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.
Applications using this function may be subject to priority inversion, as
discussed in the Base Definitions volume of
IEEE Std 1003.1-2001, Section 3.285, Priority Inversion.
The pthread_spin_lock() and pthread_spin_trylock() functions are
part of the Spin Locks option and need not be provided on all implementations.
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html