[Newbies] Acquiring lock, releasing in callback

Sebastian Nozzi sebnozzi at gmail.com
Fri Nov 2 18:24:00 UTC 2012


Didn't know it was so simple... I was kind of intimidated by "wait". Thought, well, that it suspended the thread no matter what.

Another question, out of curiosity:

Is it possible to have one thread wait for 2 other threads to finish? Would it also be solved with Semaphores like this?

s1 := Semaphore forMutualExclusion.
s2 := Semaphore forMutualExclusion.
[ s1 wait. do stuff .... s1 signal] fork.
[ s2 wait. do stuff ..... s2 signal ] fork.

s1 wait. 
s2 wait.
"Here we are sure the two other processes finished, kind of..."

Or is there a more "friendly" way? :-)

Thanks again!


> You could use a Semaphore directly:
> 	semaphore := Semaphore forMutualExclusion.
> and then
> 	semaphore wait "acquire lock"
> 	...
> 	semaphore signal "release lock"
>> I am aware or Monitor/Mutex critical:, but I am not sure I can use it in my case.
> Semaphore>>critical: simply does a wait and signal like above. But it ensures that if something goes wrong the semaphore is still signaled, so it's more easy to use.
> - Bert -
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