CODEWITHSUNDEEP
processerlangmessaging
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Reputation: 3070

Do you risk triggering race conditions when sending large messages in Erlang?

In Erlang if two processes A and B are sending message to a process C simultaneously. Will there be a race condition?

Will C receive the complete message from A and then proceed for the message from B? or is it that C is likely be going to receive chunks of A's message along with chunks of B's message?

Upvotes: 4

Views: 415

Answers (1)

Hynek -Pichi- Vychodil
Hynek -Pichi- Vychodil

Reputation: 26121

Message receiving is an atomic operation.

If you are interested how it is done, read the source code of VM. If I simplify it, the sending process is doing those steps:

  1. Allocate a target memory space in the sending process (it's called environment).
  2. Copy the message to that memory space
  3. Take the external lock on the target process
  4. Link message into the mailbox linked list
  5. Release the external lock on the target process

As you can see, copying is done outside (before) critical section and the critical section is pretty fast. It is just juggling with few pointers.

Upvotes: 5

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