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Subject: Re: [PATCH] Fix atomicity of TIF update in flush_thread() for powerpc
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
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References: <20070309024525.GB9462@Krystal>
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Date: Fri, 09 Mar 2007 14:06:39 +0100
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> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>

Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Nice catch !

> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -476,8 +476,13 @@ void flush_thread(void)
>  #ifdef CONFIG_PPC64
>  	struct thread_info *t = current_thread_info();
>  
> -	if (t->flags & _TIF_ABI_PENDING)
> -		t->flags ^= (_TIF_ABI_PENDING | _TIF_32BIT);
> +	if (test_tsk_thread_flag(tsk, TIF_ABI_PENDING)) {
> +		clear_tsk_thread_flag(tsk, TIF_ABI_PENDING);
> +		if (test_tsk_thread_flag(tsk, TIF_32BIT))
> +			clear_tsk_thread_flag(tsk, TIF_32BIT);
> +		else
> +			set_tsk_thread_flag(tsk, TIF_32BIT);
> +	}
>  #endif
>  
>  	discard_lazy_cpu_state();