diff --git a/content/notes/20-sync-deadlock.md b/content/notes/20-sync-deadlock.md
new file mode 100644
index 000000000..5cc980937
--- /dev/null
+++ b/content/notes/20-sync-deadlock.md
@@ -0,0 +1,27 @@
+---
+title: "20-sync-deadlock"
+aliases: 
+tags: 
+- cosc204
+- lecture
+---
+
+# Bounded buffer problem
+![slide|400](https://i.imgur.com/tdAllKY.png)
+
+producer consumer problem
+
+issues
+- no data in buffe: consumer has nothing to consume
+- buffer is full: no space for producer to produce
+
+private vars
+- in: next pos in buf to be writted
+- out: next pos in buf to be read
+
+shared variables
+- buffer
+- counter: number of items in buffer
+
+waiting
+- busy"
\ No newline at end of file
diff --git a/content/notes/cosc-204.md b/content/notes/cosc-204.md
index 2c44e5809..f9ab8e5ad 100644
--- a/content/notes/cosc-204.md
+++ b/content/notes/cosc-204.md
@@ -49,7 +49,9 @@ tags:
 - [16-device-drivers](notes/16-device-drivers.md)
 - [17-processes-communication](notes/17-processes-communication.md)
 - [18-processes-sharing-and-threads](notes/18-processes-sharing-and-threads.md)
-- 
+- [19-cpu-scheduling](notes/19-cpu-scheduling.md)
+
+
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