Re: gcore and nptl threads on linux

[Andrew Cagney <ac131313@redhat.com>]

> On Wed, Mar 05, 2003 at 07:56:01PM -0500, Andrew Cagney wrote:
> 
>> 
> 
>> >>I would think the null_ptid would serve in such a case.
> 
>> >
>> >
>> >I guess the issue is that we should be dumping the set of LWPs to the
>> >generated core file, not the set of threads.  It seems to me like GDB
>> >should be aware of the list of LWPs, and it shouldn't be hidden in each
>> >individual thread package.
> 
>> 
>> You mean add them to the `struct thread_info' list?  Why not (ignoring 
>> technical realities for the moment :-)?
> 
> 
> Well, I wouldn't do it that way.  I haven't really designed this, so
> bear with me if it has some squishy spots.
> 
> I think there should be two lists:
>   all threads
>   all lwps

I believe in `zero, one, many':

- lwps
- processes
- threads (as in pthread)
- threads (as in a java interpreter thread)
- tasks (as in ada)

Each has something like:

- an architecture
- a target
- an owner?

For instance, an ada task might be implemented using a p-thread, which 
might in turn be implemented using an lwp-thread.  Only, the task is 
doing an rpc to java interpreter thread running in a separate process.

Each category can either maintain a local private database, or they can 
all share a common database.  If the info is more central, it becomes 
easier for the user to query/manipulate it.

> Should the data structures be the same?  I don't know.  The mapping
> between them would be defined by the thread stratum; its role would be
> to take thread requests, convert them to LWP requests, and pass them
> on.  The process stratum would be responsible for managing all of the
> LWPs.

Things to do today should include throwing out stratum (along with the 
bath water).

> This has some advantages, I think.  Here's one: we would have a logical
> interface for reporting an event from an LWP that doesn't currently
> have a thread.  This happens in LinuxThreads, as I've mentioned
> recently.  The thread stratum could see that the inferior ptid was just
> an LWP id and pass the request along no questions asked.

?  That sounds a bit up-side-down, shouldn't events be propogating up - 
lwp gets to see them before thread?

> Hmm, definitely some loose edges in that one.  Should both an LWP and a
> thread have a regcache?  Might work.

Don't forget that a regcache is just a local performance optimization - 
a look-a-side buffer.

Andrew