pthread_spin_destroy

Synopsis

#include <pthread.h>

int pthread_spin_destroy(pthread_spinlock_t *lock);

int pthread_spin_init(pthread_spinlock_t *lock, int pshared);

Status

Implemented

Conformance

IEEE Std 1003.1-2017

Description

The pthread_spin_destroy() function shall destroy the spin lock referenced by lock and release any resources used by the lock. The effect of subsequent use of the lock is undefined until the lock is reinitialized by another call to pthread_spin_init(). The results are undefined if pthread_spin_destroy() is called when a thread holds the lock, or if this function is called with an uninitialized thread spin lock.

The pthread_spin_init() function shall allocate any resources required to use the spin lock referenced by lock and initialize the lock to an unlocked state. In Phoenix-RTOS a spin lock is a single integer updated with atomic operations and needs no other resources.

The supported value of pshared is PTHREAD_PROCESS_PRIVATE (see POSIX deviations).

The results are undefined if pthread_spin_init() is called specifying an already initialized spin lock. The results are undefined if a spin lock is used without first being initialized.

If the pthread_spin_init() function fails, the lock is not initialized and the contents of lock are undefined.

Only the object referenced by lock may be used for performing synchronization. The result of referring to copies of that object in calls to pthread_spin_destroy(), pthread_spin_lock(), pthread_spin_trylock(), or pthread_spin_unlock() is undefined.

Return value

Upon successful completion, these functions shall return zero; otherwise, an error number shall be returned to indicate the error.

Errors

The pthread_spin_init() function shall fail if:

  • EAGAIN - The system lacks the necessary resources to initialize another spin lock.

  • ENOMEM - Insufficient memory exists to initialize the lock.

  • EINVAL - The value of pshared is neither PTHREAD_PROCESS_PRIVATE nor PTHREAD_PROCESS_SHARED.

  • ENOTSUP - The value of pshared is PTHREAD_PROCESS_SHARED (see POSIX deviations).

These functions shall not return an error code of EINTR.

POSIX deviations

With the Thread Process-Shared Synchronization option, IEEE Std 1003.1-2017 requires a spin lock initialized with PTHREAD_PROCESS_SHARED to be usable by any thread that has access to the memory where it is allocated, even if that memory is shared by multiple processes. Phoenix-RTOS does not support this option (_POSIX_THREAD_PROCESS_SHARED is not defined), and pthread_spin_init() returns ENOTSUP for PTHREAD_PROCESS_SHARED, an error that the standard does not define for it. Spin locks reject it consistently with the other synchronization objects, which are built on per-process kernel resources.