[Spread-users] SP_join from different tread as SP_receive

John Schultz jschultz at spreadconcepts.com
Fri Jun 15 16:18:14 EDT 2007

Yes, you are mistaken. ;)

So long as you use a thread safe version of the client library a mailbox 
can be shared between multiple sending and multiple recieving threads, 
although the particular order of their sends/recvs is arbitrary, which can 
be particularly undesirable on receive.

You do need to be careful about closing/killing a mailbox though as you 
can cause a race condition if other connections are being created in 
parallel.  For example, a thread is using mailbox #X, another thread 
closes mailbox #X, (another thread) creates a new mailbox and the OS 
assigns it file descriptor #X and the original thread then uses mailbox #X 
oblivious to the fact that it actually is a different connection (e.g. - 
different private name, different group subscriptions, etc.).

Spread 4 will only close a mailbox/fd in response to a close or kill call 
from a user on it.  Spread 3 would close a mailbox/fd in response to any 
unrecoverable error on it.  So with Spread 3 there is an unavoidable race 
condition (if you are creating connections in parallel).


John Schultz
Spread Concepts
Phn: 443 838 2200

On Fri, 15 Jun 2007, Alec H. Peterson wrote:

> Hi John,
> --On June 15, 2007 16:01:02 -0400 John Schultz <jschultz at spreadconcepts.com> 
> wrote:
>> Spread is thread safe so long as you use the proper client library.
> Hmm, I thought a single mailbox wasn't valid across multiple threads, am I 
> mistaken?
> Alec

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