Re: [RFC/PATCH] Make powerpc64 use __thread for per-cpu variables

From: Richard Henderson <rth@twiddle.net>
To: Paul Mackerras <paulus@samba.org>
Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	linuxppc-dev@ozlabs.org
Subject: Re: [RFC/PATCH] Make powerpc64 use __thread for per-cpu variables
Date: Wed, 10 May 2006 08:47:13 -0700	[thread overview]
Message-ID: <20060510154702.GA28938@twiddle.net> (raw)
In-Reply-To: <17505.26159.807484.477212@cargo.ozlabs.ibm.com>

On Wed, May 10, 2006 at 02:03:59PM +1000, Paul Mackerras wrote:
> With this patch, 64-bit powerpc uses __thread for per-cpu variables.

How do you plan to address the compiler optimizing

	__thread int foo;
	{
	  use(foo);
	  schedule();
	  use(foo);
	}

into

	{
	  int *tmp = &foo;	// tls arithmetic here
	  use(*tmp);
	  schedule();
	  use(*tmp);
	}

Across the schedule, we may have changed cpus, making the cached
address invalid.

r~