# os_unfair_lock_trylock Locks an unfair lock if it is not already locked. ``` extern bool os_unfair_lock_trylock(os_unfair_lock_t lock); ``` ## Parameters `lock` A pointer to the unfair lock to be locked. ## Return Value `true` if the lock was successfully locked, or `false` if the lock was already locked. ## Discussion If this function returns `false`, you must either proceed without having acquired the lock or call [`os_unfair_lock_lock`](/documentation/os/os_unfair_lock_lock) directly. Do not attempt to call this function within a retry loop; [`os_unfair_lock_lock`](/documentation/os/os_unfair_lock_lock) accomplishes the same task, without hiding the lock waiter from the system or preventing resolution of priority inversions. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)