oes a message queue need a mutex

[khlitoshi]

hi everyone,

does a message queue need to be acceded exclusively by processes ?

thanks to all of u

[wje_lf]

I'm not sure what your question means, but I'll try to answer it anyway.

If you have two processes which are trying to write messages to the same POSIX message queue at the same time, this will work properly. You do not need to coordinate things so that only one process at a time writes a message to that queue.

The same goes for reading. If you have two processes which are trying to read messages from the same POSIX message queue at the same time, this will work properly. One process will get one message and the other process will get another (if there are two messages waiting). You do not need to coordinate things so that only one process at a time reads a message from that queue.

Is this what you meant?

[khlitoshi]

thank you , it's exactly what i was looking for;

[khlitoshi]

but please take a look at this site, i think you're wrong;
Method for implementing a multiprocessor message queue without use of mutex gate objects - Patent 20060048162

[wje_lf]

If there's anything unique involved with that patent, it's not that the proposed mechanism claims to provide automatic mutual exclusion. It's that the proposed mechanism claims to provide more efficient automatic mutual exclusion:

The conditional atomic counters control access to a message queue or memory space in a simple and reliable manner while minimizing the overhead of access to the mutex gate objects typically used in the implementation of message queues of the prior art.

[khlitoshi]

thanks to take a look, because i'm not very good in english, but now i'm sure,