The new load average code clears rq->calc_load_active on
CPU_ONLINE. That's wrong as the new onlined CPU might have got a
scheduler tick already and accounted the delta to the stale value of
the time we offlined the CPU.

Clear the value when we cleanup the dead CPU instead. 

Also move the update of the calc_load_update time for the newly online
CPU to CPU_UP_PREPARE to avoid that the CPU plays catch up with the
stale update time value.

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

* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/peterz/linux-2.6-sched:
  sched: Fix bug in SCHED_IDLE interaction with group scheduling
  sched: Fix rt_rq->pushable_tasks initialization in init_rt_rq()
  sched: Reset sched stats on fork()
  sched_rt: Fix overload bug on rt group scheduling
  sched: Documentation/sched-rt-group: Fix style issues & bump version

Optimize cond_resched() by removing one conditional.

Currently cond_resched() checks system_state ==
SYSTEM_RUNNING in order to avoid scheduling before the
scheduler is running.

We can however, as per suggestion of Matt, use
PREEMPT_ACTIVE to accomplish that very same.

Suggested-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

init_rt_rq() initializes only rq->rt.pushable_tasks, and not the
pushable_tasks field of the passed rt_rq.  The plist is not used
uninitialized since the only pushable_tasks plists used are the
ones of root rt_rqs; anyway reinitializing the list on every group
creation corrupts the root plist, losing its previous contents.

Signed-off-by: Fabio Checconi <fabio@gandalf.sssup.it>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20090615185638.GK21741@gandalf.sssup.it>
CC: Gregory Haskins <ghaskins@novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

The sched_stat fields are currently not reset upon fork.
Ingo's recent commit 6c594c21fcb02c662f11c97be4d7d2b73060a205
did reset nr_migrations, but it didn't reset any of the
others.

This patch resets all sched_stat fields on fork.

Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <193b0f820907090457s7a3662f4gcdecdc22fcae857b@mail.gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Fixes an easily triggerable BUG() when setting process affinities.

Make sure to count the number of migratable tasks in the same place:
the root rt_rq. Otherwise the number doesn't make sense and we'll hit
the BUG in set_cpus_allowed_rt().

Also, make sure we only count tasks, not groups (this is probably
already taken care of by the fact that rt_se->nr_cpus_allowed will be 0
for groups, but be more explicit)

Tested-by: Thomas Gleixner <tglx@linutronix.de>
CC: stable@kernel.org
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Gregory Haskins <ghaskins@novell.com>
LKML-Reference: <1247067476.9777.57.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

* 'perfcounters-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (49 commits)
  perfcounter: Handle some IO return values
  perf_counter: Push perf_sample_data through the swcounter code
  perf_counter tools: Define and use our own u64, s64 etc. definitions
  perf_counter: Close race in perf_lock_task_context()
  perf_counter, x86: Improve interactions with fast-gup
  perf_counter: Simplify and fix task migration counting
  perf_counter tools: Add a data file header
  perf_counter: Update userspace callchain sampling uses
  perf_counter: Make callchain samples extensible
  perf report: Filter to parent set by default
  perf_counter tools: Handle lost events
  perf_counter: Add event overlow handling
  fs: Provide empty .set_page_dirty() aop for anon inodes
  perf_counter: tools: Makefile tweaks for 64-bit powerpc
  perf_counter: powerpc: Add processor back-end for MPC7450 family
  perf_counter: powerpc: Make powerpc perf_counter code safe for 32-bit kernels
  perf_counter: powerpc: Change how processor-specific back-ends get selected
  perf_counter: powerpc: Use unsigned long for register and constraint values
  perf_counter: powerpc: Enable use of software counters on 32-bit powerpc
  perf_counter tools: Add and use isprint()
  ...

* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  sched: Fix out of scope variable access in sched_slice()
  sched: Hide runqueues from direct refer at source code level
  sched: Remove unneeded __ref tag
  sched, x86: Fix cpufreq + sched_clock() TSC scaling

The task migrations counter was causing rare and hard to decypher
memory corruptions under load. After a day of debugging and bisection
we found that the problem was introduced with:

  3f731ca: perf_counter: Fix cpu migration counter

Turning them off fixes the crashes. Incidentally, the whole
perf_counter_task_migration() logic can be done simpler as well,
by injecting a proper sw-counter event.

This cleanup also fixed the crashes. The precise failure mode is
not completely clear yet, but we are clearly not unhappy about
having a fix ;-)

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Now that kthread_stop() can be used even if the task has already exited,
we can kill the "wait_to_die:" loop in migration_thread().  But we must
pin rq->migration_thread after creation.

Actually, I don't think CPU_UP_CANCELED or CPU_DEAD should wait for
->migration_thread exit.  Perhaps we can simplify this code a bit more.
migration_call() can set ->should_stop and forget about this thread.  But
we need a new helper in kthred.c for that.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Vitaliy Gusev <vgusev@openvz.org
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>