linux-kernel - Re: [patch 11/12] hrtimer: Prepare support for PREEMPT

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Message-ID: <9a9bde89-e0b3-a7b9-749e-a6b35d74b729@redhat.com>
Date:   Mon, 29 Jul 2019 19:30:33 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Juergen Gross <jgross@...e.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Sebastian Siewior <bigeasy@...utronix.de>,
        Anna-Maria Gleixner <anna-maria@...utronix.de>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>
Subject: Re: [patch 11/12] hrtimer: Prepare support for PREEMPT_RT

On 29/07/19 17:08, Steven Rostedt wrote:
> On Sun, 28 Jul 2019 11:06:50 +0200
> Juergen Gross <jgross@...e.com> wrote:
> 
>> In case we'd want to change that I'd rather not special case timers, but
>> apply a more general solution to the quite large amount of similar
>> cases: I assume the majority of cpu_relax() uses are affected, so adding
>> a paravirt op cpu_relax() might be appropriate.
>>
>> That could be put under CONFIG_PARAVIRT_SPINLOCK. If called in a guest
>> it could ask the hypervisor to give up the physical cpu voluntarily
>> (in Xen this would be a "yield" hypercall).
> 
> Seems paravirt wants our cpu_chill() ;-)

Actually that is not really a joke! :)

Paolo