Re: [Linux-ia64] Help with Ingo scheduler on IA64

David Mosberger
2002-01-21T20:23:08Z

>>>>> On Mon, 21 Jan 2002 23:11:49 +0100 (CET), Ingo Molnar <mingo@elte.hu> said:

Ingo> On Mon, 21 Jan 2002, David Mosberger wrote:

Ingo> we call context_switch() with irqs disabled. The ia64 version
Ingo> of switch_to() should not re-enable IRQs or it will deadlock.
>> The existing switch_to() enables interrupts if the new task's
>> stack is on a different (kernel-) page.

Ingo> oh, i see. Why were irqs enabled explicitly? The old scheduler
Ingo> called switch_to() with irqs enabled, all the time.

Eh, that's not true. The old scheduler did spin_unlock_irq() before
calling switch_to(). If your scheduler requires irq's to be disabled
during context switch, it's going to have bigger interrupt response
latency. That's a disadvantage.

--david