Re: [ECOS] Multi thread Debugging

[Jonathan Larmour <jlarmour@redhat.co.uk>]

Fabrice Gautier wrote:
> Si now I see that there is a saved context when there is an interrupt but
> I don't understand how is the context saved when there is a thread switch.
> 
> The macro HAL_THREAD_SWITCH_CONTEXT let me think that there is something
> saved in the stack_ptr member of the Threads while in interrupt_end it is
> saved in the saved_context member.

The stack_ptr member is there for a different purpose than saved_context.
saved_context is for GDB debugging purposes only and provides the full
context. AFAIK interrupt_end is the only place that stores the context in
saved_context.

This is interesting - it's not clear to me either how saved_context is set
if threads get rescheduled for any reason other than an interrupt.

Is this a bug?

I wouldn't have thought this would have caused a problem on the scale
Fabrice is seeing at any rate.

> Then, I'v eseen in GDB that in order to get the information for each thread
> it does a thread switch. How (where?) is a thread switch request from gdb
> done in the Stub?

There is no thread switch in the stub. Look at
kernel/VERSION/src/debug/dbg_gdb.cxx and specifically dbg_threadlist(). It
traverses the list of threads by following the thread list pointers.

Jifl
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