Date: Tue, 29 Aug 2017 14:45:45 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Yang Zhang <yang.zhang.wz@gmail.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        wanpeng.li@hotmail.com, mst@redhat.com, pbonzini@redhat.com,
        tglx@linutronix.de, rkrcmar@redhat.com, dmatlack@google.com,
        agraf@suse.de, linux-doc@vger.kernel.org, Quan Xu <quan.xu0@gmail.com>,
        Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
        x86@kernel.org, Borislav Petkov <bp@alien8.de>,
        Kyle Huey <me@kylehuey.com>, Andy Lutomirski <luto@kernel.org>,
        Len Brown <len.brown@intel.com>
Subject: Re: [RFC PATCH v2 3/7] sched/idle: Add poll before enter real idle
 path
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On Tue, Aug 29, 2017 at 11:46:37AM +0000, Yang Zhang wrote:
> Add poll in do_idle. For UP VM, if there are running task, it will not
> goes into idle path, so we only enable poll in SMP VM.
> 
> Signed-off-by: Yang Zhang <yang.zhang.wz@gmail.com>
> Signed-off-by: Quan Xu <quan.xu0@gmail.com>

Broken SoB chain.

> diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
> index 6c23e30..b374744 100644
> --- a/kernel/sched/idle.c
> +++ b/kernel/sched/idle.c
> @@ -74,6 +74,7 @@ static noinline int __cpuidle cpu_idle_poll(void)
>  }
>  
>  /* Weak implementations for optional arch specific functions */
> +void __weak arch_cpu_idle_poll(void) { }
>  void __weak arch_cpu_idle_prepare(void) { }
>  void __weak arch_cpu_idle_enter(void) { }

And not a word on why we need a new arch hook. What's wrong with
arch_cpu_idle_enter() for instance?