vault backup: 2025-03-08 17:46:57

.obsidian/workspace.json

@@ -196,6 +196,7 @@
   "active": "802d9ec58484849d",
   "lastOpenFiles": [
     "Concurrent Systems/notes/Lezione2.md",
+    "Concurrent Systems/notes/1 - CS Basics.md",
     "HCIW/slides/Interface and Interaction for IoT.pdf",
     "Pasted image 20250305182542.png",
     "HCIW/notes/3 - Beacons.md",
@@ -215,7 +216,6 @@
     "Concurrent Systems/notes/images/Pasted image 20250304090207.png",
     "Concurrent Systems/notes/images/Pasted image 20250304084901.png",
     "Concurrent Systems/notes/images/Pasted image 20250304084537.png",
-    "Concurrent Systems/notes/1 - CS Basics.md",
     "Concurrent Systems/slides/class 1.pdf",
     "Data and Network Security/slides/2025 - DNS - Lecture 2.pdf",
     "Concurrent Systems/notes/images/Pasted image 20250303093116.png",

Concurrent Systems/notes/1 - CS Basics.md

@@ -92,20 +92,17 @@ Every solution to a problem should satisfy at least:
 >[!warning] So safety is necessary for correctness, liveness for meaningfulness.
 
 ##### In the context of MUTEX:
-- **Safety:** there is at most one process at a time in a CS.
+- **Safety:** there is at most one process at a time in a CS (*mutual exclusion*).
 - **Liveness:**
-	- **Deadlock freedom:** if there is at least one invocation of lock, eventually after at least one process enters a C.S.
-	- **Starvation freedom:** every invocation of lock eventually grants access to the associated C.S.
-	- **Bounded bypass:** let $n$ be the number of processes; then, there exists $f: N \to N$ s.t. every lock enters the C.S. after at most $f(n)$ other C.S.s (The process must win in at most f(n) steps).
+	- **Deadlock freedom:** if there is at least one invocation of `lock`, one process will eventually enter the critical section. This means that **the system is not blocked forever**.
+	- **Starvation freedom:** every invocation of lock eventually grants access to the associated CS (a process won't be stuck forever while other processes are racing for the CS).
+	- **Bounded bypass:** like starvation freedom, but stronger! We define an upper bound on the number of failures. Let $n$ be the number of processes; then, there exists $f: N \to N$ s.t. every lock enters the C.S. after at most $f(n)$ other CSs (The process must enter the CS in at most $f(n)$ steps).
 
-todo: riscrivere meglio l'ultimo
-
-
-Both inclusions are strict:
-Deadlock freedom $\not{\implies}$ Starvation freedom
+**Both inclusions are strict:**
+$$\text{Deadlock freedom} \not \implies \text{Starvation freedom}$$
 	![[Pasted image 20250303093116.png]]
 
-Starvation freedom $not \implies$ Bounded bypass
+Starvation freedom $\not \implies$ Bounded bypass
 	Assume a $f$ and consider the scheduling above, where p2 wins $f(3)$ times and so does p3, then p1 looses (at least) $2f(3)$ times before winning.
 
 ### Atomic R/W registers