vault backup: 2025-03-12 12:19:27

.obsidian/workspace.json

@@ -34,9 +34,9 @@
               "type": "pdf",
               "state": {
                 "file": "Concurrent Systems/slides/class 4.pdf",
-                "page": 10,
+                "page": 6,
                 "left": -23,
-                "top": 122,
+                "top": 126,
                 "zoom": 0.652019002375297
               },
               "icon": "lucide-file-text",
@@ -217,6 +217,7 @@
   },
   "active": "6edd4157a160e462",
   "lastOpenFiles": [
+    "Concurrent Systems/notes/images/Pasted image 20250312121828.png",
     "Concurrent Systems/slides/class 4.pdf",
     "Concurrent Systems/notes/4 - Semaphores.md",
     "Concurrent Systems/notes/3a - Hardware primitives & Lamport Bakery algorithm.md",

Concurrent Systems/notes/4 - Semaphores.md

@@ -162,18 +162,26 @@ producer A:
 - ...
 - writes at BUF[n], so IN becomes 0
 
+**Now there are no free slots.**
+
 consumer A:
 - starts reading BUF[0], now OUT is 1
+	- it is a sloooooooooow consumer
 
 consumer B:
-- finds OUT at 1
+- finds OUT at 1, sets OUT at 2 and starts reading
-- sets OUT at 2 and starts reading
+- finishes reading (before consumer A)
-- finishes reading
 - sets EMPTY[1] <- tt
+- calls `FREE.up()`
 
-consumer A:
+producer A:
-- finishes reading (finally)
+- as consumer B called `FREE.up()`, the producer can finally produce
-- sets EMPTY[0] <- tt
+- remember, IN is set to 0!
+- so producer A will write at `BUF[0]`
+- but wait! Consumer B is still reading there
+- **Producer A doesn't give a fuck.**
+	![[Pasted image 20250312121828.png|200]]
+	*don't be like Producer A, be more like Bob*