Pass the PI donor task, instead of a numerical priority.

Numerical priorities are not sufficient to describe state ever since
SCHED_DEADLINE.

Annotate all sched tracepoints that are currently broken; fixing them
will bork userspace. *hate*.
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: NSteven Rostedt <rostedt@goodmis.org>
Cc: juri.lelli@arm.com
Cc: bigeasy@linutronix.de
Cc: xlpang@redhat.com
Cc: mathieu.desnoyers@efficios.com
Cc: jdesfossez@efficios.com
Cc: bristot@redhat.com
Link: http://lkml.kernel.org/r/20170323150216.353599881@infradead.orgSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

With the introduction of SCHED_DEADLINE the whole notion that priority
is a single number is gone, therefore the @prio argument to
rt_mutex_setprio() doesn't make sense anymore.

So rework the code to pass a pi_task instead.

Note this also fixes a problem with pi_top_task caching; previously we
would not set the pointer (call rt_mutex_update_top_task) if the
priority didn't change, this could lead to a stale pointer.

As for the XXX, I think its fine to use pi_task->prio, because if it
differs from waiter->prio, a PI chain update is immenent.
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: juri.lelli@arm.com
Cc: bigeasy@linutronix.de
Cc: xlpang@redhat.com
Cc: rostedt@goodmis.org
Cc: mathieu.desnoyers@efficios.com
Cc: jdesfossez@efficios.com
Cc: bristot@redhat.com
Link: http://lkml.kernel.org/r/20170323150216.303827095@infradead.orgSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

A crash happened while I was playing with deadline PI rtmutex.

    BUG: unable to handle kernel NULL pointer dereference at 0000000000000018
    IP: [<ffffffff810eeb8f>] rt_mutex_get_top_task+0x1f/0x30
    PGD 232a75067 PUD 230947067 PMD 0
    Oops: 0000 [#1] SMP
    CPU: 1 PID: 10994 Comm: a.out Not tainted

    Call Trace:
    [<ffffffff810b658c>] enqueue_task+0x2c/0x80
    [<ffffffff810ba763>] activate_task+0x23/0x30
    [<ffffffff810d0ab5>] pull_dl_task+0x1d5/0x260
    [<ffffffff810d0be6>] pre_schedule_dl+0x16/0x20
    [<ffffffff8164e783>] __schedule+0xd3/0x900
    [<ffffffff8164efd9>] schedule+0x29/0x70
    [<ffffffff8165035b>] __rt_mutex_slowlock+0x4b/0xc0
    [<ffffffff81650501>] rt_mutex_slowlock+0xd1/0x190
    [<ffffffff810eeb33>] rt_mutex_timed_lock+0x53/0x60
    [<ffffffff810ecbfc>] futex_lock_pi.isra.18+0x28c/0x390
    [<ffffffff810ed8b0>] do_futex+0x190/0x5b0
    [<ffffffff810edd50>] SyS_futex+0x80/0x180

This is because rt_mutex_enqueue_pi() and rt_mutex_dequeue_pi()
are only protected by pi_lock when operating pi waiters, while
rt_mutex_get_top_task(), will access them with rq lock held but
not holding pi_lock.

In order to tackle it, we introduce new "pi_top_task" pointer
cached in task_struct, and add new rt_mutex_update_top_task()
to update its value, it can be called by rt_mutex_setprio()
which held both owner's pi_lock and rq lock. Thus "pi_top_task"
can be safely accessed by enqueue_task_dl() under rq lock.

Originally-From: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: NXunlei Pang <xlpang@redhat.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Cc: juri.lelli@arm.com
Cc: bigeasy@linutronix.de
Cc: mathieu.desnoyers@efficios.com
Cc: jdesfossez@efficios.com
Cc: bristot@redhat.com
Link: http://lkml.kernel.org/r/20170323150216.157682758@infradead.orgSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

This can be reproduced by running rt-migrate-test:

 WARNING: CPU: 2 PID: 2195 at kernel/locking/lockdep.c:3670 lock_unpin_lock()
 unpinning an unpinned lock
 ...
 Call Trace:
  dump_stack()
  __warn()
  warn_slowpath_fmt()
  lock_unpin_lock()
  __balance_callback()
  __schedule()
  schedule()
  futex_wait_queue_me()
  futex_wait()
  do_futex()
  SyS_futex()
  do_syscall_64()
  entry_SYSCALL64_slow_path()

