Re: [Qemu-devel] [PATCH v2 1/3] qemu-tls.h: Add abstraction layer for TLS variables

[Peter Maydell <peter.maydell@linaro.org>]

On 28 October 2011 08:27, Markus Armbruster <armbru@redhat.com> wrote:
> Andreas Färber <afaerber@suse.de> writes:
>
>> Am 27.10.2011 13:37, schrieb Peter Maydell:
>>> + * Copyright (c) 2011 Red Hat, Inc, Linaro Limited
>>
>> The concatenation looks kind of funny. ;)
>
> I'd split into
>
>  * Copyright (c) 2011 Red Hat, Inc
>  * Copyright (c) 2011 Linaro Limited

>>> +#ifndef QEMU_TLS_GCC_H
>>> +#define QEMU_TLS_GCC_H
>>
>> Extra _GCC. But does no harm.
>
> Unless you file "unusual" under harm, which I happen to do :)

OK, I'll fix these nits and resend later this morning.

>>> +#ifdef __linux__
>>> +#define DECLARE_TLS(type, x) extern DEFINE_TLS(type, x)
>>> +#define DEFINE_TLS(type, x)  __thread __typeof__(type) tls__##x
>>> +#define get_tls(x)           tls__##x
>>> +#else
>>> +/* Dummy implementations which define plain global variables */
>>> +#define DECLARE_TLS(type, x) extern DEFINE_TLS(type, x)
>>> +#define DEFINE_TLS(type, x)  __typeof__(type) tls__##x
>>> +#define get_tls(x)           tls__##x
>>> +#endif
>
> Any particular reason for pasting tls__ onto the identifier?

It means we catch accidentally using the identifier directly
rather than via get_tls() at compile time. (That doesn't matter
for the __thread case, obviously, but does for other implementations.)
(also it means we get out of the way of the cpu_single_env macro
we define in patch 3.)

-- PMM