Support six-argument syscalls from C for 32-bit x86, use generic lowlevellock-futex.h (bug 18138)

[Joseph Myers]

On Mon, 23 Mar 2015, Carlos O'Donell wrote:

> The last time I changed the 6-argument syscall code for hppa, I didn't 
> notice I'd gotten it wrong until I reran more userspace tests like
> running firefox with the new glibc.
> 
> What kind of confidence do we have here without a test that exercises
> the 6-argument syscall?

All the sem_timedwait tests (possibly tests for some other NPTL functions 
as well) exercise this code through use of lll_futex_timed_wait_bitset.

> Is it possible to add an x86-specific test to show this is working
> as intended?

The only six-argument syscall usage (inline from C, as opposed to from 
syscalls.list) is in lowlevellock-futex.h, and I think the NPTL tests 
cover that.  In fact only lll_futex_timed_wait_bitset gets used on x86 
because of .S versions of pthread_cond_* where the other lll_futex_* 
macros with six-argument syscalls get used in the C versions.

So I don't think there's any useful addition of tests possible here 
(although of course if we do get future support for tests running in some 
form of container where a test can safely change the system clock, then 
adding the original test for bug 18138 to run in such a context makes 
sense).

-- 
Joseph S. Myers
joseph@codesourcery.com