hotplug: Call cpu_unplug_begin() before DOWN_PREPARE

cpu_unplug_begin() should be called before CPU_DOWN_PREPARE, because
at CPU_DOWN_PREPARE cpu_active is cleared and sched_domain is
rebuilt. Otherwise the 'sync_unplug' thread will be running on the cpu
on which it's created and not bound on the cpu which is about to go
down.

I found that by an incorrect warning on smp_processor_id() called by
sync_unplug/1, and trace shows below:
(echo 1 > /sys/device/system/cpu/cpu1/online)
  bash-1664  [000]    83.136620: _cpu_down: Bind sync_unplug to cpu 1
  bash-1664  [000]    83.136623: sched_wait_task: comm=sync_unplug/1 pid=1724 prio=120
  bash-1664  [000]    83.136624: _cpu_down: Wake sync_unplug
  bash-1664  [000]    83.136629: sched_wakeup: comm=sync_unplug/1 pid=1724 prio=120 success=1 target_cpu=000

Wants to be folded back....

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Link: http://lkml.kernel.org/r/1318762607-2261-3-git-send-email-yong.zhang0@gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
ftrace-migrate-disable-tracing.patch

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
tracing: Show padding as unsigned short

RT added two bytes to trace migrate disable counting to the trace events
and used two bytes of the padding to make the change. The structures and
all were updated correctly, but the display in the event formats was
not:

cat /debug/tracing/events/sched/sched_switch/format

name: sched_switch
ID: 51
format:
	field:unsigned short common_type;	offset:0;	size:2;	signed:0;
	field:unsigned char common_flags;	offset:2;	size:1;	signed:0;
	field:unsigned char common_preempt_count;	offset:3;	size:1;	signed:0;
	field:int common_pid;	offset:4;	size:4;	signed:1;
	field:unsigned short common_migrate_disable;	offset:8;	size:2;	signed:0;
	field:int common_padding;	offset:10;	size:2;	signed:0;

The field for common_padding has the correct size and offset, but the
use of "int" might confuse some parsers (and people that are reading
it). This needs to be changed to "unsigned short".

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1321467575.4181.36.camel@frodo
Cc: stable-rt@vger.kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
migrate-disable-rt-variant.patch

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
sched: Optimize migrate_disable

Change from task_rq_lock() to raw_spin_lock(&rq->lock) to avoid a few
atomic ops. See comment on why it should be safe.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-cbz6hkl5r5mvwtx5s3tor2y6@git.kernel.org
sched: Generic migrate_disable

Make migrate_disable() be a preempt_disable() for !rt kernels. This
allows generic code to use it but still enforces that these code
sections stay relatively small.

A preemptible migrate_disable() accessible for general use would allow
people growing arbitrary per-cpu crap instead of clean these things
up.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-275i87sl8e1jcamtchmehonm@git.kernel.org
sched, rt: Fix migrate_enable() thinko

Assigning mask = tsk_cpus_allowed(p) after p->migrate_disable = 0 ensures
that we won't see a mask change.. no push/pull, we stack tasks on one CPU.

Also add a couple fields to sched_debug for the next guy.

[ Build fix from Stratos Psomadakis <psomas@gentoo.org> ]

Signed-off-by: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@us.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1314108763.6689.4.camel@marge.simson.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
sched: teach migrate_disable about atomic contexts

 <NMI>  [<ffffffff812dafd8>] spin_bug+0x94/0xa8
 [<ffffffff812db07f>] do_raw_spin_lock+0x43/0xea
 [<ffffffff814fa9be>] _raw_spin_lock_irqsave+0x6b/0x85
 [<ffffffff8106ff9e>] ? migrate_disable+0x75/0x12d
 [<ffffffff81078aaf>] ? pin_current_cpu+0x36/0xb0
 [<ffffffff8106ff9e>] migrate_disable+0x75/0x12d
 [<ffffffff81115b9d>] pagefault_disable+0xe/0x1f
 [<ffffffff81047027>] copy_from_user_nmi+0x74/0xe6
 [<ffffffff810489d7>] perf_callchain_user+0xf3/0x135

Now clearly we can't go around taking locks from NMI context, cure
this by short-circuiting migrate_disable() when we're in an atomic
context already.

Add some extra debugging to avoid things like:

  preempt_disable()
  migrate_disable();

  preempt_enable();
  migrate_enable();

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1314967297.1301.14.camel@twins
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/n/tip-wbot4vsmwhi8vmbf83hsclk6@git.kernel.org
sched: Postpone actual migration disalbe to schedule

The migrate_disable() can cause a bit of a overhead to the RT kernel,
as changing the affinity is expensive to do at every lock encountered.
As a running task can not migrate, the actual disabling of migration
does not need to occur until the task is about to schedule out.

In most cases, a task that disables migration will enable it before
it schedules making this change improve performance tremendously.

[ Frank Rowand: UP compile fix ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Clark Williams <williams@redhat.com>
Link: http://lkml.kernel.org/r/20110927124422.779693167@goodmis.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
sched: Do not compare cpu masks in scheduler

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Clark Williams <williams@redhat.com>
Link: http://lkml.kernel.org/r/20110927124423.128129033@goodmis.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
sched: Have migrate_disable ignore bounded threads

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Clark Williams <williams@redhat.com>
Link: http://lkml.kernel.org/r/20110927124423.567944215@goodmis.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
sched-clear-pf-thread-bound-on-fallback-rq.patch

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
ftrace-crap.patch

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>