When exceptions or irq are about to resume userspace, if
the task needs to be rescheduled, the arch low level code
calls schedule() directly.

If we call it, it is because we have the TIF_RESCHED flag:

- It can be set after random local calls to set_need_resched()
(RCU, drm, ...)

- A wake up happened and the CPU needs preemption. This can
  happen in several ways:

    * Remotely: the remote waking CPU has set TIF_RESCHED and send the
      wakee an IPI to schedule the new task.
    * Remotely enqueued: the remote waking CPU sends an IPI to the target
      and the wake up is made by the target.
    * Locally: waking CPU == wakee CPU and the wakeup is done locally.
      set_need_resched() is called without IPI.

In the case of local and remotely enqueued wake ups, the tick can
be restarted when we enqueue the new task and RCU can exit the
extended quiescent state at the same time. Then by the time we reach
irq exit path and we call schedule, we are not in RCU user mode.

But if we call schedule() only because something called set_need_resched(),
RCU may still be in user mode when we reach schedule.

Also if a wake up is done remotely, the CPU might see the TIF_RESCHED
flag and call schedule while the IPI has not yet happen to restart the
tick and exit RCU user mode.

We need to manually protect against these corner cases.

Create a new API schedule_user() that calls schedule() inside
rcu_user_exit()-rcu_user_enter() in order to protect it. Archs
will need to rely on it now to implement user preemption safely.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

When an exception or an irq exits, and we are going to resume into
interrupted kernel code, the low level architecture code calls
preempt_schedule_irq() if there is a need to reschedule.

If the interrupt/exception occured between a call to rcu_user_enter()
(from syscall exit, exception exit, do_notify_resume exit, ...) and
a real resume to userspace (iret,...), preempt_schedule_irq() can be
called whereas RCU thinks we are in userspace. But preempt_schedule_irq()
is going to run kernel code and may be some RCU read side critical
section. We must exit the userspace extended quiescent state before
we call it.

To solve this, just call rcu_user_exit() in the beginning of
preempt_schedule_irq().
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

Add necessary hooks to x86 exception for userspace
RCU extended quiescent state support.

This includes traps, page fault, debug exceptions, etc...
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

There is some unnatural label based layout in this function.
Convert the unnecessary goto to readable conditional blocks.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>

Add syscall slow path hooks to notify syscall entry
and exit on CPUs that want to support userspace RCU
extended quiescent state.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

Clear the syscalls hook of a task when it's scheduled out so that if
the task migrates, it doesn't run the syscall slow path on a CPU
that might not need it.

Also set the syscalls hook on the next task if needed.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

By default we don't want to enter into RCU extended quiescent
state while in userspace because doing this produces some overhead
(eg: use of syscall slowpath). Set it off by default and ready to
run when some feature like adaptive tickless need it.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

Allow calls to rcu_user_enter() even if we are already
in userspace (as seen by RCU) and allow calls to rcu_user_exit()
even if we are already in the kernel.

This makes the APIs more flexible to be called from architectures.
Exception entries for example won't need to know if they come from
userspace before calling rcu_user_exit().
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

Create a new config option under the RCU menu that put
CPUs under RCU extended quiescent state (as in dynticks
idle mode) when they run in userspace. This require
some contribution from architectures to hook into kernel
and userspace boundaries.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

The current implementation of RCU_FAST_NO_HZ tries reasonably hard to rid
the current CPU of RCU callbacks.  This is appropriate when the CPU is
entering idle, where it doesn't have much useful to do anyway, but is most
definitely not what you want when transitioning to user-mode execution.
This commit therefore detects the adaptive-tick case, and refrains from
burning CPU time getting rid of RCU callbacks in that case.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

In some cases, it is necessary to enter or exit userspace-RCU-idle mode
from an interrupt handler, for example, if some other CPU sends this
CPU a resched IPI.  In this case, the current CPU would enter the IPI
handler in userspace-RCU-idle mode, but would need to exit the IPI handler
after having exited that mode.

