[PATCH] Add futex wrappers with error checking v2

[Torvald Riegel]

On Fri, 2015-01-09 at 12:05 +0100, Torvald Riegel wrote:
> Compared to the previous patch, this splits futex_timed_wait into two
> variants with relative and absolute timeouts, respectively.  This allows
> for removing a few cases of code duplication in pthreads code, which
> uses absolute timeouts; also, it allows us to put platform-specific code
> to go from an absolute to a relative timeout into the platform-specific
> futex abstractions.
> The latter is done by adding lll_futex_abstimed_wait.  I expect that we
> will refactor this later on, depending on how we do the lll_ parts.

This is missing a fixup I hadn't merged.  The code works as-is for the
current uses, but the docs for futed_*timed_wait claim that NULL can be
passed as timeout arg, which is not the case with this patch.  I'll fix
this with a follow-up.

> Tested on x86_64 gnu linux.  Not tested on i386 gnu linux because I get
> a build failure that doesn't seem to be related to my patch (multiple
> definitions of `_dl_addr_inside_object' and `_itoa').  I'll investigate
> the latter, and report if I see regressions due to my patch.

This seems to be due to the changes in nptl/cancellation.c.  I don't yet
know why, but will continue looking.  If anyone has a suggestion, please
let me know.