On Wed, 23 Sep 2015 13:59:28 +0200 Petr Mladek <pmla...@suse.com> wrote:
> The commit 3033f14ab78c32687 ("clone: support passing tls argument via C
> rather than pt_regs magic") introduced _do_fork() that allowed to pass
> @tls parameter.
>
> The old do_fork() is defined only for architectures that are not ready
> to use this way and do not define HAVE_COPY_THREAD_TLS. But the function
> is always declared in linux/sched.h.
>
> This patch hides the declaration when the function is not defined.
>
> ..
>
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -2618,7 +2618,9 @@ extern int do_execveat(int, struct filename *,
> const char __user * const __user *,
> int);
> extern long _do_fork(unsigned long, unsigned long, unsigned long, int __user
> *, int __user *, unsigned long);
> +#ifndef CONFIG_HAVE_COPY_THREAD_TLS
> extern long do_fork(unsigned long, unsigned long, unsigned long, int __user
> *, int __user *);
> +#endif
Generally we avoid adding such ifdefs.
Downside: a compile-time error is turned into a link-time error. This
inconveniences a small number of people a small number of times.
Upside: cleaner-looking header files. This benefits a larger number of
people a larger number of times.
So it's a good tradeoff, I think.
Now there may be some special reason why do_fork() is special. If so,
you owe us a new changelog ;)
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