ptrace & threads

Kevin Wooten kevin at
Fri Jul 18 07:57:30 PDT 2003

John wrote:

>----- Julian Elischer's Original Message -----
>>It is teh nextthing to look at..
>>The ptrace interface doesn't extend to coverthreads at all.
>>We willneed to design somewhole new system..
>>One posibility is the benedict arnold thread(*), that
>>talks with the debugger and controlls teh other threads..
>Well, hoping not to create a NIH discussion, but OS/2 had/has
>a nice interface for thread debugging. Used it years ago as
>a model for setting up an environment on the mainframe (vm).
>One thing to remember, a failed thread on one cpu has no effect
>on any threads running on other physicals.  You literally
>need a way to control how many threads can run in parallel, how
>many physical cpus they can use, and in some circumstances,
I believe that on Linux there is a different process id for different 
kernel threads, is that the same, or is there a parallel for FreeBSD 5 
(4.x uses user threads correct?). If that is true, could ptrace allow 
you to use a process id for a specific thread instead of the entire 
process. Then a signal (for traced processes) whenever a thread is 
started or stopped, and you should be able to control the state of 
threads. This is probably somewhat simplistic since I do not understand 
the whole KSE thing (but it sounds great). I am very interested in 
making GDB support threading very intuitively, as it is a big pain write 
now. For FreeBSD 4.x, could the idea Julian had (benedict arnold 
thread), be used to control the user threads library.


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