From cccc568cc57e0ba60044fcae26275f757fdf5e64 Mon Sep 17 00:00:00 2001
From: Marco Realacci <marco@marcorealacci.me>
Date: Mon, 17 Mar 2025 09:39:23 +0100
Subject: [PATCH] vault backup: 2025-03-17 09:39:23

---
 .obsidian/workspace.json         |  4 ++--
 Concurrent Systems/notes/4b -.md | 23 +++++++++++++++++++++--
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/.obsidian/workspace.json b/.obsidian/workspace.json
index e6a430b..47d531b 100644
--- a/.obsidian/workspace.json
+++ b/.obsidian/workspace.json
@@ -216,10 +216,10 @@
       "companion:Toggle completion": false
     }
   },
-  "active": "071b6cd23e4b1e9d",
+  "active": "6edd4157a160e462",
   "lastOpenFiles": [
-    "Concurrent Systems/notes/4b -.md",
     "Concurrent Systems/slides/class 4.pdf",
+    "Concurrent Systems/notes/4b -.md",
     "Concurrent Systems/slides/class 5.pdf",
     "HCIW/slides/4 HUI2016-6-forcefeedback.pdf",
     "HCIW/slides/3b Haptic slides.pdf",
diff --git a/Concurrent Systems/notes/4b -.md b/Concurrent Systems/notes/4b -.md
index 6c99f96..2f5ff51 100644
--- a/Concurrent Systems/notes/4b -.md	
+++ b/Concurrent Systems/notes/4b -.md	
@@ -35,5 +35,24 @@ Of course, `signal()` will have no effect on the last process who calls it.
 - For every condition C, a semaphore SEMC init at 0 and an integer $N_{C}$ init at 0 (to store and count the number of suspended processes on the given condition)
 - A semaphore PRIO init at 0 and an integer $N_{PR}$ init at 0 (to store and count the number of processes that have performed a signal, and so have priority to re-enter the monitor)
 
-1. Every monitor operation starts with `MUTEX.down()` and ends with `if NPR > 0 then PRIO.up() else MUTEX.up()`
-2. 
\ No newline at end of file
+Every monitor operation starts with `MUTEX.down()` and ends with `if NPR > 0 then PRIO.up() else MUTEX.up()`
+
+```
+C.wait() :=
+	NC++
+	if NPR > 0 then
+		PRIO.up()
+	else
+		MUTEX.up()
+	SEMC.down()
+	NC--
+	return
+
+C.signal() :=
+	if NC > 0 then
+		NPR++
+		SEMC.up()
+		PRIO.down()
+		NPR--
+```
+