[Buildroot] [PATCH v2] openssl: fix race condition when symlink shared libs

[Ryan Barnett]

All,

On Fri, Nov 20, 2015 at 10:23 AM, Ryan Barnett
<ryan.barnett at rockwellcollins.com> wrote:
> The build-shared target depends on do_crypto and link-shared, which
> will be executed in parallel. do_crypto calls
> link_a.linux_shared -> link_a.gnu which does SYMLINK_SO; in parallel,
> link-shared calls symlink.linux_shared which also does SYMLINK_SO.
> Before the symlink is created, it is rm'ed, but there is a tiny chance
> that the second one is created after the rm has been called.
>
> Fix this by using 'ln -sf' instead of 'ln -s' so the build doesn't
> error out.
>
> Patch submitted upstream at:
>   https://bugs.gentoo.org/show_bug.cgi?id=566260

So it doesn't appear that using 'ln -sf' is a valid fix as pointed out
in the bug report on the gentoo forum:

 -- Comment #2 from SpanKY <vapier at gentoo.org> ---
 `ln -sf` is no more atomic than `rm; ln`.  there is still a window where things
 can fail.  you can easily check this:

   i=0; while [ $((i++)) -lt 500 ]; do ln -sf a b & :; done

 a good number of those will fail with:
 ln: failed to create symbolic link ‘b’: File exists

 the deps need to be fixed up

So how do we want to proceed with this? Do we revert the patch for
parallel builds for openssl?

Thanks,
-Ryan