Date: Tue, 7 Apr 2015 21:17:18 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Jason Low <jason.low2@hp.com>
cc: Peter Zijlstra <peterz@infradead.org>,
        Mike Galbraith <umgwanakikbuti@gmail.com>,
        Thavatchai Makphaibulchoke <tmac@hp.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@redhat.com>,
        linux-rt-users <linux-rt-users@vger.kernel.org>
Subject: Re: [PATCH v2 1/2] rtmutex Real-Time Linux: Fixing kernel BUG at
 kernel/locking/rtmutex.c:997!
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On Tue, 7 Apr 2015, Jason Low wrote:
> The lock shouldn't be used in get_next_timer_interrupt() either right?
> 
> unsigned long get_next_timer_interrupt(unsigned long now)
> {
> ...
> 
> #ifdef CONFIG_PREEMPT_RT_FULL
>         /*
>          * On PREEMPT_RT we cannot sleep here. If the trylock does not
>          * succeed then we return the worst-case 'expires in 1 tick'
>          * value.  We use the rt functions here directly to avoid a
>          * migrate_disable() call.
>          */
>         if (!spin_do_trylock(&base->lock))
>                 return  now + 1;
> #else

And how do you protect the walk of the timer wheel against a
concurrent insertion/removal?

Thanks,

	tglx

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