5.5.1 THREADPRIVATE and Thread-Specific Information

When a thread encounters a task scheduling point, the implementation may choose to suspend the current task and schedule the thread to work on another task. This implies that the value of a threadprivate variable, or other thread-specific information such as the thread number, may change across a task scheduling point.

If the suspended task is tied, then the thread that resumes executing the task will be the same thread that suspended it. Therefore, the thread number will remain the same after the task is resumed. However, the value of a threadprivate variable may change because the thread may have been scheduled to work on another task that modified the threadprivate variable before resuming the suspended task.

If the suspended task is untied, then the thread that resumes executing the task may be different from the thread that suspended it. Therefore, both the thread number and the value of a threadprivate variable before and after the task scheduling point may be different.