Changes between Version 9 and Version 10 of user_synchro


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Timestamp:
Oct 9, 2018, 7:49:23 PM (3 years ago)
Author:
alain
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  • user_synchro

    v9 v10  
    1 This section describes the ALMOS-MKH implementation of the POSIX compliant, user-level synchronisation services: mutex, condvar, barrier and semaphore.
     1This section describes the ALMOS-MKH implementation of 4 POSIX compliant, user-level synchronisation services: mutex, condvar, barrier and semaphore.
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    2727 * The '''remote_mutex_create()''' function allocates and initializes a mutex, using an RPC if if the calling thread is not running in the reference cluster.
    2828 * The '''remote_mutex_destroy()''' function destroys a given mutex, using RPC if the calling thread is not running in the reference cluster.
    29  * The blocking '''remote_mutex_lock()''' function implements a descheduling policy when the mutex is already taken by another thread : the calling thread registers in the mutex waiting queue, and blocks on THREAD_BLOCKED_USERSYNC.
     29 * The blocking '''remote_mutex_lock()''' function implements a descheduling policy when the mutex is already taken by another thread : the calling thread registers in the mutex waiting queue, and blocks on the THREAD_BLOCKED_USERSYNC condition.
    3030 * The '''remote_mutex_unlock()''' function unblocks the first waiting thread in the queue, without releasing the mutex, if the queue is not empty.
    3131
     
    4242 * The '''remote_condvar_create()''' function allocates and initializes a condvar, using an RPC if if the calling thread is not running in the reference cluster.
    4343 * The '''remote_condvar_destroy()''' function destroys a given condvar, using RPC if the calling thread is not running in the reference cluster.
    44  * The blocking '''remote_condvar_wait()''' function allows the calling thread to block on THREAD_BLOCKED_USERSYNC, and to register in the condvar waiting queue.
     44 * The blocking '''remote_condvar_wait()''' function implement a descheduling policy: the calling thread registers in the condvar waiting queue, and  blocks on the THREAD_BLOCKED_USERSYNC condition.
    4545 * The '''remote_condvar_signal()''' function allows (another) thread to unblock the first blocked thread waiting on a given condvar.
    4646 * The '''remote_condvar_broadcast()''' function allows (another) thread to unblock all threads waiting on a given condvar.
     
    5151The user level, POSIX compliant, barrier is defined in the '''pthread''' library, implemented by the [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/libs/libpthread/pthread.h pthread.h] and [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/libs/libpthread/pthread.c pthread.c] files.
    5252
    53 It can be used by a muti-threaded user application to implement a "rendez-vous" for a given number of  threads running in different clusters.
     53It can be used by a muti-threaded user application to implement a "rendez-vous" for a given number of  threads running in different clusters. As the implementation uses a toggle variable, the same barrier can be safely used several times, as long as the number of expected threads does not change.
    5454
    5555The kernel implementation of a barrier is defined in the [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/libk/remote_barrier.h remote_barrier.h] and [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/libk/remote_barrier.c remote_barrier.c] files.
     
    5858 * The '''remote_barrier_create()''' function allocates and initializes a barrier, using an RPC if if the calling thread is not running in the reference cluster.
    5959 * The '''remote_barrier_destroy()''' function destroys a given barrier, using RPC if the calling thread is not running in the reference cluster.
    60  * The blocking '''remote_barrier_wait()''' function returns only when all expected threads (defined by the remote_barrier_create() function) reach the barrier. As the implementation uses a toggle variable, this barrier can be safely called several times, as long as the number of expected threads does not change.
     60 * The blocking '''remote_barrier_wait()''' function returns only when all expected threads (defined by the remote_barrier_create() function) reach the barrier. It implement a descheduling policy: when a thread is not the last expected thread, it register in he barrier waiting queue and blocks on the THREAD_BLOCKED_USERSYNC condition. The last thread reset the barrier and unblocks all waiting threads.
    6161
    6262== E) Semaphore ==
     
    7171 * The '''remote_sem_create()''' function allocates and initializes a semaphore, using an RPC if if the calling thread is not running in the reference cluster.
    7272 * The '''remote_sem_destroy()''' function destroys a given semaphore, using RPC if the calling thread is not running in the reference cluster.
    73  * The blocking '''remote_sem_wait()''' function returns only when the semaphore has a non-zero value, and has been atomically decremented. If the semaphore has a zero value, the calling thread registers in the semaphore  waiting queue, and block on THREAD_BLOCKED_USERSYNC.
     73 * The blocking '''remote_sem_wait()''' function returns only when the semaphore has a non-zero value, and has been atomically decremented. If the semaphore has a zero value, the calling thread registers in the semaphore  waiting queue, and block on the THREAD_BLOCKED_USERSYNC condition.
    7474 * The '''remote_sem_post()''' function  atomically increments the semaphore. If the waiting queue is not empty, it unblock all waiting threads.
    7575 * The '''remote_sem_get_value()''' function returns the semaphore current value, without modifying the semaphore state.