From 6bd7ddb752a1f49958aeda82acd821a447e301cf Mon Sep 17 00:00:00 2001
From: Marco Realacci <marco@marcorealacci.me>
Date: Wed, 12 Mar 2025 11:09:27 +0100
Subject: [PATCH] vault backup: 2025-03-12 11:09:27

---
 Concurrent Systems/notes/4 - Semaphores.md | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/Concurrent Systems/notes/4 - Semaphores.md b/Concurrent Systems/notes/4 - Semaphores.md
index d5c6c07..f1a1ebf 100644
--- a/Concurrent Systems/notes/4 - Semaphores.md	
+++ b/Concurrent Systems/notes/4 - Semaphores.md	
@@ -101,7 +101,7 @@ B.consume() :=
 B.produce(v) :=
 	FREE.down()
 	SP.down()
-	while not EMPTY[in] do
+	while not EMPTY[in] do # there is at least an EMPTY cell, otherwise it would have been blocked
 		IN <- (IN+1) mod k
 	i <- IN
 	EMPTY[IN] <- ff
@@ -111,5 +111,16 @@ B.produce(v) :=
 	BUSY.up()
 	return
 
-
+B.consume() :=
+	BUSY.down()
+	SC.down()
+	while not FULL[OUT] do
+		OUT <- (OUT+1) mod k
+	o <- OUT
+	FULL[OUT] <- ff
+	SC.up()
+	tmp <- BUF[o]
+	EMPTY[o] <- tt
+	FREE.up()
+	return tmp		
 ```
\ No newline at end of file