Revert the rq_lock_irqsave() usage here, the whole point of the
balance_callback() was to allow dropping rq->lock.
Reported-by: NFengguang Wu <fengguang.wu@intel.com>
Signed-off-by: NWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 8a8c69c3 ("sched/core: Add rq->lock wrappers")
Link: http://lkml.kernel.org/r/1489718719-3951-1-git-send-email-wanpeng.li@hotmail.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Address this case:

  WARNING: CPU: 0 PID: 2070 at ../kernel/sched/core.c:109 update_rq_clock+0x74/0x80
  rq->clock_update_flags & RQCF_UPDATED

  Call Trace:
  update_rq_clock()
  move_queued_task()
  __set_cpus_allowed_ptr()
  ...
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Add DEQUEUE_NOCLOCK to all places where we just did an
update_rq_clock() already.
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Instead of relying on deactivate_task() to call update_rq_clock() and
handling the case where it didn't happen (task_on_rq_queued),
unconditionally do update_rq_clock() and skip any further updates.

This also avoids a double update on deactivate_task() + ttwu_local().
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Since all tasks on the wake_list are woken under a single rq->lock
avoid calling update_rq_clock() for each task.
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NIngo Molnar <mingo@kernel.org>

In all cases, ENQUEUE_RESTORE should also have ENQUEUE_NOCLOCK because
DEQUEUE_SAVE will have done an update_rq_clock().
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Currently {en,de}queue_task() do an unconditional update_rq_clock().
However since we want to avoid duplicate updates, so that each
rq->lock section appears atomic in time, we need to be able to skip
these clock updates.
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NIngo Molnar <mingo@kernel.org>

The missing update_rq_clock() check can work with partial rq->lock
wrappery, since a missing wrapper can cause the warning to not be
emitted when it should have, but cannot cause the warning to trigger
when it should not have.

The duplicate update_rq_clock() check however can cause false warnings
to trigger. Therefore add more comprehensive rq->lock wrappery.
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Now that we have no missing calls, add a warning to find multiple
calls.

By having only a single update_rq_clock() call per rq-lock section,
the section appears 'atomic' wrt time.
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Pavan noticed that the following commit:

  49ee5768 ("sched/core: Optimize pick_next_task() for idle_sched_class")

... broke RT,DL balancing by robbing them of the opportinty to do new-'idle'
balancing when their last runnable task (on that runqueue) goes away.
Reported-by: NPavan Kondeti <pkondeti@codeaurora.org>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Fixes: 49ee5768 ("sched/core: Optimize pick_next_task() for idle_sched_class")
Signed-off-by: NIngo Molnar <mingo@kernel.org>

We are going to split <linux/sched/hotplug.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder <linux/sched/hotplug.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

We are going to split <linux/sched/loadavg.h> out of <linux/sched.h>, which
will have to be picked up from a couple of .c files.

Create a trivial placeholder <linux/sched/topology.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

We are going to move scheduler ABI details to <uapi/linux/sched/types.h>,
which will be used from a number of .c files.

Create empty placeholder header that maps to <linux/types.h>.

Include the new header in the files that are going to need it.
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

We are going to split <linux/sched/clock.h> out of <linux/sched.h>, which
will have to be picked up from other headers and .c files.

Create a trivial placeholder <linux/sched/clock.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

So rcupdate.h is a pretty complex header, in particular it includes
<linux/completion.h> which includes <linux/wait.h> - creating a
dependency that includes <linux/wait.h> in <linux/sched.h>,
which prevents the isolation of <linux/sched.h> from the derived
<linux/wait.h> header.

Solve part of the problem by decoupling rcupdate.h from completions:
this can be done by separating out the rcu_synchronize types and APIs,
and updating their usage sites.

Since this is a mostly RCU-internal types this will not just simplify
<linux/sched.h>'s dependencies, but will make all the hundreds of
.c files that include rcupdate.h but not completions or wait.h build
faster.

( For rcutiny this means that two dependent APIs have to be uninlined,
  but that shouldn't be much of a problem as they are rare variants. )
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

tsk_nr_cpus_allowed() too is a pretty pointless wrapper that
is not used consistently and which makes the code both harder
to read and longer as well.

So remove it - this also shrinks <linux/sched.h> a bit.
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

So the original intention of tsk_cpus_allowed() was to 'future-proof'
the field - but it's pretty ineffectual at that, because half of
the code uses ->cpus_allowed directly ...

Also, the wrapper makes the code longer than the original expression!