To allow this to work, this commit adds two new APIs to TREE_RCU:

- rcu_user_enter_after_irq(). This must be called from an interrupt between
rcu_irq_enter() and rcu_irq_exit().  After the irq calls rcu_irq_exit(),
the irq handler will return into an RCU extended quiescent state.
In theory, this interrupt is never a nested interrupt, but in practice
it might interrupt softirq, which looks to RCU like a nested interrupt.

- rcu_user_exit_after_irq(). This must be called from a non-nesting
interrupt, interrupting an RCU extended quiescent state, also
between rcu_irq_enter() and rcu_irq_exit(). After the irq calls
rcu_irq_exit(), the irq handler will return in an RCU non-quiescent
state.

[ Combined with "Allow calls to rcu_exit_user_irq from nesting irqs." ]
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

RCU currently insists that only idle tasks can enter RCU idle mode, which
prohibits an adaptive tickless kernel (AKA nohz cpusets), which in turn
would mean that usermode execution would always take scheduling-clock
interrupts, even when there is only one task runnable on the CPU in
question.

This commit therefore adds rcu_user_enter() and rcu_user_exit(), which
allow non-idle tasks to enter RCU idle mode.  These are quite similar
to rcu_idle_enter() and rcu_idle_exit(), respectively, except that they
omit the idle-task checks.

[ Updated to use "user" flag rather than separate check functions. ]

[ paulmck: Updated to drop exports of new functions based on Josh's patch
  getting rid of the need for them. ]
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

Resolved conflict in kernel/sched/core.c using Peter Zijlstra's
approach from https://lkml.org/lkml/2012/9/5/585.

The conflicts between kernel/rcutree.h and kernel/rcutree_plugin.h
were due to adjacent insertions and deletions, which were resolved
by simply accepting the changes on both branches.

Merge Linux 3.6-rc7, to pick up fixes and to resolve a conflict in an
upcoming pull.
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Merge branches 'bigrt.2012.09.23a', 'doctorture.2012.09.23a', 'fixes.2012.09.23a', 'hotplug.2012.09.23a' and 'idlechop.2012.09.23a' into HEAD

bigrt.2012.09.23a contains additional commits to reduce scheduling latency
	from RCU on huge systems (many hundrends or thousands of CPUs).

doctorture.2012.09.23a contains documentation changes and rcutorture fixes.

fixes.2012.09.23a contains miscellaneous fixes.

hotplug.2012.09.23a contains CPU-hotplug-related changes.

idle.2012.09.23a fixes architectures for which RCU no longer considered
	the idle loop to be a quiescent state due to earlier
	adaptive-dynticks changes.  Affected architectures are alpha,
	cris, frv, h8300, m32r, m68k, mn10300, parisc, score, xtensa,
	and ia64.

Pull kbuild fixes from Michal Marek:
 "There are two more kbuild fixes for 3.6.

  One fixes a race between x86's archscripts target and the rule
  (re)building scripts/basic/fixdep.  The second is a fix for the
  previous attempt at fixing make firmware_install with make 3.82.
  This new solution should work with any version of GNU make"

* 'rc-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild:
  x86/kbuild: archscripts depends on scripts_basic
  firmware: fix directory creation rule matching with make 3.80

Pull hwmon subsystem fixes from Jean Delvare.

* 'hwmon-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jdelvare/staging:
  hwmon: (fam15h_power) Tweak runavg_range on resume
  hwmon: (coretemp) Use get_online_cpus to avoid races involving CPU hotplug
  hwmon: (via-cputemp) Use get_online_cpus to avoid races involving CPU hotplug

Pull SCSI fixes from James Bottomley:
 "This is a set of four essential fixes: two oops related (bnx2i,
  virtio-scsi), one data corruption related (hpsa) and one failure to
  boot due to interrupt routing issues (mpt2ss).

  Signed-off-by: James Bottomley <JBottomley@Parallels.com>"

* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
  [SCSI] hpsa: fix handling of protocol error
  [SCSI] mpt2sas: Fix for issue - Unable to boot from the drive connected to HBA
  [SCSI] bnx2i: Fixed NULL ptr deference for 1G bnx2 Linux iSCSI offload
  [SCSI] scsi: virtio-scsi: Fix address translation failure of HighMem pages used by sg list

Fix potential NULL pointer dereference in edac_unregister_sysfs() on
system boot introduced in 3.6-rc1.

