workqueues: Introduce new flag WQ_POWER_EFFICIENT for power oriented workqeues

Adapted for 3.4 from lsk-v3.10

Workqueues can be performance or power-oriented. Currently, most workqueues are
bound to the CPU they were created on. This gives good performance (due to cache
effects) at the cost of potentially waking up otherwise idle cores (Idle from
scheduler's perspective. Which may or may not be physically idle) just to
process some work. To save power, we can allow the work to be rescheduled on a
core that is already awake.

Workqueues created with the WQ_UNBOUND flag will allow some power savings.
However, we don't change the default behaviour of the system.  To enable
power-saving behaviour, a new config option CONFIG_WQ_POWER_EFFICIENT needs to
be turned on. This option can also be overridden by the
workqueue.power_efficient boot parameter.

tj: Updated config description and comments.  Renamed
    CONFIG_WQ_POWER_EFFICIENT to CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
workqueue: Add system wide power_efficient workqueues

Adapted for 3.4 from lsk-v3.10

This patch adds system wide workqueues aligned towards power saving. This is
done by allocating them with WQ_UNBOUND flag if 'wq_power_efficient' is set to
'true'.

tj: updated comments a bit.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Mark Brown <broonie@linaro.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
block: queue work on power efficient wq

Backport from 3.4 from lsk-v3.10

Block layer uses workqueues for multiple purposes. There is no real dependency
of scheduling these on the cpu which scheduled them.

On a idle system, it is observed that and idle cpu wakes up many times just to
service this work. It would be better if we can schedule it on a cpu which the
scheduler believes to be the most appropriate one.

This patch replaces normal workqueues with power efficient versions.
PHYLIB: queue work on system_power_efficient_wq

Adapted for 3.4 from lsk-v3.10

Phylib uses workqueues for multiple purposes. There is no real dependency of
scheduling these on the cpu which scheduled them.

On a idle system, it is observed that and idle cpu wakes up many times just to
service this work. It would be better if we can schedule it on a cpu which the
scheduler believes to be the most appropriate one.

This patch replaces system_wq with system_power_efficient_wq for PHYLIB.

Cc: David S. Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Mark Brown <broonie@linaro.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
ASoC: jack: Use power efficient workqueue

The accessory detect debounce work is not performance sensitive so let
the scheduler run it wherever is most efficient rather than in a per CPU
workqueue by using the system power efficient workqueue.

Signed-off-by: Mark Brown <broonie@linaro.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
workqueue: use new hashtable implementation

Switch workqueues to use the new hashtable implementation. This reduces the
amount of generic unrelated code in the workqueues.

This patch depends on (hashtable: introduce a small and naive)
workqueue: fix find_worker_executing_work() brekage from hashtable conversion

commit ("workqueue: use new hashtable implementation") incorrectly
made busy workers hashed by the pointer value of worker instead of
work.  This broke find_worker_executing_work() which in turn broke a
lot of fundamental operations of workqueue - non-reentrancy and
flushing among others.  The flush malfunction triggered warning in
disk event code in Fengguang's automated test.

 write_dev_root_ (3265) used greatest stack depth: 2704 bytes left
 ------------[ cut here ]------------
 WARNING: at /c/kernel-tests/src/stable/block/genhd.c:1574 disk_clear_events+0x\
cf/0x108()
 Hardware name: Bochs
 Modules linked in:
 Pid: 3328, comm: ata_id Not tainted 3.7.0-01930-gbff6343 #1167
 Call Trace:
  [<ffffffff810997c4>] warn_slowpath_common+0x83/0x9c
  [<ffffffff810997f7>] warn_slowpath_null+0x1a/0x1c
  [<ffffffff816aea77>] disk_clear_events+0xcf/0x108
  [<ffffffff811bd8be>] check_disk_change+0x27/0x59
  [<ffffffff822e48e2>] cdrom_open+0x49/0x68b
  [<ffffffff81ab0291>] idecd_open+0x88/0xb7
  [<ffffffff811be58f>] __blkdev_get+0x102/0x3ec
  [<ffffffff811bea08>] blkdev_get+0x18f/0x30f
  [<ffffffff811bebfd>] blkdev_open+0x75/0x80
  [<ffffffff8118f510>] do_dentry_open+0x1ea/0x295
  [<ffffffff8118f5f0>] finish_open+0x35/0x41
  [<ffffffff8119c720>] do_last+0x878/0xa25
  [<ffffffff8119c993>] path_openat+0xc6/0x333
  [<ffffffff8119cf37>] do_filp_open+0x38/0x86
  [<ffffffff81190170>] do_sys_open+0x6c/0xf9
  [<ffffffff8119021e>] sys_open+0x21/0x23
  [<ffffffff82c1c3d9>] system_call_fastpath+0x16/0x1b

