synchronized->objc_sync_enter/objc_sync_exit

objc_sync_enter：

递归锁，与objc_sync_exit配合使用，注意死锁

  • Begin synchronizing on ‘obj’. Allocates recursive pthread_mutex associated with ‘obj’ if needed.
  • Parameters obj The object to begin synchronizing on.
  • Returns OBJC_SYNC_SUCCESS once lock is acquired.

objc_sync_exit

  • End synchronizing on ‘obj’.
  • Parameters obj The object to end synchronizing on.
  • Returns OBJC_SYNC_SUCCESS or OBJC_SYNC_NOT_OWNING_THREAD_ERROR

三.示例

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  let lockValue = 0
  objc_sync_enter(lockValue)
       //执行代码块
  objc_sync_exit(lockValue)