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List:       kde-devel
Subject:    Re: threading in kde
From:       Andrew Sutton <ansutton () sep ! com>
Date:       2001-09-18 19:51:31
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On Thursday 30 August 2001 02:03, Andrew Sutton wrote:
> hi all,
> <snip rest of thread>

hi again.

i was just writing to let you know that i ported all my threading work back 
to qt rewroting the entire thread core. i sent the patches back to trolltech 
and they expressed interest in the changes.

if anybody is interested, let me know, i'll send you the modified files, 
although you'll have to integrate that into qt3 yourself (makefiles, etc.). 
it only works on linux and there's no gaurantee that trolltech will use the 
code. i just wanted to let you know that its done, and offers a little more 
functionality then before.

and no - you won't have to rewrite applications that already use QThread 
unless you use the QThread::current() method - which is recommended against.

here's what i did:

QThread changes:
	- rewrote internal state management
	- removed global thread list
	- replace QThread::current() with a method that actually
	  returns the current thread object instead of handle
	- rewrote QThread::exit to use a TLS representation of
	  the current thread (see QThread::current()).
	- default registration with global, default QThreadManager
	- added QThread::setManager(), QThread::getManager() to
	  allow migration of thread objects between QThreadManager's.
	- added QThread::setGroup(), QThread::getGroup() to
	  allow collection of threads into groups

QThreadManager
the thread manager is used as a single interface for managing either single 
threads, groups of threads or all threads for that manager.
	- single global instance
	- application specific QThreadManager's
	- can be used to wait on all threads
	- can be used to wait on groups of threads
	- can be used to wait on single thread

i would have added additional functionality like the ability to cancel
a thread/groups of threads/all threads and the same for signalling them,
suspending them and resuming them, but those capabilities aren't gauranteed 
across platforms (pthread doesn't support suspend/resume, windows doesn't 
support signal/cancel).

QThreadKey<T>
the QThreadKey is a typesafe wrapper for thread local storage (thread 
specific storage). essentially, you create the key as a static element of a 
class that that will be used inside a thread context and assign some value to 
it. currently, its being used inside Qt to hold a pointer to the current 
thread ( QThreadKey<QThread *> ).
	- automatic creation inside constructor
	- automatic deletion inside destructor
	- get()/set() to access or modifiy the value of the key.
	- will not automatically destroy pointers stored in the key.

hopefully, Qt will commit these changes to 3.1 or some near future version of 
qt. like i said before, if you're interested, let me know and i will send you 
the files that i changed/added. i won't post them to the list though, because 
its trolltech's decision on whether or not to use it. if you like the 
changes, write trolltech and let them know that you found them a) useful b) 
interesting c) stupid or d) lame.

also, if trolltech commits those changes, and i can find some spare time, i 
plan on writing a kthread library that implements some oo patterns found in 
the ACE toolkit for kde - specifically the active object stuff which is by 
far some of the coolest code i've ever seen. whether or not you find it 
useful is another story :)

thanks,

Andrew Sutton
ansutton@sep.com
 
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