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Re: Threading synchronization: does a primitive exists?
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Re: Threading synchronization: does a primitive exists?


  • Subject: Re: Threading synchronization: does a primitive exists?
  • From: Ken Thomases <email@hidden>
  • Date: Thu, 05 May 2011 09:22:08 -0500

On May 5, 2011, at 8:51 AM, eveningnick eveningnick wrote:

> 2011/5/5 Heath Borders <email@hidden>:
>> Try NSConditionLock. Its documentation should be pretty self-explanatory.
>>
>
> Health,
> thanks for the response.
> However, i can't see how can i use NSConditionLock in my situation.
> For every lock (or mutex/semaphore - which essentially is the same) i
> need to acquire it 1 time at least to stop the the thread when a
> second attempt to acquire it from a different thread is made.
> What i need - is to stop the thread A immediately after the thread B
> has been spawned by a thread A. I am afraid if i acquire the lock from
> A, and then acquire it as soon as B starts (in B routine), the thread
> A may even finish before the thread B _actually_ starts (or rather B's
> threadfunction starts executing).
> Am i wrong somewhere here?

NSConditionLock allows one to lock waiting for specific conditions.  The lock can be created in an initial condition, say THREAD_B_NOT_RUNNING.  Then, Thread A can spawn B and lock waiting for condition THREAD_B_RUNNING.  Thread B can take the lock unconditionally and, when it's ready, unlock it with condition THREAD_B_RUNNING.  Or whatever.

Other possible techniques include using a pipe to send a signal byte from one thread to the other.  So, thread A would do a blocking read from the pipe.  Thread B would write a single byte to the pipe to signal whatever condition.

There are all sorts of other approaches.

Regards,
Ken

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    • Re: Threading synchronization: does a primitive exists?
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References: 
 >Threading synchronization: does a primitive exists? (From: eveningnick eveningnick <email@hidden>)
 >Re: Threading synchronization: does a primitive exists? (From: Heath Borders <email@hidden>)
 >Re: Threading synchronization: does a primitive exists? (From: eveningnick eveningnick <email@hidden>)

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