pthread_spin_init(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

PTHREAD_SPIN_INIT(3)    Linux Programmer's Manual   PTHREAD_SPIN_INIT(3)

NAME         top

       pthread_spin_init, pthread_spin_destroy - initialize or destroy a
       spin lock

SYNOPSIS         top

       #include <pthread.h>

       int pthread_spin_init(pthread_spinlock_t *lock, int pshared);
       int pthread_spin_destroy(pthread_spinlock_t *lock);

       Compile and link with -pthread.

   Feature Test Macro Requirements for glibc (see
   feature_test_macros(7)):

       pthread_spin_init(), pthread_spin_destroy():
           _POSIX_C_SOURCE >= 200112L

DESCRIPTION         top

       General note: Most programs should use mutexes instead of spin
       locks.  Spin locks are primarily useful in conjunction with real-
       time scheduling policies.  See NOTES.

       The pthread_spin_init() function allocates any resources required
       for the use of the spin lock referred to by lock and initializes
       the lock to be in the unlocked state.  The pshared argument must
       have one of the following values:

       PTHREAD_PROCESS_PRIVATE
              The spin lock is to be operated on only by threads in the
              same process as the thread that calls pthread_spin_init().
              (Attempting to share the spin lock between processes
              results in undefined behavior.)

       PTHREAD_PROCESS_SHARED
              The spin lock may be operated on by any thread in any
              process that has access to the memory containing the lock
              (i.e., the lock may be in a shared memory object that is
              shared among multiple processes).

       Calling pthread_spin_init() on a spin lock that has already been
       initialized results in undefined behavior.

       The pthread_spin_destroy() function destroys a previously
       initialized spin lock, freeing any resources that were allocated
       for that lock.  Destroying a spin lock that has not been
       previously been initialized or destroying a spin lock while
       another thread holds the lock results in undefined behavior.

       Once a spin lock has been destroyed, performing any operation on
       the lock other than once more initializing it with
       pthread_spin_init() results in undefined behavior.

       The result of performing operations such as pthread_spin_lock(3),
       pthread_spin_unlock(3), and pthread_spin_destroy() on copies of
       the object referred to by lock is undefined.

RETURN VALUE         top

       On success, there functions return zero.  On failure, they return
       an error number.  In the event that pthread_spin_init() fails,
       the lock is not initialized.

ERRORS         top

       pthread_spin_init() may fail with the following errors:

       EAGAIN The system has insufficient resources to initialize a new
              spin lock.

       ENOMEM Insufficient memory to initialize the spin lock.

VERSIONS         top

       These functions first appeared in glibc in version 2.2.

CONFORMING TO         top

       POSIX.1-2001.

       Support for process-shared spin locks is a POSIX option.  The
       option is supported in the glibc implementation.

NOTES         top

       Spin locks should be employed in conjunction with real-time
       scheduling policies (SCHED_FIFO, or possibly SCHED_RR).  Use of
       spin locks with nondeterministic scheduling policies such as
       SCHED_OTHER probably indicates a design mistake.  The problem is
       that if a thread operating under such a policy is scheduled off
       the CPU while it holds a spin lock, then other threads will waste
       time spinning on the lock until the lock holder is once more
       rescheduled and releases the lock.

       If threads create a deadlock situation while employing spin
       locks, those threads will spin forever consuming CPU time.

       User-space spin locks are not applicable as a general locking
       solution.  They are, by definition, prone to priority inversion
       and unbounded spin times.  A programmer using spin locks must be
       exceptionally careful not only in the code, but also in terms of
       system configuration, thread placement, and priority assignment.

SEE ALSO         top

       pthread_mutex_init(3), pthread_mutex_lock(3),
       pthread_spin_lock(3), pthread_spin_unlock(3), pthreads(7)

COLOPHON         top

       This page is part of release 5.13 of the Linux man-pages project.
       A description of the project, information about reporting bugs,
       and the latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.

Linux                          2021-03-22           PTHREAD_SPIN_INIT(3)

Pages that refer to this page: pthread_spin_lock(3)pthreads(7)