The pth environment is a cooperative model. This means that there is only one "real" thread in which all the others are emulated. If one of the pth-threads no longer needs the cpu, for example because it is put to sleep for some time, it has to return the control to the pth subsystem which will continue execution with another waiting pth-thread.
However if you block your "real" thread by calling a blocking function like "sleep", "select", "read", etc. the entire program will be halted. This is why each blocking function has an implementation within the pth library. These functions are named after their original ones like "pth_sleep", "pth_select", and so on. The replacement functions will handle blocking calls in a special way to make sure that the other pth-treads will continue to work. So, if you want to use the pth library you should make sure, you don't block your program, by always calling the replacement function if available. And if you have code which will take a long time to execute, you should insert calls to pth_yield. Otherwise this pth-thread will never return control to the pth subsystem and this will block the other threads. About your first testing program: You created a thread and then you start writing "o"s. Unfortunately you call "sleep" instead of "pth_sleep". Your main thread will block the entire program each time for one second and because the pth subsystem is never executed, the other thread will never be executed as well. The reason why you never saw any "." may be because you called pthread_join instead of pth_join. But this is only a wild guess, because you posted the pthread version of your test program. However if you call pth_join the execution of the main thread will be suspended and the pth subsystem will execute the other thread. This thread is not cooperative as well because you built the same "busy" loop which will never return execution to the pth subsystem but this doesn't matter because your main thread is already almost done. The same applies to your second example. If you call "select" and "accept" you can be sure your program blocks and the other threads will never be executed. Regards Marc On Fri, Oct 04, 2002 at 12:14:13PM +0200, Terry wrote: > ive found that out already, but what i was tryin to do was to show > that somethings wrong with pth's pthread lib. > > i tried a few pthreaded programs and they all have problems with pth. > the prog i pasted here has only unparalleled output, but take this > one followed for example. > it wont even open a socket! and this time it doesnt look like > a serialization problem does it ? > > what might be wrong with this one ? > also tested on openbsd and redhat linux. > > thanks again in advance, > terry
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