Re: Design hole in nptl (and more general in POSIX threads)

Um.. I think this proposal is reasonable. Stack scanning is essential
for the performance of managed runtime systems, NPTL certainly can do
better in this field before special hardware support is available.

 

-xiaofeng

 

Date: Wed, 17 Dec 2003 12:29:49 +0000

From: Jamie Lokier <[email protected]>

To: Dragi?a Duri? <[email protected]>

Cc: [email protected]

Subject: Re: Design hole in nptl (and more general in POSIX threads)

 

Dragi?a Duri? wrote:

> Advanced (probably every) garbage collector needs to scan threads 

> stacks for pointers to traced heap being kept in local variable spaces


> of procedures in suspended threads. While suspending of other threads 

> is possible in portable way (thanks to this list for help) it is not 

> possible, in portable way, to get exact position of active portion of 

> threads stack. Only way (I know of) goes through pthread_getattr_np() 

> call which gives only partial information - one needs stack pointer 

> (obtainable only through oh-so-portable pthread debug interface and 

> only after hacking deeply nested include files for exact info on 

> position of stack pointer in greglist structure.

 

You can send a signal such as SIGUSR1 to all threads and have them
record the stack pointer in a data structure before putting themselves
to sleep.

 

> Meaning, it is not possible to implement this fundamental feature of 

> advanced high-level langugages in portable way.

>

> Are there plans to fix this somewhere before greglist? :)

 

Well, no matter what changes are made to nptl, it's not going to make
the solution portable to non-nptl platforms is it?

 

-- Jamie