# Lec08 A section of code we don't want interrupted by certain other code is a "critical section". Want atomicity and consistency. Lock: Lock rules: acquire and release. Between acquire and release, a lock is held by the thread that acquire it. A lock may only be held by one thread at a time. If T2 wants to acquire a lock held by T1, T2 blocks until T1 release it. Def: fine-grained locking - only hold the lock for a small piece of work coarse-grained locking. (don't release if you immediately want to require) Deadlock: exception, no release. Try to acquire lock but the other was not released. with staement calls (to avoid exception not release lock) with lock: --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://tianyi0216.gitbook.io/blog/course_notes/544-notes/lec08.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.