question about preemption
Joel Sherrill <joel@OARcorp.com>
joel.sherrill at OARcorp.com
Thu Sep 16 12:49:48 UTC 2004
Eugeny S. Mints wrote:
> Hi Manuel,
>
> Manuel Pedro Coutinho wrote:
>
>> Hi
>>
>> I would like to know if a task which is in a system call (like an
>> device driver call) can be preempted
>> in the RTEMS
>
>
> RTMES in not Linux:)) First of all there are no "kernel"
> and "user" mode in RTEMS. Thus there is no such concept as
> "system call" similar to Linux. RTEMS uses preempting scheduling based
> on priorites
> what means that if a task gets ready and it's priority is higher than
> priority of currently running task, current
> task is preempted (the only exception is if preemption is explicitly
> disabled).
Nice description. It is permissible and commonly required for
drivers to temporarily disable preemption or interrupts to
perform some task atomically. The rule of thumb is keep the
disable period as short as possible and always restore things
to their prior state.
> Eugeny
>
>> thanks
>>
>> _________________________________________________________________
>> MSN Hotmail, o maior webmail do Brasil. http://www.hotmail.com
>>
>>
>>
>
>
\
--
Joel Sherrill, Ph.D. Director of Research & Development
joel at OARcorp.com On-Line Applications Research
Ask me about RTEMS: a free RTOS Huntsville AL 35805
Support Available (256) 722-9985
More information about the users
mailing list