So just get rid of it. This also shrinks <linux/sched.h> a bit.
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

It's defined in <linux/sched.h>, but nothing outside the scheduler
uses it - so move it to the sched/core.c usage site.
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

The length of TASK_STATE_TO_CHAR_STR was still checked using the old
link-time manual error method - convert it to BUILD_BUG_ON(). This
has a couple of advantages:

 - it's more obvious what's going on

 - it reduces the size and complexity of <linux/sched.h>

 - BUILD_BUG_ON() will fail during compilation, with a clearer
   error message than the link time assert.
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Apart from adding the helper function itself, the rest of the kernel is
converted mechanically using:

  git grep -l 'atomic_inc.*mm_count' | xargs sed -i 's/atomic_inc(&\(.*\)->mm_count);/mmgrab\(\1\);/'
  git grep -l 'atomic_inc.*mm_count' | xargs sed -i 's/atomic_inc(&\(.*\)\.mm_count);/mmgrab\(\&\1\);/'

This is needed for a later patch that hooks into the helper, but might
be a worthwhile cleanup on its own.

(Michal Hocko provided most of the kerneldoc comment.)

Link: http://lkml.kernel.org/r/20161218123229.22952-1-vegard.nossum@oracle.comSigned-off-by: NVegard Nossum <vegard.nossum@oracle.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Acked-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: NDavid Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Commit:

  2f5177f0 ("sched/cgroup: Fix/cleanup cgroup teardown/init")

.. moved sched_online_group() from css_online() to css_alloc().
It exposes half-baked task group into global lists before initializing
generic cgroup stuff.

LTP testcase (third in cgroup_regression_test) written for testing
similar race in kernels 2.6.26-2.6.28 easily triggers this oops:

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
  IP: kernfs_path_from_node_locked+0x260/0x320
  CPU: 1 PID: 30346 Comm: cat Not tainted 4.10.0-rc5-test #4
  Call Trace:
  ? kernfs_path_from_node+0x4f/0x60
  kernfs_path_from_node+0x3e/0x60
  print_rt_rq+0x44/0x2b0
  print_rt_stats+0x7a/0xd0
  print_cpu+0x2fc/0xe80
  ? __might_sleep+0x4a/0x80
  sched_debug_show+0x17/0x30
  seq_read+0xf2/0x3b0
  proc_reg_read+0x42/0x70
  __vfs_read+0x28/0x130
  ? security_file_permission+0x9b/0xc0
  ? rw_verify_area+0x4e/0xb0
  vfs_read+0xa5/0x170
  SyS_read+0x46/0xa0
  entry_SYSCALL_64_fastpath+0x1e/0xad

Here the task group is already linked into the global RCU-protected 'task_groups'
list, but the css->cgroup pointer is still NULL.

This patch reverts this chunk and moves online back to css_online().
Signed-off-by: NKonstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 2f5177f0 ("sched/cgroup: Fix/cleanup cgroup teardown/init")
Link: http://lkml.kernel.org/r/148655324740.424917.5302984537258726349.stgit@buzzSigned-off-by: NIngo Molnar <mingo@kernel.org>

This is triggered during boot when CONFIG_SCHED_DEBUG is enabled:

 ------------[ cut here ]------------
 WARNING: CPU: 6 PID: 81 at kernel/sched/sched.h:812 set_next_entity+0x11d/0x380
 rq->clock_update_flags < RQCF_ACT_SKIP
 CPU: 6 PID: 81 Comm: torture_shuffle Not tainted 4.10.0+ #1
 Hardware name: LENOVO ThinkCentre M8500t-N000/SHARKBAY, BIOS FBKTC1AUS 02/16/2016
 Call Trace:
  dump_stack+0x85/0xc2
  __warn+0xcb/0xf0
  warn_slowpath_fmt+0x5f/0x80
  set_next_entity+0x11d/0x380
  set_curr_task_fair+0x2b/0x60
  do_set_cpus_allowed+0x139/0x180
  __set_cpus_allowed_ptr+0x113/0x260
  set_cpus_allowed_ptr+0x10/0x20
  torture_shuffle+0xfd/0x180
  kthread+0x10f/0x150
  ? torture_shutdown_init+0x60/0x60
  ? kthread_create_on_node+0x60/0x60
  ret_from_fork+0x31/0x40
 ---[ end trace dd94d92344cea9c6 ]---

The task is running && !queued, so there is no rq clock update before calling
set_curr_task().

This patch fixes it by updating rq clock after holding rq->lock/pi_lock
just as what other dequeue + put_prev + enqueue + set_curr story does.
Signed-off-by: NWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: NMatt Fleming <matt@codeblueprint.co.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1487749975-5994-1-git-send-email-wanpeng.li@hotmail.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

The hotplug code still triggers the warning about using a stale
rq->clock value.

