vault backup: 2025-04-03 18:21:35

Concurrent Systems/test/Untitled.md

@@ -34,3 +34,37 @@ end_write() :=
 	GLOB_MUTEX.up()
 	return
 ```
+
+```
+monitor RW_READERS :=
+	AR, WR, AW, WW, LASTW init at 0
+	condition CR, CW
+
+operation begin_read() :=
+	if WW + AW != 0 then
+		CR.wait()
+		CR.signal()
+	AR++
+
+operation end_read() :=
+	AR--
+	if AR = 0 then
+		CW.signal()
+
+operation begin_write() :=
+	WW++
+	LASTW <- i
+	CW.signal() # wakes eventually other waiting writers *they will return false*
+	if (AR + AW != 0) then
+		CW.wait()
+	if LASTW
+	AW++
+	WW--
+
+operation end_write() :=
+	AW--
+	if WW > 0 then
+		CW.signal()
+	else
+		CR.signal()
+```