linux-kernel - Re: [RFC PATCH v2 3/7] sched/idle: Add poll before enter real idle path

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Message-ID: <20170829124545.bonzgnoewlrphalm@hirez.programming.kicks-ass.net>
Date:   Tue, 29 Aug 2017 14:45:45 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Yang Zhang <yang.zhang.wz@...il.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        wanpeng.li@...mail.com, mst@...hat.com, pbonzini@...hat.com,
        tglx@...utronix.de, rkrcmar@...hat.com, dmatlack@...gle.com,
        agraf@...e.de, linux-doc@...r.kernel.org,
        Quan Xu <quan.xu0@...il.com>, Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Borislav Petkov <bp@...en8.de>, Kyle Huey <me@...ehuey.com>,
        Andy Lutomirski <luto@...nel.org>,
        Len Brown <len.brown@...el.com>
Subject: Re: [RFC PATCH v2 3/7] sched/idle: Add poll before enter real idle
 path

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@...il.com>
> Signed-off-by: Quan Xu <quan.xu0@...il.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?