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Date: Tue, 19 Nov 2013 00:59:59 +0100
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        Mike Galbraith <bitbucket@online.de>,
        LKML <linux-kernel@vger.kernel.org>,
        RT <linux-rt-users@vger.kernel.org>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH v2] rtmutex: take the waiter lock with irqs off
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On Mon, Nov 18, 2013 at 03:10:21PM +0100, Peter Zijlstra wrote:
> --- a/kernel/softirq.c
> +++ b/kernel/softirq.c
> @@ -746,13 +746,23 @@ void irq_exit(void)
>  #endif
>  
>  	account_irq_exit_time(current);
> -	trace_hardirq_exit();
>  	sub_preempt_count(HARDIRQ_OFFSET);
> -	if (!in_interrupt() && local_softirq_pending())
> +	if (!in_interrupt() && local_softirq_pending()) {
> +		/*
> +		 * Temp. disable hardirq context so as not to confuse lockdep;
> +		 * otherwise it might think we're running softirq handler from
> +		 * hardirq context.
> +		 *
> +		 * Should probably sort this someplace else..
> +		 */
> +		trace_hardirq_exit();
>  		invoke_softirq();
> +		trace_hardirq_enter();
> +	}
>  
>  	tick_irq_exit();
>  	rcu_irq_exit();
> +	trace_hardirq_exit();

Looks like a change we really want!

Thanks!

>  }
>  
>  void raise_softirq(unsigned int nr)