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From: David Miller <davem@davemloft.net>
To: vijay.ac.kumar@oracle.com
Cc: sparclinux@vger.kernel.org, rob.gardner@oracle.com,
	anthony.yznaga@oracle.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/2] sparc64: Use low latency path to resume idle cpu
Date: Fri, 21 Jul 2017 03:55:26 +0100 (WEST)	[thread overview]
Message-ID: <20170721.035526.1236051430538663900.davem@davemloft.net> (raw)
In-Reply-To: <dbe44a81-e5fd-3baf-084e-475db05ba397@oracle.com>

From: Vijay Kumar <vijay.ac.kumar@oracle.com>
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 :)

  reply	other threads:[~2017-07-21  2:55 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-07-08 20:23 [PATCH 0/2] sparc64: Use low latency path to resume idle cpu Vijay Kumar
2017-07-08 20:23 ` [PATCH 1/2] sparc64: Add a new hypercall CPU_POKE Vijay Kumar
2017-07-08 20:23 ` [PATCH 2/2] sparc64: Use cpu_poke to resume idle cpu Vijay Kumar
2017-07-20 19:58   ` David Miller
2017-07-21  2:47     ` Vijay Kumar
2017-07-20 19:57 ` [PATCH 0/2] sparc64: Use low latency path " David Miller
2017-07-21  2:44   ` Vijay Kumar
2017-07-21  2:55     ` David Miller [this message]
2017-07-21  3:36       ` Vijay Kumar
2017-07-21  3:45         ` David Miller
2017-07-21  4:11           ` Vijay Kumar

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