Re-entrant Operating Systems (was: *nix performance)

[Keith Gabryelski]

Distribution has been limited to comp.unix.questions and
comp.sys.ibm.pc.

Follow ups to comp.sys.ibm.pc.

In article <1279 at umbc3.UMD.EDU> brian at umbc3.UMD.EDU (Brian Cuthie) writes:
>In article <168 at ernie.NECAM.COM> koll at ernie.NECAM.COM (Michael Goldman)
 writes:
>>There are some other problems
>>with DMA on the PC. One is that DOS is not re-entrant and so you have
>>to VERRRY Carefully save the state with any program that uses interrupts
>>which is implicit in any reasonable application with DMA.  With all the
>
>Besides, I know what re-entrant instructions are (and besides,
>they're "restartable instructions", but that's a different point),
>but what the !%^%@ is a re-entrant operating system.

For DOS people, re-entrant operating system, does indeed, mean
something.  DOS was written without any regards for multi-tasking
programs.

In DOS, the system routines use the same static buffers.  This
prevents two routines, say a foreground process and a TSR, from doing
DOS calls at the same time.  There is infact a flag that is set when a
DOS call is initiated that should be checked by all TSRs before
attempting any DOS call.

So, in the contex in which Micahael was talking, the answer to your
question...

>Can you name one ?? I bet not.

... is Unix.

Pax, Keith
-- 
ag at elgar.CTS.COM         Keith Gabryelski          ...!{ucsd, jack}!elgar!ag