Inter-Process Mutexes

["Drake Baker" <drbtq at hotmail dot com>]

Gentlemen,

I have seen conflicting information on the web concerning inter-process 
mutexes in CYGWIN.  I have seen outright statements that it is not 
supported, and I have seen statements that ALL mutexes are inter-process by 
default.  Obviously, only one statement is currently correct.

The bottom line is that I have some shared memory and multiple processes -- 
basically a critical section.  I need a technique to implement the critical 
section, and preferably a solution that is portable.

I have tried for countless hours over the last few days before concluding 
that process shared mutexes don't exist in CYGWIN despite some google 
results implying they do.  (I hope I am wrong, and it does support them).

Any solution that will work in CYGWIN and a Linux box would be appreciated 
-- all I need is a critical section for mutliple processes.

Thank you in advance for your help!

-Drake

--- snippets for reference, in case my assumption is wrong (not actual code, 
simplified cuts)

... initializing
pthread_mutexattr_init(&mattr); // create default attributes, returns no 
error

pthread_mutexattr_setpshared(&mattr, PTHREAD_PROCESS_SHARED); // set for 
inter-process sharing (it is returning EINVAL)

pthread_mutex_init(&mutex, &mattr);  // init, returns no error

... locking/etc...

pthread_mutex_lock(&mutex) // returns no error in process that init'd mutex, 
EINVAL in other processes

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