linux-kernel - Re: [PATCH 01/12] arm64: hibernate.c: create a new function to handle cpu_up(sleep

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Date:   Tue, 19 Nov 2019 23:21:31 +0000
From:   Qais Yousef <qais.yousef@....com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Steve Capper <steve.capper@....com>,
        Richard Fontana <rfontana@...hat.com>,
        James Morse <james.morse@....com>,
        Mark Rutland <mark.rutland@....com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Ingo Molnar <mingo@...nel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Jiri Kosina <jkosina@...e.cz>,
        Pavankumar Kondeti <pkondeti@...eaurora.org>,
        Zhenzhong Duan <zhenzhong.duan@...cle.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/12] arm64: hibernate.c: create a new function to
 handle cpu_up(sleep_cpu)

On 11/20/19 00:01, Thomas Gleixner wrote:
> On Tue, 19 Nov 2019, Qais Yousef wrote:
> > On 11/19/19 23:31, Thomas Gleixner wrote:
> > > On Wed, 30 Oct 2019, Qais Yousef wrote:
> > > >  
> > > > +int hibernation_bringup_sleep_cpu(unsigned int sleep_cpu)
> > > 
> > > That function name is horrible. Aside of that I really have to ask how you
> > > end up hibernating on an offline CPU?
> > 
> > James Morse can probably explain better.
> > 
> > But AFAIU we could sleep on any CPU, but on the next cold boot that CPU could
> > become offline as a side effect of using maxcpus= for example.
> > 
> > How about bringup_hibernate_cpu() as a name? I could add the above as an
> > explanation of why we need this call too.
> > 
> > It does seem to me that this is a generic problem that we might be able to
> > handle generically, but I'm not sure how.
> 
> Don't know about other architectures, but x86 does not have that issue as
> we force hibernation on CPU0 for historical reasons (Broken BIOSes etc.).

I'll avoid making this series bigger then.

Thanks

--
Qais Yousef