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Date: Sat, 25 Feb 2006 20:04:01 +0900
From: Kazuaki Oda <kaakun@highway.ne.jp>
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Subject: question about preemption code
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Hi,

When reading kern_switch.c, I noticed odd difference between !SMP and
SMP in maybe_preempt_in_ksegrp().

In !SMP case:
=================================================================
#ifdef PREEMPTION
#ifndef FULL_PREEMPTION
	if (td->td_priority > PRI_MAX_ITHD) {
		running_thread->td_flags |= TDF_NEEDRESCHED;
		return;
	}
#endif /* FULL_PREEMPTION */
=================================================================

In SMP case:
=================================================================
#ifdef PREEMPTION

#if !defined(FULL_PREEMPTION)
	if (td->td_priority > PRI_MAX_ITHD) {
		running_thread->td_flags |= TDF_NEEDRESCHED;
	}
#endif /* ! FULL_PREEMPTION */
=================================================================

Is there any reason not to return after setting TDF_NEEDRESCHED flag
in SMP case?  Because of this, we do context switch even if td's
priority is lower than PRI_MAX_ITHD.  And, I think, it is not
PREEMPTION, but FULL_PREEMPTION.

----
Kazuaki Oda