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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON |
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PTHREAD_SPIN_INIT(3) Linux Programmer's Manual PTHREAD_SPIN_INIT(3)
pthread_spin_init, pthread_spin_destroy - initialize or destroy a
spin lock
#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
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(3) on copies of the
object referred to by lock is undefined.
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.
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.
These functions first appeared in glibc in version 2.2.
POSIX.1-2001.
Support for process-shared spin locks is a POSIX option. The option
is supported in the glibc implementation.
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.
pthread_mutex_init(3), pthread_mutex_lock(3), pthread_spin_lock(3),
pthread_spin_unlock(3), pthreads(7)
This page is part of release 4.15 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 2017-09-30 PTHREAD_SPIN_INIT(3)
Pages that refer to this page: pthread_spin_init(3), pthread_spin_lock(3), pthreads(7)
Copyright and license for this manual page
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