Fix things up to actually run update_rq_clock() in a place where we
record the 'UPDATED' flag, and then modify the annotation to retain
this flag over the rq->lock fiddling that happens as a result of
actually migrating all the tasks elsewhere.
Reported-by: NLinus Torvalds <torvalds@linux-foundation.org>
Tested-by: NMike Galbraith <efault@gmx.de>
Tested-by: NSachin Sant <sachinp@linux.vnet.ibm.com>
Tested-by: NBorislav Petkov <bp@suse.de>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: NMatt Fleming <matt@codeblueprint.co.uk>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ross Zwisler <zwisler@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 4d25b35e ("sched/fair: Restore previous rq_flags when migrating tasks in hotplug")
Link: http://lkml.kernel.org/r/20170202155506.GX6515@twins.programming.kicks-ass.netSigned-off-by: NIngo Molnar <mingo@kernel.org>

Commit 004172bd ("sched/core: Remove unnecessary #include headers")
removed the inclusion of asm/paravirt.h which is used to get
declarations of paravirt_steal_rq_enabled and paravirt_steal_clock.

It is implicitly included on x86 but not on arm and arm64 breaking the
build if paravirtualization is used.  Since things from that header are
used directly fix the build by putting the direct inclusion back.
Signed-off-by: NMark Brown <broonie@kernel.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The check for 'running' in sched_move_task() has an unlikely() around it. That
is, it is unlikely that the task being moved is running. That use to be
true. But with a couple of recent updates, it is now likely that the task
will be running.

The first change came from ea86cb4b ("sched/cgroup: Fix
cpu_cgroup_fork() handling") that moved around the use case of
sched_move_task() in do_fork() where the call is now done after the task is
woken (hence it is running).

The second change came from 8e5bfa8c ("sched/autogroup: Do not use
autogroup->tg in zombie threads") where sched_move_task() is called by the
exit path, by the task that is exiting. Hence it too is running.
Signed-off-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Link: http://lkml.kernel.org/r/20170206110426.27ca6426@gandalf.local.homeSigned-off-by: NIngo Molnar <mingo@kernel.org>

Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Over the years sched/core.c accumulated over 50 #include lines,
40 of which are superfluous. (!)

Removing them decreases the preprocessed .c file (.i) size noticeably:

            triton:~/tip> wc -l kernel/sched/core.i

  Before:   76387 kernel/sched/core.i
  After:    75896 kernel/sched/core.i

Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

update_rq_clock_task() and update_rq_clock() we unnecessarily
spread across core.c, requiring an extra prototype line.

Move them next to each other and in the proper order.

Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Refresh the comments in the core scheduler code:

 - Capitalize sentences consistently

 - Capitalize 'CPU' consistently

 - ... and other small details.

Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

We added the 'sched_rr_timeslice_ms' SCHED_RR tuning knob in this commit:

  ce0dbbbb ("sched/rt: Add a tuning knob to allow changing SCHED_RR timeslice")

... which name suggests to users that it's in milliseconds, while in reality
it's being set in milliseconds but the result is shown in jiffies.

This is obviously confusing when HZ is not 1000, it makes it appear like the
value set failed, such as HZ=100:

  root# echo 100 > /proc/sys/kernel/sched_rr_timeslice_ms
  root# cat /proc/sys/kernel/sched_rr_timeslice_ms
  10

Fix this to be milliseconds all around.
Signed-off-by: NShile Zhang <shile.zhang@nokia.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1485612049-20923-1-git-send-email-shile.zhang@nokia.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

While in the process of initialising a root domain, if function
cpupri_init() fails the memory allocated in cpudl_init() is not
reclaimed.

Adding a new goto target to cleanup the previous initialistion of
the root_domain's dl_bw structure reclaims said memory.
Signed-off-by: NMathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1485292295-21298-2-git-send-email-mathieu.poirier@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

If function cpudl_init() fails the memory allocated for &rd->rto_mask
needs to be freed, something this patch is addressing.
Signed-off-by: NMathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1485292295-21298-1-git-send-email-mathieu.poirier@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

__migrate_task() can return with a different runqueue locked than the
one we passed as an argument. So that we can repin the lock in
migrate_tasks() (and keep the update_rq_clock() bit) we need to
restore the old rq_flags before repinning.

