> So, I've been poking around at our debugging support lately, and I
> had remembered Nathan complaining about ptrace(2), specifically that
> it pretty much sucks when it comes to multiple LWPs.
> 
> It seems to me that we could simply add a ptrace(2) request to "set
> which LWP this request is for".

Is it interesting to compare what other operating systems have done?
HP-UX introduced ttrace(2) to overcome the limitations of ptrace(2)
with multithreaded processes, and HP contributed changes to gdb to
enable it to use ttrace(2).

http://docs.hp.com//hpux/onlinedocs/B2355-90682/00/02/219-con.html

I don't know how Solaris supports debugging multithreaded processes
as its ptrace(2) manual page doesn't refer to threads at all.

http://docs.sun.com:80/ab2/coll.40.6/REFMAN2/@Ab2PageView/54414?Ab2Lang=C&Ab2Enc=iso-8859-1

Regards,

Giles