---
name: "pthread_spin_lock"
section: "3"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/pthread_spin_lock"
---

# pthread\_spin\_lock(3)

lock or unlock a spin lock

## NAME

**pthread\_spin\_lock**, **pthread\_spin\_trylock**, **pthread\_spin\_unlock** – lock or unlock a spin lock

## LIBRARY

POSIX Threads Library (libpthread, -lpthread)

## SYNOPSIS

**#include \<pthread.h\>**

*int*\

**pthread\_spin\_lock**(*pthread\_spinlock\_t \*lock*);

*int*\

**pthread\_spin\_trylock**(*pthread\_spinlock\_t \*lock*);

*int*\

**pthread\_spin\_unlock**(*pthread\_spinlock\_t \*lock*);

## DESCRIPTION

The **pthread\_spin\_lock**() function will acquire *lock* if it is not currently owned by another thread. If the lock cannot be acquired immediately, it will spin attempting to acquire the lock (it will not sleep) until it becomes available.

The **pthread\_spin\_trylock**() function is the same as **pthread\_spin\_lock**() except that if it cannot acquire *lock* immediately it will return with an error.

The **pthread\_spin\_unlock**() function will release *lock*, which must have been previously locked by a call to **pthread\_spin\_lock**() or **pthread\_spin\_trylock**().

## RETURN VALUES

If successful, all these functions will return zero. Otherwise, an error number will be returned to indicate the error.

None of these functions will return EINTR.

## ERRORS

The **pthread\_spin\_lock**(), **pthread\_spin\_trylock**() and **pthread\_spin\_unlock**() functions will fail if:

- \[EINVAL\]

  The value specified by *lock* is invalid or is not initialized.

The **pthread\_spin\_lock**() function may fail if:

- \[EDEADLK\]

  The calling thread already owns the lock.

The **pthread\_spin\_trylock**() function will fail if:

- \[EBUSY\]

  Another thread currently holds *lock*.

The **pthread\_spin\_unlock**() function may fail if:

- \[EPERM\]

  The calling thread does not own *lock*.

## SEE ALSO

[pthread\_spin\_destroy(3)](/pthread_spin_destroy/3.md), [pthread\_spin\_init(3)](/pthread_spin_init/3.md)

## HISTORY

The **pthread\_spin\_lock**(), **pthread\_spin\_trylock**() and **pthread\_spin\_unlock**() functions first appeared in library “libkse” in FreeBSD 5.2, and in library “libthr” in FreeBSD 5.3.

## BUGS

The implementation of **pthread\_spin\_lock**(), **pthread\_spin\_trylock**() and **pthread\_spin\_unlock**() is expected to conform to IEEE Std 1003.2 (“POSIX.2”).