Since commit 7a623c03 ("edac: rewrite the sysfs code to use struct
device") edac_mc_alloc() no longer initializes embedded kobjects in
struct mem_ctl_info.  Therefore edac_mc_free() can no longer simply
decrement a kobject reference count to free the allocated memory unless
the memory controller driver module had also called edac_mc_add_mc().

Now edac_mc_free() will check if the newly embedded struct device has
been registered with sysfs before using either the standard device
release functions or freeing the data structures itself with logic
pulled out of the error path of edac_mc_alloc().

The BUG this patch resolves for me:

  BUG: unable to handle kernel NULL pointer dereference at   (null)
  EIP is at __wake_up_common+0x1a/0x6a
  Process modprobe (pid: 933, ti=f3dc6000 task=f3db9520 task.ti=f3dc6000)
  Call Trace:
    complete_all+0x3f/0x50
    device_pm_remove+0x23/0xa2
    device_del+0x34/0x142
    edac_unregister_sysfs+0x3b/0x5c [edac_core]
    edac_mc_free+0x29/0x2f [edac_core]
    e7xxx_probe1+0x268/0x311 [e7xxx_edac]
    e7xxx_init_one+0x56/0x61 [e7xxx_edac]
    local_pci_probe+0x13/0x15
  ...

Cc: Mauro Carvalho Chehab <mchehab@redhat.com>
Cc: Shaohui Xie <Shaohui.Xie@freescale.com>
Signed-off-by: Shaun Ruffell <sruffell@digium.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

coccinelle warns about:

+ drivers/edac/edac_mc.c:429:9-23: ERROR: reference preceded by free on line 429

   421         if (mci->csrows) {
 > 422                 for (chn = 0; chn < tot_channels; chn++) {
   423                         csr = mci->csrows[chn];
   424                         if (csr) {
 > 425                                 for (chn = 0; chn < tot_channels; chn++)
   426                                          kfree(csr->channels[chn]);
   427                                  kfree(csr);
   428                          }
 > 429                          kfree(mci->csrows[i]);
   430                  }
   431                  kfree(mci->csrows);
   432          }

and that code block seem to mess things up in several ways (double free, memory
leak, out-of-bound reads etc.):

L422: The iterator "chn" and bound "tot_channels" are totally wrong. Should be
      "row" and "tot_csrows" respectively. Which means either memory leak, or
      out-of-bound reads (which if does not trigger an immediate page fault
      error, will further lead to kfree() on random addresses).

L425: The inner loop is reusing the same iterator "chn" as the outer loop,
      which could lead to premature end of the outer loop, and hence memory leak.

L429: The array index 'i' in mci->csrows[i] is a temporary value used in
      previous loops, and won't change at all in the current loop. Which
      means either out-of-bound read and possibly kfree(random number), or the
      same mci->csrows[i] get freed once and again, and possibly double free
      for the kfree(csr) in L427.

L426/L427: a kfree(csr->channels) is needed in between to avoid leaking the memory.

The buggy code was introduced by commit de3910eb ("edac: change the mem
allocation scheme to make Documentation/kobject.txt happy") in the 3.6-rc1
merge window. Fix it by freeing up resources in this order:

  free csrows[i]->channels[j]
  free csrows[i]->channels
  free csrows[i]
  free csrows

CC: Mauro Carvalho Chehab <mchehab@redhat.com>
CC: Shaun Ruffell <sruffell@digium.com>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The quirk introduced with commit
00250ec9 (hwmon: fam15h_power: fix
bogus values with current BIOSes) is not only required during driver
load but also when system resumes from suspend. The BIOS might set the
previously recommended (but unsuitable) initilization value for the
running average range register during resume.
Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Tested-by: Andreas Hartmann <andihartmann@01019freenet.de>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: stable@vger.kernel.org # 3.0+

coretemp_init loops with for_each_online_cpu, adding platform_devices
and sysfs interfaces, then calls register_hotcpu_notifier.  There is a
race if a CPU is offlined or onlined after the loop, but before
register_hotcpu_notifier.  The race might result in the absence of a
platform_device+sysfs interface for an online CPU, or the presence of
a platform_device+sysfs interface for an offline CPU.  A similar race
occurs during coretemp_exit, after the module calls
unregister_hotcpu_notifier, but before it unregisters all devices, a
CPU might offline and a device for an offline CPU will exist for a
short while.

