futex: Ensure the correct return value from futex_lock_pi()

commit 12bb3f7f1b03d5913b3f9d4236a488aa7774dfe9 upstream.

In case that futex_lock_pi() was aborted by a signal or a timeout and the
task returned without acquiring the rtmutex, but is the designated owner of
the futex due to a concurrent futex_unlock_pi() fixup_owner() is invoked to
establish consistent state. In that case it invokes fixup_pi_state_owner()
which in turn tries to acquire the rtmutex again. If that succeeds then it
does not propagate this success to fixup_owner() and futex_lock_pi()
returns -EINTR or -ETIMEOUT despite having the futex locked.

Return success from fixup_pi_state_owner() in all cases where the current
task owns the rtmutex and therefore the futex and propagate it correctly
through fixup_owner(). Fixup the other callsite which does not expect a
positive return value.

Fixes: c1e2f0eaf015 ("futex: Avoid violating the 10th rule of futex")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
[Sharan: Backported patch for kernel 4.4.y. Also folded in is a part
 of the cleanup patch d7c5ed73b19c("futex: Remove needless goto's")]
Signed-off-by: Sharan Turlapati <sturlapati@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>