Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!samsung!uunet!bywater!arnor!news
From: oleg@ibm.com
Newsgroups: comp.os.os2.programmer
Subject: Re: Preemptive multitasking
Message-ID: <1990Dec14.165116.22948@arnor.uucp>
Date: 14 Dec 90 16:51:16 GMT
Sender: news@arnor.uucp (NNTP News Poster)
Organization: IBM T.J. Watson Research Center
Lines: 15


> Each time the timer fires, the scheduler will decide whether it needs to
> switch the CPU to some other thread than the one executing when the timer
> went off.  If some new thread is ready to run, and has a higher priority
> than the currently running thread, then the scheduler will immediately set
> the CPU to switch to that thread, pausing the currently running thread.

According to an article "Measure Your Machine's Activity ..." in November 90
issue of Microsoft System Journal, the scheduler can cut right into the middle
of a thread's time slice and steal the CPU away. This happens if a thread
makes a system call, and there is another thread with a higher priority ready
to be dispatched.

Oleg Vishnepolsky
IBM T. J. Watson Research Center