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
workqueue: drop CPU_DYING notifier operation

Workqueue used CPU_DYING notification to mark GCWQ_DISASSOCIATED.
This was necessary because workqueue's CPU_DOWN_PREPARE happened
before other DOWN_PREPARE notifiers and workqueue needed to stay
associated across the rest of DOWN_PREPARE.

After the previous patch, workqueue's DOWN_PREPARE happens after
others and can set GCWQ_DISASSOCIATED directly.  Drop CPU_DYING and
let the trustee set GCWQ_DISASSOCIATED after disabling concurrency
management.
mm/huge_memory: use new hashtable implementation

Switch hugemem to use the new hashtable implementation. This reduces the amount of
generic unrelated code in the hugemem.

This also removes the dymanic allocation of the hash table. The size of the table is
constant so there's no point in paying the price of an extra dereference when accessing
it.

Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
net/neighbour: queue work on power efficient wq

Workqueue used in neighbour layer have no real dependency of scheduling these on
the cpu which scheduled them.

On a idle system, it is observed that an idle cpu wakes up many times just to
service this work. It would be better if we can schedule it on a cpu which the
scheduler believes to be the most appropriate one.

This patch replaces normal workqueues with power efficient versions. This
doesn't change existing behavior of code unless CONFIG_WQ_POWER_EFFICIENT is
enabled.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
rbtree: add postorder iteration functions

Postorder iteration yields all of a node's children prior to yielding the
node itself, and this particular implementation also avoids examining the
leaf links in a node after that node has been yielded.

In what I expect will be its most common usage, postorder iteration allows
the deletion of every node in an rbtree without modifying the rbtree nodes
(no _requirement_ that they be nulled) while avoiding referencing child
nodes after they have been deleted (most commonly, freed).

I have only updated zswap to use this functionality at this point, but
numerous bits of code (most notably in the filesystem drivers) use a hand
rolled postorder iteration that NULLs child links as it traverses the
tree.  Each of those instances could be replaced with this common
implementation.

1 & 2 add rbtree postorder iteration functions.
3 adds testing of the iteration to the rbtree runtime tests
4 allows building the rbtree runtime tests as builtins
5 updates zswap.

This patch:

Add postorder iteration functions for rbtree.  These are useful for safely
freeing an entire rbtree without modifying the tree at all.
rbtree: add rbtree_postorder_for_each_entry_safe() helper

Because deletion (of the entire tree) is a relatively common use of the
rbtree_postorder iteration, and because doing it safely means fiddling
with temporary storage, provide a helper to simplify postorder rbtree
iteration.

Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
Reviewed-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
Cc: David Woodhouse <David.Woodhouse@intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Michel Lespinasse <walken@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
trace/trace_stat: use rbtree postorder iteration helper instead of opencoding

Use rbtree_postorder_for_each_entry_safe() to destroy the rbtree instead
of opencoding an alternate postorder iteration that modifies the tree

Link: http://lkml.kernel.org/r/1383345566-25087-2-git-send-email-cody@linux.vnet.ibm.com

Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
rbtree: fix rbtree_postorder_for_each_entry_safe() iterator

The iterator rbtree_postorder_for_each_entry_safe() relies on pointer
underflow behavior when testing for loop termination.  In particular it
expects that

  &rb_entry(NULL, type, field)->field

is NULL.  But the result of this expression is not defined by a C standard
and some gcc versions (e.g.  4.3.4) assume the above expression can never
be equal to NULL.  The net result is an oops because the iteration is not
properly terminated.

Fix the problem by modifying the iterator to avoid pointer underflows.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Artem Bityutskiy <dedekind1@gmail.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Patrick McHardy <kaber@trash.net>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: <stable@vger.kernel.org>		[3.12.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
fs/ext4: use rbtree postorder iteration helper instead of opencoding

Use rbtree_postorder_for_each_entry_safe() to destroy the rbtree instead
of opencoding an alternate postorder iteration that modifies the tree

Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Michel Lespinasse <walken@google.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
linux: workqeue: include back missing option

accidently removed
omap: sound: soc: merge CM changes