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Notes for lwp on top of pthreads
--------------------------------
The pthread-lwp implementation is compatible with the non-preemptive
lwp implementation. It even encapsulates enough of the `quirks' to
allow venus to run without problems.
New function
------------
void PRE_Concurrent(int on)
/* on != 0 : Take the calling thread out of the LWP runqueues and let it
* run concurrently.
* on == 0 : Return the calling thread under the reign of the big lock.
*/
Special notes
-------------
LWP RW-locks
Can safely be used by both concurrent and non-concurrent threads.
When locking, non-concurrent threads release the run_mutex.
LWP_QSignal/LWP_QWait
Implemented as a counting semaphore. No more lost signals, and
allows concurrent threads to use it without waiting for the run_mutex
(yielding non-concurrent threads). Non-concurrent threads release the
mutex while waiting.
LWP_SignalProcess/LWP_NoYieldSignal/LWP_MwaitProcess/LWP_WaitProcess
Concurrent threads need to aquire the run_mutex and will therefore
block until the current non-concurrent thread yields. This affects
both waiting and signalling threads.
Compiling
---------
All c/c++ code which will be linked against liblwp_pt has to be compiled
with -D_REENTRANT.
Future additions
----------------
IOMGR_Read/IOMGR_Write functions that release the run_mutex for
non-concurrent threads (simple, look at IOMGR_Select). But they should
then also be implemented as `polling' functions in the normal LWP
implementation.
For more information, read the source (lwp_pt.c, lock_pt.c, etc.) I've
tried to put in a lot of useful comments.
-- Jan
|
