[uml-devel] Re: Why uml-add-tls-support-debug-check-never-works is needed

[uml-devel] Re: Why uml-add-tls-support-debug-check-never-works is needed

[Jeff Dike]

On Sat, Mar 25, 2006 at 12:28:09AM +0100, Blaisorblade wrote:
> BUT, this context switch at the thread born is special: the thread being 
> switched away switches to a new thread not in the body of the new thread's 
> call to switch_to_skas->switch_threads(), but in the body of thread_wait()! 
> At that point, we lose the call to arch_switch_to_skas()!

Yuck yuck yuck.  Nice spotting.

There's an obvious one-line fix for this, but I wonder if we ought to
try some restructuring to avoid this sort of thing in the future.

> Questions and notes:
> 
> *) Why does arch/um/os-Linux/skas/process.c has still one siglongjmp() call 
> and sigjmp_buf vars, and that has no comments?

I'm tempted to say that I just missed the call somehow.  I see no
reason for that to be different, especially since it's preceded by a
UML_SIGSETJMP.  As for the sigjmp_buf variables, I don't get your
point.  Those haven't changed.

> *) Also, why thread_wait and thread_switch are almost identical, yet they're 
> two different functions?

switch_threads?  In order to merge them, you'd have to pass in the 1
and the INIT_JMP_REMOVE_SIGSTACK, which I have conceptual problems
with.  First, that makes the callers know things that they probably
shouldn't.  Second, the 1 and the INIT_JMP_REMOVE_SIGSTACK have
completely different meanings.  One is a message to the initial thread
that it has to do something.  The 1 is a message to setjmp that is has
been longjmp-ed to.

> *) Btw, the naming sucks - if I find better names for new_thread, 
> new_thread_proc and such, would they be accepted?

Sure, good names are always appreciated.

				Jeff


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