POSIX requires that when you claim _POSIX_CPUTIME and _POSIX_THREAD_CPUTIME,
not only the clock_* calls but also timer_* calls must support the thread and
process CPU time clocks.  This patch provides that support, building on my
recent additions to support these clocks in the POSIX clock_* interfaces.
This patch will not work without those changes, as well as the patch fixing
the timer lock-siglock deadlock problem.

The apparent pervasive changes to posix-timers.c are simply that some fields
of struct k_itimer have changed name and moved into a union.  This was
appropriate since the data structures required for the existing real-time
timer support and for the new thread/process CPU-time timers are quite
different.

The glibc patches to support CPU time clocks using the new kernel support is
in http://people.redhat.com/roland/glibc/kernel-cpuclocks.patch, and that
includes tests for the timer support (if you build glibc with NPTL).
From: Christoph Lameter <clameter@sgi.com>

  Your patch breaks the mmtimer driver because it used k_itimer values for
  its own purposes.  Here is a fix by defining an additional structure in
  k_itimer (same approach for mmtimer as the cpu timers):
From: Roland McGrath <roland@redhat.com>

Fix bug identified by Alexander Nyberg <alexn@dsv.su.se>

> The problem arises from code touching the union in alloc_posix_timer()
> which makes firing go non-zero. When firing is checked in
> posix_cpu_timer_set() it will be positive causing an infinite loop.
>
> So either the below fix or preferably move the INIT_LIST_HEAD(x) from
> alloc_posix_timer() to somewhere later where it doesn't disturb the other
> union members.

Thanks for finding this problem.  The latter is what I think is the right
solution.  This patch does that, and also removes some superfluous rezeroing.
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>