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Subject: Re: [git pull] scheduler/misc fixes
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: David Miller <davem@davemloft.net>
Cc: mingo@elte.hu, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org,
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       alan@lxorguk.ukuu.org.uk, tglx@linutronix.de
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Date: Fri, 25 Apr 2008 10:24:18 +0200
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On Fri, 2008-04-25 at 00:57 -0700, David Miller wrote:

> diff --git a/arch/sparc64/kernel/smp.c b/arch/sparc64/kernel/smp.c
> index 524b889..bf4ef84 100644
> --- a/arch/sparc64/kernel/smp.c
> +++ b/arch/sparc64/kernel/smp.c
> @@ -866,14 +866,21 @@ void smp_call_function_client(int irq, struct pt_regs *regs)
>  	void *info = call_data->info;
>  
>  	clear_softint(1 << irq);
> +
> +	irq_enter();
> +
> +	if (!call_data->wait) {
> +		/* let initiator proceed after getting data */
> +		atomic_inc(&call_data->finished);
> +	}
> +
> +	func(info);
> +
> +	irq_exit();
> +
>  	if (call_data->wait) {
>  		/* let initiator proceed only after completion */
> -		func(info);
> -		atomic_inc(&call_data->finished);
> -	} else {
> -		/* let initiator proceed after getting data */
>  		atomic_inc(&call_data->finished);
> -		func(info);
>  	}
>  }


FWIW I do think this is a valid 'bug' fix in that the called user func()
can now see its from interrupt context. in_interrupt() would have
reported false due to the missing irq_enter()/irq_exit() - not sure if
any smp_call_function() relies on it though.