[M] Change in osmo-ttcn3-hacks[master]: library: add generic Mutex API for parallel components - gerrit-log

20 Sep 2024

Attention is currently required from: fixeria, laforge.

pespin has posted comments on this change by fixeria. (
https://gerrit.osmocom.org/c/osmo-ttcn3-hacks/+/38206?usp=email )

Change subject: library: add generic Mutex API for parallel components
......................................................................

Patch Set 2:

(1 comment)

File library/Mutex.ttcn:

https://gerrit.osmocom.org/c/osmo-ttcn3-hacks/+/38206/comment/47ac92a8_0632…
:
PS2, Line 19: 	port MutexPT LOCK;	/* port for LOCKing the mutex */
...
  But why would you want to lock the Mutex twice? Is
this a normal scenario? 
Sure reentrant mutexes are a thing :) This is usually only needed in more complex
scenarios than what we aim here though.
This can be used for instance to implement semaphores, which eg. allow up to N-concurrent
users where N can be defined.

...
  Can you explain your idea a bit more? 
Yes, you have 1 port which has LOCK and UNLOCK operations.

	alt {
	[lock_count == 0] pt.get_call(LOCK) -> sender {
	   lock_sender = sender;
	   lock_count++;
	   pt.send_response(sender, LOCK);
	}
	[lock_count > 0] pt.get_call(LOCK) -> sender {
	   if (lock_count > 0) {
		   if(and sender != lock_sender) {
			  error();
		  } else {
			  /* Make the component wait until mutex is unlocked: */
			  lock_queue := lock_queue & { sender };
			  return;
		  }
	   lock_sender = sender;
	   lock_count++;
	   pt.send_response(sender, LOCK);
	}
	[lock_count == 0] pt.get_call(UNLOCK) -> sender {
	   errror();
	}
	[lock_count > 0] pt.get_call(UNLOCK) -> sender {
	   if (sender != lock_sender)
		   error();
	   lock_count--;
	   pt.send_response(sender, UNLOCK);
	   if (lock_count == 0) {
		   if (lengthof(lock_queue) > 0)
			  sender := lock_queue[0]
			  //TODO: HERE pop lock_queue[0] from queue
			  /* Tell first component waiting in the queue that it finally acquired the lock: */
			  pt.send_response(sender, LOCK);
			  lock_count++;
	   }
	}

	}

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Gerrit-MessageType: comment
Gerrit-Project: osmo-ttcn3-hacks
Gerrit-Branch: master
Gerrit-Change-Id: Id71f43bd5fc78d4bb4417d6c01fcff8112ea6032
Gerrit-Change-Number: 38206
Gerrit-PatchSet: 2
Gerrit-Owner: fixeria &lt;vyanitskiy(a)sysmocom.de&gt;
Gerrit-Reviewer: Jenkins Builder
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