Date: Thu, 7 May 2015 11:58:32 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Mike Galbraith <umgwanakikbuti@gmail.com>,
        Chris Metcalf <cmetcalf@ezchip.com>, Dave Jones <davej@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>, Oleg Nesterov <oleg@redhat.com>,
        "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
        Ingo Molnar <mingo@redhat.com>, Rik van Riel <riel@redhat.com>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>
Subject: Re: [PATCH 1/4] context_tracking: Protect against recursion
Message-ID: <20150507095832.GA7976@gmail.com>
References: <1430928266-24888-1-git-send-email-fweisbec@gmail.com>
 <1430928266-24888-2-git-send-email-fweisbec@gmail.com>
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* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> @@ -75,6 +94,11 @@ void context_tracking_enter(enum ctx_state state)
>  	WARN_ON_ONCE(!current->mm);
>  
>  	local_irq_save(flags);
> +	if (!context_tracking_recursion_enter()) {
> +		local_irq_restore(flags);
> +		return;
> +	}
> +
>  	if ( __this_cpu_read(context_tracking.state) != state) {
>  		if (__this_cpu_read(context_tracking.active)) {
>  			/*
> @@ -105,6 +129,7 @@ void context_tracking_enter(enum ctx_state state)
>  		 */
>  		__this_cpu_write(context_tracking.state, state);
>  	}
> +	context_tracking_recursion_exit();

>  	local_irq_restore(flags);
>  }

So why not add an 'out_irq_restore:' label and use goto instead of 
duplicating the return path in the recursion check?

>  NOKPROBE_SYMBOL(context_tracking_enter);
> @@ -139,6 +164,10 @@ void context_tracking_exit(enum ctx_state state)
>  		return;
>  
>  	local_irq_save(flags);
> +	if (!context_tracking_recursion_enter()) {
> +		local_irq_restore(flags);
> +		return;

Ditto.

No need to resend, I fixed this up in the patch.

Thanks,

	Ingo
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