Hi...
I have a couple of questions regarding cond_resched().
The first one is: what's the motivation to introduce this function?
IMHO, it prevents user from incorrectly calling schedule() in atomic or
can-not-be-preempted situation. Also, by checking for need_resched(), it
only schedules if the current task is really told to be kicked out. This
will save TLB flush in certain condition i.e switching between full
processes, not threads
The second question is, why the cond_resched() have PREEMPT_ACTIVE
flag set before calling schedule()? The comments seems to say it is to
prevent a second (recursive?) call of cond_resched(), but I can not
see any recursive call in the source code. Did I miss anything?
Well, since it is a preventive act and likely everybody knows that
he/she should avoid recursive cond_resched() invocation, then you see
none. But of course, someday somebody could make mistake related to this
issue, this is where the safeguard kicks in :)
regards,
Mulyadi
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