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Date:   Thu, 1 Aug 2019 17:10:54 +0200 (CEST)
From:   Thomas Gleixner <tglx@linutronix.de>
To:     Peter Zijlstra <peterz@infradead.org>
cc:     LKML <linux-kernel@vger.kernel.org>, x86@kernel.org,
        Ingo Molnar <mingo@kernel.org>,
        Sebastian Siewior <bigeasy@linutronix.de>,
        Anna-Maria Gleixner <anna-maria@linutronix.de>,
        Steven Rostedt <rostedt@goodmis.org>,
        Julia Cartwright <julia@ni.com>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        John Stultz <john.stultz@linaro.org>,
        Andy Lutomirski <luto@kernel.org>,
        "Paul E. McKenney" <paulmck@linux.ibm.com>,
        Oleg Nesterov <oleg@redhat.com>, kvm@vger.kernel.org,
        Radim Krcmar <rkrcmar@redhat.com>,
        Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [patch 4/5] posix-cpu-timers: Defer timer handling to
 task_work
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References: <20190801143250.370326052@linutronix.de> <20190801143658.074833024@linutronix.de> <20190801145116.GD31398@hirez.programming.kicks-ass.net>
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On Thu, 1 Aug 2019, Peter Zijlstra wrote:
> On Thu, Aug 01, 2019 at 04:32:54PM +0200, Thomas Gleixner wrote:
> > --- a/kernel/time/Kconfig
> > +++ b/kernel/time/Kconfig
> > @@ -52,6 +52,11 @@ config GENERIC_CLOCKEVENTS_MIN_ADJUST
> >  config GENERIC_CMOS_UPDATE
> >  	bool
> >  
> > +# Select to handle posix CPU timers from task_work
> > +# and not from the timer interrupt context
> > +config POSIX_CPU_TIMERS_TASK_WORK
> > +	bool
> > +
> >  if GENERIC_CLOCKEVENTS
> >  menu "Timers subsystem"
> >  
> 
> 
> diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt
> index deff97217496..76e37ad5bc31 100644
> --- a/kernel/Kconfig.preempt
> +++ b/kernel/Kconfig.preempt
> @@ -58,6 +58,7 @@ config PREEMPT
>  config PREEMPT_RT
>  	bool "Fully Preemptible Kernel (Real-Time)"
>  	depends on EXPERT && ARCH_SUPPORTS_RT
> +	depends on POSIX_CPU_TIMERS_TASK_WORK

Indeed.