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


pthread_spin_lock, pthread_spin_trylock, pthread_spin_unlock - lock and unlock a spin lock


#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);

Compile and link with -pthread.

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

pthread_spin_lock(), pthread_spin_trylock():

_POSIX_C_SOURCE >= 200112L


The pthread_spin_lock() function locks the spin lock referred to by lock. If the spin lock is currently unlocked, the calling thread acquires the lock immediately. If the spin lock is currently locked by another thread, the calling thread spins, testing the lock until it becomes available, at which point the calling thread acquires the lock.

Calling pthread_spin_lock() on a lock that is already held by the caller or a lock that has not been initialized with pthread_spin_init(3) results in undefined behavior.

The pthread_spin_trylock() function is like pthread_spin_lock(), except that if the spin lock referred to by lock is currently locked, then, instead of spinning, the call returns immediately with the error EBUSY.

The pthread_spin_unlock() function unlocks the spin lock referred to lock. If any threads are spinning on the lock, one of those threads will then acquire the lock.

Calling pthread_spin_unlock() on a lock that is not held by the caller results in undefined behavior.


On success, these functions return zero. On failure, they return an error number.


pthread_spin_lock() may fail with the following errors:

The system detected a deadlock condition.

pthread_spin_trylock() fails with the following errors:

The spin lock is currently locked by another thread.


These functions first appeared in glibc in version 2.2.




Applying any of the functions described on this page to an uninitialized spin lock results in undefined behavior.

Carefully read NOTES in pthread_spin_init(3).


pthread_spin_destroy(3), pthread_spin_init(3), pthreads(7)


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2021-03-22 Linux