linux-kernel - Re: [patch] generic-ipi: remove kmalloc, cleanup

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Date:	Thu, 12 Feb 2009 13:36:11 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...x.de>,
	LKML <linux-kernel@...r.kernel.org>,
	rt-users <linux-rt-users@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Carsten Emde <ce@...g.ch>,
	Clark Williams <williams@...hat.com>,
	rusty <rusty@...tcorp.com.au>
Subject: Re: [patch] generic-ipi: remove kmalloc, cleanup

On Thu, 2009-02-12 at 13:09 +0100, Peter Zijlstra wrote:


> @@ -137,8 +137,10 @@ void generic_smp_call_function_interrupt(void)
>  			 */
>  			smp_wmb();
>  			data->csd.flags &= ~CSD_FLAG_WAIT;
> -		}
> -		if (data->csd.flags & CSD_FLAG_ALLOC)
> +		} else if (data->csd.flags & CSD_FLAG_LOCK) {
> +			smp_wmb();
> +			data->csd.flags &= ~CSD_FLAG_LOCK;
> +		} else if (data->csd.flags & CSD_FLAG_ALLOC)
>  			call_rcu(&data->rcu_head, rcu_free_call_data);
>  	}
>  	rcu_read_unlock();

Hmm, I think this bit ought to go in rcu_free_call_data(), otherwise we
can have that same race again..

I'd better put a comment in on why we use RCU here.
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