linux-kernel - Re: [patch 00/12] (hr)timers: Prepare for PREEMPT

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Message-ID: <20190729194550.GP31398@hirez.programming.kicks-ass.net>
Date:   Mon, 29 Jul 2019 21:45:50 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Steven Rostedt <rostedt@...dmis.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>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Juergen Gross <jgross@...e.com>
Subject: Re: [patch 00/12] (hr)timers: Prepare for PREEMPT_RT support

On Fri, Jul 26, 2019 at 08:30:48PM +0200, Thomas Gleixner wrote:
> The following series brings the bulk of PREEMPT_RT specific changes for the
> (hr)timer code:
> 
>   - Handle timer deletion correctly under RT to avoid priority inversion
>     and life locks
> 
>     This mechanism might be useful for VMs as well when a vCPU
>     executing a timer callback gets scheduled out and on another vCPU
>     del_timer_sync() or hrtimer_cancel() is invoked.
> 
>     The mitigation would only work when paravirt spinlocks are
>     enabled. I've not implemented that, as I don't know whether this is a
>     real world issue. I just noticed that it is basically the same
>     problem. Adding it would be trivial.
> 
>   - Prepare for moving most hrtimer callbacks into softirq context and mark
>     timers which need to expire in hard interrupt context even on RT so
>     they don't get moved.
> 

Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>