User-level threads ( ULt thread management done by a threads library at user mode/space thread spawning, destruction, scheduling, message passing switching--saving and restoring thread context setting state of each thread kernel not aware of existence of threads ° Examples in Fig.4,7 Fig 4.7b: thread 2 invokes 1/O action Fig 4.7c: process Bs clock quantum expires Fig. 4.7d thread 2 needs some action performed by thread I thread switching occurs and is managed by threads library 1515 User-level threads (ULT) • thread management done by a threads library at user mode/space – thread spawning, destruction, scheduling, message passing, switching--saving and restoring thread context – setting state of each thread • kernel not aware of existence of threads • Examples in Fig. 4.7 – Fig. 4.7b: thread 2 invokes I/O action. – Fig. 4.7c: process B’s clock quantum expires. – Fig. 4.7d: thread 2 needs some action performed by thread 1; thread switching occurs and is managed by threads library