The Open Group Base Specifications Issue 7
IEEE Std 1003.1-2008, 2016 Edition
Copyright © 2001-2016 The IEEE and The Open Group

#### NAME

> pthread_spin_lock, pthread_spin_trylock - lock a spin lock object

#### SYNOPSIS

> ``#include <pthread.h>
> int pthread_spin_lock(pthread_spinlock_t *`lock`);
> int pthread_spin_trylock(pthread_spinlock_t *`lock`);
> ``

#### DESCRIPTION

> The pthread_spin_lock() function shall lock the spin lock referenced by lock. The calling thread shall acquire the lock if it is not held by another thread. Otherwise, the thread shall spin (that is, shall not return from the pthread_spin_lock() call) until the lock becomes available. The results are undefined if the calling thread holds the lock at the time the call is made. The pthread_spin_trylock() function shall lock the spin lock referenced by lock if it is not held by any thread. Otherwise, the function shall fail.

> The results are undefined if any of these functions is called with an uninitialized spin lock.

#### 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_lock() function may fail if:

> [EDEADLK]
>   A deadlock condition was detected.

> The pthread_spin_trylock() function shall fail if:

> [EBUSY]
>   A thread currently holds the lock.

> These functions shall not return an error code of [EINTR].

The following sections are informative.

#### EXAMPLES

> None.

#### APPLICATION USAGE

> Applications using this function may be subject to priority inversion, as discussed in XBD Priority Inversion.

#### RATIONALE

> If an implementation detects that the value specified by the lock argument to pthread_spin_lock() or pthread_spin_trylock() does not refer to an initialized spin lock object, it is recommended that the function should fail and report an [EINVAL] error.

> If an implementation detects that the value specified by the lock argument to pthread_spin_lock() refers to a spin lock object for which the calling thread already holds the lock, it is recommended that the function should fail and report an [EDEADLK] error.

#### FUTURE DIRECTIONS

> None.

#### SEE ALSO

> pthread_spin_destroy, pthread_spin_unlock

> XBD Priority Inversion, Memory Synchronization, <pthread.h>

#### CHANGE HISTORY

> First released in Issue 6. Derived from IEEE Std 1003.1j-2000.

> In the SYNOPSIS, the inclusion of <sys/types.h> is no longer required.

> IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/107 is applied, updating the ERRORS section so that the [EDEADLK] error includes detection of a deadlock condition.

#### Issue 7

> The pthread_spin_lock() and pthread_spin_trylock() functions are moved from the Spin Locks option to the Base.

> The [EINVAL] error for an uninitialized spin lock object is removed; this condition results in undefined behavior.

> The [EDEADLK] error for a spin lock object for which the calling thread already holds the lock is removed; this condition results in undefined behavior.

End of informative text.

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