以下哪一项是错误的?
(A)内核不调度用户级线程。
(B)当一个用户级线程被阻塞时，其进程的所有其他线程都被阻塞。
(C)用户级线程之间的上下文切换比内核级线程之间的上下文切换更快。
(D)内核级线程不能共享代码段答案： (D)
解释：
| User level thread | Kernel level thread |
|---|---|
| User thread are implemented by user processes. | kernel threads are implemented by OS. |
| OS doesn’t recognized user level threads. | Kernel threads are recognized by OS. |
| Implementation of User threads is easy. | Implementation of Kernel thread is complicated. |
| Context switch time is less. | Context switch time is more. |
| Context switch requires no hardware support. | Hardware support is needed. |
| If one user level thread perform blocking operation then entire process will be blocked. | If one kernel thread perform blocking operation then another thread can continue execution. |
| Example : Java thread, POSIX threads. | Example : Window Solaris. |
资料来源：https://www.geeksforgeeks.org/difference-between-user-level-thread-and-kernel-level-thread/
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