Re: [PATCH 0/2] sparc64: Use low latency path to resume idle cpu

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On 7/20/2017 9:55 PM, David Miller wrote:
From: Vijay Kumar <vijay.ac.kumar@xxxxxxxxxx>
Date: Thu, 20 Jul 2017 21:44:24 -0500

I had same thoughts initially but I had to go with this approach as
scheduler_ipi is wrapped with irq_enter() and irq_exit(). Whereas POKE
resumes the cpu in process context.

Comments in scheduler_ipi():

          * Not all reschedule IPI handlers call irq_enter/irq_exit, since
          * traditionally all their work was done from the interrupt return
          * path. Now that we actually do some work, we need to make sure
          * we do call them.
          *
          * Some archs already do call them, luckily irq_enter/exit nest
          * properly.
          *
          * Arguably we should visit all archs and update all handlers,
          * however a fair share of IPIs are still resched only so this would
          * somewhat pessimize the simple resched case.
          */
         irq_enter();

I still think we should be able to fake the state such that this
direct schedule_ipi() call will work.

I could be wrong :)
I can give a try :). But looks to me one thing that will go wrong is irq accounting done in __irq_enter() and rcu_irq_enter().

Thanks,
Vijay

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