[PATCH] Fix atomicity of TIF update in flush_thread() for powerpc

[Benjamin Herrenschmidt]

 .../...

> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at polymtl.ca>

Acked-by: Benjamin Herrenschmidt <benh at 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();