linux-kernel - Re: [guv v2 23/31] tile: Replace __get_cpu

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Date:	Wed, 28 Aug 2013 17:54:24 +0000
From:	Christoph Lameter <cl@...ux.com>
To:	Chris Metcalf <cmetcalf@...era.com>
cc:	Tejun Heo <tj@...nel.org>, akpm@...uxfoundation.org,
	linux-arch@...r.kernel.org, Steven Rostedt <srostedt@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [guv v2 23/31] tile: Replace __get_cpu_var uses

On Wed, 28 Aug 2013, Chris Metcalf wrote:

> Taken into the tile tree, with one extra change; in
> arch/tile/kernel/messaging.c, using "__this_cpu_read(msg_state)"
> generated warnings ("'pscr_ret__.opaque[1u]' is used uninitialized in
> this function", etc), since msg_state is a struct, so I changed it to be
> "*__this_cpu_ptr(&msg_state)".  Interrupts are disabled here so
> preemption is not a concern.

Well yes. __this_cpu_read can only be used to read scalars. If you want to
transfer a struct then memcpy needs to be used (or the compiler can do
that for you like above).

> In addition, I applied the following commit to clean up the remaining
> uses that are currently only being carried in the linux-tile tree.

You are going to merge these changes right? I can drop the tile patch from
my series?


One small issue below:

> diff --git a/arch/tile/kernel/time.c b/arch/tile/kernel/time.c
> index a7a41a1..30c2c34 100644
> --- a/arch/tile/kernel/time.c
> +++ b/arch/tile/kernel/time.c
> @@ -286,7 +286,7 @@ static int _set_clock_rate_barrier;
>  static int _set_clock_rate(void *arg)
>  {
>         struct _set_clock_rate_args *args = arg;
> -       struct clock_event_device *evt = &__get_cpu_var(tile_timer);
> +       struct clock_event_device *evt = get_cpu_ptr(&tile_timer);
					^^^^ this_cpu_ptr


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