Note that it wouldn't be correct to change move_queued_task() to repin
because of the change of runqueue and the fact that having an
up-to-date clock on the initial rq doesn't mean the new rq has one
too.
Signed-off-by: NMatt Fleming <matt@codeblueprint.co.uk>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Bug was noticed via this warning:

  WARNING: CPU: 6 PID: 1 at kernel/sched/sched.h:804 detach_task_cfs_rq+0x8e8/0xb80
  rq->clock_update_flags < RQCF_ACT_SKIP
  Modules linked in:
  CPU: 6 PID: 1 Comm: systemd Not tainted 4.10.0-rc5-00140-g0874170baf55-dirty #1
  Hardware name: Supermicro SYS-4048B-TRFT/X10QBi, BIOS 1.0 04/11/2014
  Call Trace:
   dump_stack+0x4d/0x65
   __warn+0xcb/0xf0
   warn_slowpath_fmt+0x5f/0x80
   detach_task_cfs_rq+0x8e8/0xb80
   ? allocate_cgrp_cset_links+0x59/0x80
   task_change_group_fair+0x27/0x150
   sched_change_group+0x48/0xf0
   sched_move_task+0x53/0x150
   cpu_cgroup_attach+0x36/0x70
   cgroup_taskset_migrate+0x175/0x300
   cgroup_migrate+0xab/0xd0
   cgroup_attach_task+0xf0/0x190
   __cgroup_procs_write+0x1ed/0x2f0
   cgroup_procs_write+0x14/0x20
   cgroup_file_write+0x3f/0x100
   kernfs_fop_write+0x104/0x180
   __vfs_write+0x37/0x140
   vfs_write+0xb8/0x1b0
   SyS_write+0x55/0xc0
   do_syscall_64+0x61/0x170
   entry_SYSCALL64_slow_path+0x25/0x25
Reported-by: NIngo Molnar <mingo@kernel.org>
Reported-by: NBorislav Petkov <bp@alien8.de>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Steve noticed that when we switch from IDLE to SCHED_OTHER we fail to
take the shortcut, even though all runnable tasks are of the fair
class, because prev->sched_class != &fair_sched_class.

Since I reworked the put_prev_task() stuff, we don't really care about
prev->class here, so removing that condition will allow this case.

This increases the likely case from 78% to 98% correct for Steve's
workload.
Reported-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>
Tested-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170119174408.GN6485@twins.programming.kicks-ass.netSigned-off-by: NIngo Molnar <mingo@kernel.org>

Now that IO schedule accounting is done inside __schedule(),
io_schedule() can be split into three steps - prep, schedule, and
finish - where the schedule part doesn't need any special annotation.
This allows marking a sleep as iowait by simply wrapping an existing
blocking function with io_schedule_prepare() and io_schedule_finish().

Because task_struct->in_iowait is single bit, the caller of
io_schedule_prepare() needs to record and the pass its state to
io_schedule_finish() to be safe regarding nesting.  While this isn't
the prettiest, these functions are mostly gonna be used by core
functions and we don't want to use more space for ->in_iowait.

While at it, as it's simple to do now, reimplement io_schedule()
without unnecessarily going through io_schedule_timeout().
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: adilger.kernel@dilger.ca
Cc: jack@suse.com
Cc: kernel-team@fb.com
Cc: mingbo@fb.com
Cc: tytso@mit.edu
Link: http://lkml.kernel.org/r/1477673892-28940-3-git-send-email-tj@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

For an interface to support blocking for IOs, it must call
io_schedule() instead of schedule().  This makes it tedious to add IO
blocking to existing interfaces as the switching between schedule()
and io_schedule() is often buried deep.

As we already have a way to mark the task as IO scheduling, this can
be made easier by separating out io_schedule() into multiple steps so
that IO schedule preparation can be performed before invoking a
blocking interface and the actual accounting happens inside the
scheduler.

io_schedule_timeout() does the following three things prior to calling
schedule_timeout().

 1. Mark the task as scheduling for IO.
 2. Flush out plugged IOs.
 3. Account the IO scheduling.

done close to the actual scheduling.  This patch moves #3 into the
scheduler so that later patches can separate out preparation and
finish steps from io_schedule().
Patch-originally-by: NPeter Zijlstra <peterz@infradead.org>
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: adilger.kernel@dilger.ca
Cc: akpm@linux-foundation.org
Cc: axboe@kernel.dk
Cc: jack@suse.com
Cc: kernel-team@fb.com
Cc: mingbo@fb.com
Cc: tytso@mit.edu
Link: http://lkml.kernel.org/r/20161207204841.GA22296@htj.duckdns.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>