POSIX deadlock detection: A walk through linux kernel source

A note to readers: The following content is completely oriented for developers, especially in C. In case you find it difficult to understand certain terms, please help yourselves to google around and understand the concepts. I have tried including links wherever necessary in order to effectively interpret the article(see provided links towards the end). Last but not least, as per POSIX documentation[1], deadlock detection is guaranteed for locks between different processes and not between different threads inside a process or between threads belonging to different processes.

As you can see from the heading of this article, I am aiming at explaining the source code for detecting POSIX deadlocks. Before that let me quickly brief the concept of deadlock in operating systems. A deadlock is a situation where two processes sharing the same resource are preventing each other from accessing the resource which will result in an undefined wait for those resources. Following are the four necessary conditions(Coffman conditions)[2] which leads to a deadlock scenario:

* Mutual exclusion
* Hold and Wait
* No pre-emption
* Circular wait

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