > >
> > >It's completely thread-package-agnostic.  I dump all LWPs sharing the
> > >same VM, as a fairly reliable marker (I'd use 2.4 threadgroups, but
> > >LinuxThreads doesn't use them...)
> >
> >
> > Ok.  So you're dumping out the raw data that libthread-db would use to
> > recreate the current thread state from the raw LWP state.
> >
> >
> > >So there is enough information there for lin-lwp to parse the threads,
> > >if we stubbed out its attempts to write, I expect.  But since the
> > >current Linux threads model has one thread per process, I can simply
> > >use the corefile.c thread support instead, which I'd rather do.
> >
> >
> > Er, careful.  I think lin-lwp should be fixed.  lin-lwp should be
> > interpreting the raw LWP data translating it into user level threads.
> > (Why it writes to the target just sounds like a bug.)
> 
> Strongly object.
> 
> Why?  Because thread_db is only usable natively!  lin-lwp is not fit
> for cross or remote debugging and never can be. 

Maybe so -- maybe not.  But at the moment we're talking about core
files.
Let's keep to one discussion at a time.

> I am testing with MIPS
> cores on an x86-linux host.  Right now it "works" because thread-db is
> not compiled in; if I had an --enable-targets=i386-linux,mipsel-linux
> it would be, though.

Assuming your MIPS remote target is multi-threaded, that would
definitely
confuse thread-db, yes.  But why would you want to do that?  

It seems like you are maybe trying to be more multi-arch than 
thread-db is designed for.  If the problem is that thread-db 
is not multi-arch enough, then let's address that problem.

> If you want to break lin-lwp up into pieces such that one of them can
> do this, you might as well abandon using thread_db at all.  The kernel
> has enough information to tell you about all the threads; it does so.

Hold on -- I think we're having too many conversations at once.
The kernel doesn't know anything about glibc threads, which are
the only threads that thread-db is concerned with.