[patch 0/6] futex: Bugfixes and FUTEX_LOCK_PI2

[Thomas Gleixner]

The following series started off looking into supporting selectable clocks
for FUTEX_LOCK_PI which is hardcoded to CLOCK_REALTIME and cannot be
changed.

On the way I found two bugs related to the timeout handling:

  - The allowance for FUTEX_WAIT to use FUTEX_CLOCK_REALTIME is broken and
    never worked.

  - The recent time namespace support wreckaged FUTEX_LOCK_PI timeouts when
    the task belongs to a namespace which has an CLOCK_MONOTONIC offset.

Both should have been caught by that Gleixner dude when merging them,
but it seems he's getting old.

Not having a selectable clock for PI futexes is inconsistent because all
other interfaces have it. Unfortunately this was figured out by glibc folks
quite some time ago, but nobody told us :(

The nasty hack to support it would be to treat FUTEX_CLOCK_REALTIME inverse
for FUTEX_LOCK_PI, but that's a horrible idea. Adding a new flag to the
futex op, i.e. FUTEX_CLOCK_MONOTONIC would be possible, but that's yet
another variant which makes is harder for libraries to have a consistent
clock selection handling.

So I went the way to let FUTEX_LOCK_PI alone and to add FUTEX_LOCK_PI2
which handles the clocks the same way as the other operands.

Thoughts?

The series is also available from git:

  git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git futex

Thanks,

	tglx
---
 include/uapi/linux/futex.h |    1 
 kernel/futex.c             |   89 +++++++++++++++++++++++----------------------
 2 files changed, 47 insertions(+), 43 deletions(-)