signaling a thread to stop

signaling a thread to stop

[David Eduardo Gomez Noguera]

Hello.
I am writting a gtk program that comunicates with a pen pad. when it
starts writting, it starts doing it in "real time", just as the pen
moves, there is flow of data, so a toggle button creates a thread, and
will need to stop it too.

what is the best way to do it?

i read on libc info page pthread_cancel, but didnt understand what does
it exactly do.
I think it signals the thread, then the thread must tests its value to
see if it has been "canceled" and decide upon an action (after the
thread itself was set to CANCEL_ENABLE)what to do, am i right?

the thread needs to stop comunication with the pad, so it does not keep
sending data, and then flush any remaining data when asked to stop. And
unlock a mutex.

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Re: signaling a thread to stop

[Glynn Clements]

David Eduardo Gomez Noguera wrote:

> I am writting a gtk program that comunicates with a pen pad. when it
> starts writting, it starts doing it in "real time", just as the pen
> moves, there is flow of data, so a toggle button creates a thread, and
> will need to stop it too.
> 
> what is the best way to do it?
> 
> i read on libc info page pthread_cancel, but didnt understand what does
> it exactly do.
> I think it signals the thread, then the thread must tests its value to
> see if it has been "canceled" and decide upon an action (after the
> thread itself was set to CANCEL_ENABLE)what to do, am i right?

Assuming that the thread has cancellation enabled (which is the
default), if the cancellation type is deferred (the default), it will
be cancelled upon the next call to any of:

       pthread_join
       pthread_cond_wait
       pthread_cond_timedwait
       pthread_testcancel
       sem_wait
       sigwait

OTOH, if the cancellation type is set to asynchronous, with
pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS), the thread will be
terminated as soon as it receives the request.

-- 
Glynn Clements <glynn.clements@virgin.net>