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SubjectRe: (no subject)
On Mon, 23 Oct 2000, Marco wrote:

> Hi,
> can someone briefly explain me how the kernel code prevent the
> preemption of process executing a system call ? I read several technical
> papers but I haven't found (or perhaps don't understood) a response
> there.
> Many thanks in advance
>
> Marco Bacchetta
>

A system call does not cause a preemption. In Unix/Linux, the system
call executes in the context of the user. The only time preemption
occurs, as a result of a system call, is when waiting for I/O to complete
or some similar resource. In this case, instead of spinning, wasting
CPU cycles, the kernel gives the CPU to somebody else who could use
it while your I/O is completing.


Cheers,
Dick Johnson

Penguin : Linux version 2.2.17 on an i686 machine (801.18 BogoMips).

"Memory is like gasoline. You use it up when you are running. Of
course you get it all back when you reboot..."; Actual explanation
obtained from the Micro$oft help desk.


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