界: Time and State

分布式计算是关于时间和状态的。也就是说，为了让多个组件相互通信，必须共享状态，所有这些都需要时间。

大多数程序员都会将其工作拟人化。他们会让一个控制线程以同样的方式（他们必须自己完成工作时采取的方式）执行整个程序。然而，现代计算机不同任务之间切换得非常快，在多核、多 CPU 或分布式系统中，两个事件可能完全同时发生。程序员预期的程序执行过程与实际情况之间存在差距，即存在缺陷。这些缺陷与线程、流程、时间和信息之间的意外交互有关。这些交互是通过共享状态发生的：信号量、变量、文件系统，以及总而言之，可以存储信息的任何内容。

Code Correctness: Erroneous Synchronization

Abstract
如果线程向其他线程发出信号后并未解除锁定 mutex，则其他线程将保持锁定并继续等待 mutex。
Explanation
在线程向其他等待 mutex 的线程发出信号后，它必须调用 pthread_mutex_unlock() 来解除锁定 mutex，然后其他线程才能开始运行。如果发出信号的线程无法解除锁定 mutex，则在第二个线程中调用 pthread_cond_wait() 函数时不会返回任何值，该线程也将无法执行。

例 1：以下代码通过调用 pthread_cond_signal() 向其他等待 mutex 的线程发出信号，但无法解除锁定 mutex，而其他线程会继续等待 mutex。


   ...
   pthread_mutex_lock(&count_mutex);

   // Signal waiting thread
   pthread_cond_signal(&count_threshold_cv);
   ...
References
[1] Standards Mapping - CIS Azure Kubernetes Service Benchmark 1
[2] Standards Mapping - CIS Amazon Elastic Kubernetes Service Benchmark 2
[3] Standards Mapping - CIS Amazon Web Services Foundations Benchmark 1
[4] Standards Mapping - CIS Google Kubernetes Engine Benchmark normal
[5] Standards Mapping - Common Weakness Enumeration CWE ID 373
[6] Standards Mapping - DISA Control Correlation Identifier Version 2 CCI-001094
[7] Standards Mapping - Motor Industry Software Reliability Association (MISRA) C Guidelines 2012 Rule 1.3
[8] Standards Mapping - NIST Special Publication 800-53 Revision 4 SC-5 Denial of Service Protection (P1)
[9] Standards Mapping - NIST Special Publication 800-53 Revision 5 SC-5 Denial of Service Protection
[10] Standards Mapping - OWASP Top 10 2004 A9 Application Denial of Service
[11] Standards Mapping - Payment Card Industry Data Security Standard Version 1.1 Requirement 6.5.9
[12] Standards Mapping - Security Technical Implementation Guide Version 3.1 APP6080 CAT II
[13] Standards Mapping - Security Technical Implementation Guide Version 3.4 APP6080 CAT II
[14] Standards Mapping - Security Technical Implementation Guide Version 3.5 APP6080 CAT II
[15] Standards Mapping - Security Technical Implementation Guide Version 3.6 APP6080 CAT II
[16] Standards Mapping - Security Technical Implementation Guide Version 3.7 APP6080 CAT II
[17] Standards Mapping - Security Technical Implementation Guide Version 3.9 APP6080 CAT II
[18] Standards Mapping - Security Technical Implementation Guide Version 3.10 APP6080 CAT II
[19] Standards Mapping - Security Technical Implementation Guide Version 4.1 APSC-DV-002400 CAT II
[20] Standards Mapping - Security Technical Implementation Guide Version 4.2 APSC-DV-002400 CAT II
[21] Standards Mapping - Security Technical Implementation Guide Version 4.3 APSC-DV-002400 CAT II
[22] Standards Mapping - Security Technical Implementation Guide Version 4.4 APSC-DV-002400 CAT II
[23] Standards Mapping - Security Technical Implementation Guide Version 4.5 APSC-DV-002400 CAT II
[24] Standards Mapping - Security Technical Implementation Guide Version 4.6 APSC-DV-002400 CAT II
[25] Standards Mapping - Security Technical Implementation Guide Version 4.7 APSC-DV-002400 CAT II
[26] Standards Mapping - Security Technical Implementation Guide Version 4.8 APSC-DV-002400 CAT II
[27] Standards Mapping - Security Technical Implementation Guide Version 4.9 APSC-DV-002400 CAT II
[28] Standards Mapping - Security Technical Implementation Guide Version 4.10 APSC-DV-002400 CAT II
[29] Standards Mapping - Security Technical Implementation Guide Version 4.11 APSC-DV-002400 CAT II
[30] Standards Mapping - Security Technical Implementation Guide Version 5.1 APSC-DV-002400 CAT II
[31] Standards Mapping - Security Technical Implementation Guide Version 5.2 APSC-DV-002400 CAT II
[32] Standards Mapping - Security Technical Implementation Guide Version 5.3 APSC-DV-002400 CAT II, APSC-DV-002950 CAT II
[33] Standards Mapping - Web Application Security Consortium Version 2.00 Denial of Service (WASC-10)
[34] Standards Mapping - Web Application Security Consortium 24 + 2 Denial of Service
desc.structural.cpp.code_correctness_erroneous_synchronization