[linrad] Re: Error exit

[<leif@xxxxxxxxxx>]

Hi Frank,

> The proper way to shut them down is with pthread_cancel(), 
> one for each thread.
Hmmm, this is what I do now - and find complicated during 
the transition from a single thread to a multi-threaded
structure.....

> If you cancel a thread that has been started with default 
> parameters, it will be cancelled either at a convenient 
> point (such as when it attempts to acquire a mutex or 
> semaphore) or at point of your own choosing, via 
> pthread_testcancel().
Ok, what about threads waiting for keyboard, mouse events,
network input or other I/O functions?
I have set the parameters for CANCEL_ASYNCHRONOUS and
put start and stop of hardware drivers in the main routine.
Do you see any problem with that?

> Usually the threads are started from a main routine, which 
> proceeds to do a pthread_join() for each of the threads it's 
> started. When threads are cancelled they exit cleanly to the 
> corresponding pthread_join() points.
What about threads that do not exit explicitly, the ones
killed by pthread_cancel() from the thread having the thread
killing as its single task?
It it safe to join only the thread that has killed all the others?
There are many different modes of operation with different threads 
running and it would be nice to not have to keep track of everything
under error exit conditions;-)

Ctrl C is doing something, is it impossible to do the same from
within an arbitrary thread within the program?

> One thing this means is that there probably needs to be a 
> single thread whose task is to shut down the other threads. 
> It alone does a pthread_exit() which returns to a 
> pthread_join() point.
What happens if I join threads that have already been killed?
(In case it is unsafe to join only the "kill everything" thread?
The code is intended to be portable to MS Windows and
Macintosch...

73

Leif / SM5BSZ
 


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