sync: allow async waits to be canceled

In order to allow drivers to cleanly handled teardown we need to allow them
to cancel pending async waits.  To do this cleanly, we move allocation of
sync_fence_waiter to the driver calling sync_async_wait().

Change-Id: Ifcd95648be6ec07026d67f810070a4310f099989
Signed-off-by: Erik Gilling <konkers@android.com>
Introduce timer slack controller

From: "Kirill A. Shutemov" <kirill@shutemov.name>

task_get_effective_timer_slack() returns timer slack value to be used
to configure per-task timers. It can be equal or higher than task's
timer slack value.

For now task_get_effective_timer_slack() returns timer_slack_ns of the
task. Timer slack cgroup controller will implement a bit more
sophisticated logic.

Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>

From: "Kirill A. Shutemov" <kirill@shutemov.name>

PR_GET_EFFECTIVE_TIMERSLACK allows process to know its effective timer
slack value.

Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>

From: "Kirill A. Shutemov" <kirill@shutemov.name>

Every task_struct has timer_slack_ns value. This value uses to round up
poll() and select() timeout values. This feature can be useful in
mobile environment where combined wakeups are desired.

Originally, prctl() was the only way to change timer slack value of
a process. So you was not able change timer slack value of another
process.

cgroup subsys "timer_slack" implements timer slack controller. It
provides a way to set minimal timer slack value for a group of tasks.
If a task belongs to a cgroup with minimal timer slack value higher than
task's value, cgroup's value will be applied.

Timer slack controller allows to implement setting timer slack value of
a process based on a policy. For example, you can create foreground and
background cgroups and move tasks between them based on system state.

Idea-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>

From: "Kirill A. Shutemov" <kirill@shutemov.name>

Changelog:

v10 [7 month later, thanks to A Plumber's Wish List]:
 - rebased to linux-next-20111011
v9:
 - update documentation
 - minor cleanup
v8:
 - change hiearchy rules
 - introduce timer_slack.effective_slack_ns
 - get_task_timer_slack() -> task_get_effective_timer_slack()
 - task_get_effective_timer_slack() splited in separate patch
 - implement PR_GET_EFFECTIVE_TIMERSLACK
v7:
 - totally reworked interface and rewritten from scratch
   (See Documentation/cgroups/timer_slack.txt for more information)
v6:
 - add documentation
 - use notifier_call_chain() instead of check hook
 - fix validate_change()
 - cleanup
v5:
 - -EBUSY on writing to timer_slack.min_slack_ns/max_slack_ns if a child has
   wider min-max range
v4:
 - hierarchy support
 - drop dummy_timer_slack_check()
 - workaround lockdep false (?) positive
 - allow 0 as timer slack value
v3:
 - rework interface
 - s/EXPORT_SYMBOL/EXPORT_SYMBOL_GPL/
v2:
 - fixed with CONFIG_CGROUP_TIMER_SLACK=y
v1:
 - initial revision

Kirill A. Shutemov (3):
  hrtimer: introduce effective timer slack
  hrtimer: implement PR_GET_EFFECTIVE_TIMERSLACK
  cgroups: introduce timer slack controller

 Documentation/cgroups/timer_slack.txt |   72 +++++++++++++++++++
 fs/select.c                           |    7 +--
 include/linux/cgroup_subsys.h         |    7 ++
 include/linux/prctl.h                 |    6 ++
 include/linux/sched.h                 |   10 +++
 init/Kconfig                          |    8 ++
 kernel/Makefile                       |    1 +
 kernel/cgroup_timer_slack.c           |  124 +++++++++++++++++++++++++++++++++
 kernel/fork.c                         |    4 +
 kernel/futex.c                        |    4 +-
 kernel/hrtimer.c                      |    2 +-
 kernel/sys.c                          |    3 +
 12 files changed, 240 insertions(+), 8 deletions(-)
 create mode 100644 Documentation/cgroups/timer_slack.txt
 create mode 100644 kernel/cgroup_timer_slack.c
switch the protection of percpu_counter list to spinlock

... making percpu_counter_destroy() non-blocking

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
tmpfs: fix mempolicy object leaks

This patch fixes several mempolicy leaks in the tmpfs mount logic.
These leaks are slow - on the order of one object leaked per mount
attempt.

Leak 1 (umount doesn't free mpol allocated in mount):
    while true; do
        mount -t tmpfs -o mpol=interleave,size=100M nodev /mnt
        umount /mnt
    done

Leak 2 (errors parsing remount options will leak mpol):
    mount -t tmpfs -o size=100M nodev /mnt
    while true; do
        mount -o remount,mpol=interleave,size=x /mnt 2> /dev/null
    done
    umount /mnt

Leak 3 (multiple mpol per mount leak mpol):
    while true; do
        mount -t tmpfs -o mpol=interleave,mpol=interleave,size=100M nodev /mnt
        umount /mnt
    done

This patch fixes all of the above.  I could have broken the patch into
three pieces but is seemed easier to review as one.

Signed-off-by: Greg Thelen <gthelen@google.com>
modified for Mako kernel from LKML reference

Signed-off-by: faux123 <reioux@gmail.com>