This section describes the ALMOS-MKH implementation of the POSIX compliant, user-level synchronisation services: mutex, condvar, barrier and semaphore.

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== A) General Principles ==

All data structure defined by  ALMOS-MKH to support the user-level, POSIX compliant, synchronization services are fully specific, and do NOT use the kernel level synchronization primitives described in section. does NOT use the  

== B) Mutex ==

 This file defines an user level POSIX compliant mutex.
 *
 * It can be used by muti-threaded user applications to synchronise user threads
 * running in different clusters.
 *
 * A mutex is declared by a given user process as a "pthread_mutex_t" global variable.
 * This user type is implemented as an unsigned long, but the value is not used by the 
 * kernel. ALMOS-MKH uses only the mutex virtual address as an identifier.
 * For each user mutex, ALMOS-MKH creates a kernel "remote_mutex_t" structure,
 * dynamically allocated in the reference cluster by the remote_mutex_create() function, 
 * and destroyed by the remote_mutex_destroy() function, using RPC if the calling thread
 * is not running in the reference cluster. 
 *
 * The blocking "remote_mutex_lock()" function implements a descheduling policy when
 * the lock is already taken by another thread : the calling thread is registered 
 * in a waiting queue, rooted in the mutex structure, and the the calling thread 
 * is blocked on the THREAD_BLOCKED_MUTEX condition. 
 * The "remote_mutex_unlock()" function unblocks the first waiting thread in the queue
 * without releasing the mutex if queue is not empty.

== C) Condvar ==

== D) Semaphore ==

== E) Barrier ==