Systemsoftware

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Beispiel: Weckdienst (2) MONITOR Clock int now; /*Absolutzeit*/ Condition Wakeup; ENTRY WakeMe (int N) { /*N=relative Weckzeit*/ int next; next=now+N; while (now
Beispiel: Plattenkopfsteuerung (2) MONITOR DiscHead int HeadPos; /*0..Cylmax*/ enum {Up,Down} Direction; enum {nein,ja} Busy; Condition UpSweep,DownSweep; ENTRY Request(int Dest) { if (busy==ja) { if (Direction==Up) { if (HeadPos=Dest) DownSweep.Wait(Cylmax-Dest); else UpSweep.Wait(Dest); } } Busy=ja; HeadPos=Dest; } <strong>Systemsoftware</strong> - Lektion X 25 Beispiel: Plattenkopfsteuerung (3) ENTRY Release() { Busy=nein; if (Direction==Up) { if (UpSweep.Status()!=0) UpSweep.Signal(); else { Direction=Down; DownSweep.Signal(); } else {/*Direction==Down*/ if (DownSweep.Status()!=0) DownSweep.Signal(); else { Direction=Up; UpSweep.Signal(); } } INIT { HeadPos=0; Direction=Up; Busy=nein; } END Release <strong>Systemsoftware</strong> - Lektion X 26
Page 1 and 2: Systemsoftware Jürgen Nehmer, WS 2
Page 3 and 4: Veranschaulichung von Signal und Wa
Page 5 and 6: Beispiel 1: Monitor = exklusive Res
Page 7 and 8: Beispiel 5:Reader-Writer-Problem (W
Page 9 and 10: Implementierung von Condition-Varia
Page 11: Vorgeschlagene Erweiterungen des Mo

Systemsoftware

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