This fix surrounds for_each_online_cpu and register_hotcpu_notifier
with get_online_cpus+put_online_cpus; and surrounds
unregister_hotcpu_notifier and device unregistering with
get_online_cpus+put_online_cpus.

Build tested.
Signed-off-by: Silas Boyd-Wickizer <sbw@mit.edu>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

via_cputemp_init loops with for_each_online_cpu, adding
platform_devices, then calls register_hotcpu_notifier.  If a CPU is
offlined between the loop and register_hotcpu_notifier, then later
onlined, via_cputemp_device_add will attempt to add platform devices
with the same ID.  A similar race occurs during via_cputemp_exit,
after the module calls unregister_hotcpu_notifier, a CPU might offline
and a device will exist for a CPU that is offline.

This fix surrounds for_each_online_cpu and register_hotcpu_notifier
with get_online_cpus+put_online_cpus; and surrounds
unregister_hotcpu_notifier and device unregistering with
get_online_cpus+put_online_cpus.

Build tested.
Signed-off-by: Silas Boyd-Wickizer <sbw@mit.edu>
Acked-by: Harald Welte <laforge@gnumonks.org>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

Traditionally, the entire idle task served as an RCU quiescent state.
But when RCU read side critical sections started appearing within the
idle loop, this traditional strategy became untenable.  The fix was to
create new RCU APIs named rcu_idle_enter() and rcu_idle_exit(), which
must be called by each architecture's idle loop so that RCU can tell
when it is safe to ignore a given idle CPU.

Unfortunately, this fix was never applied to ia64, a shortcoming remedied
by this commit.

Reported by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Cc: <stable@vger.kernel.org> # 3.3+
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

In the old times, the whole idle task was considered
as an RCU quiescent state. But as RCU became more and
more successful overtime, some RCU read side critical
section have been added even in the code of some
architectures idle tasks, for tracing for example.

So nowadays, rcu_idle_enter() and rcu_idle_exit() must
be called by the architecture to tell RCU about the part
in the idle loop that doesn't make use of rcu read side
critical sections, typically the part that puts the CPU
in low power mode.

This is necessary for RCU to find the quiescent states in
idle in order to complete grace periods.

Add this missing pair of calls in the xtensa's idle loop.
Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: <stable@vger.kernel.org> # 3.3+
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

In the old times, the whole idle task was considered
as an RCU quiescent state. But as RCU became more and
more successful overtime, some RCU read side critical
section have been added even in the code of some
architectures idle tasks, for tracing for example.

So nowadays, rcu_idle_enter() and rcu_idle_exit() must
be called by the architecture to tell RCU about the part
in the idle loop that doesn't make use of rcu read side
critical sections, typically the part that puts the CPU
in low power mode.

This is necessary for RCU to find the quiescent states in
idle in order to complete grace periods.

Add this missing pair of calls in scores's idle loop.
Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chen Liqin <liqin.chen@sunplusct.com>
Cc: Lennox Wu <lennox.wu@gmail.com>
Cc: <stable@vger.kernel.org> # 3.3+
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

In the old times, the whole idle task was considered
as an RCU quiescent state. But as RCU became more and
more successful overtime, some RCU read side critical
section have been added even in the code of some
architectures idle tasks, for tracing for example.

So nowadays, rcu_idle_enter() and rcu_idle_exit() must
be called by the architecture to tell RCU about the part
in the idle loop that doesn't make use of rcu read side
critical sections, typically the part that puts the CPU
in low power mode.

This is necessary for RCU to find the quiescent states in
idle in order to complete grace periods.

Add this missing pair of calls in the parisc's idle loop.
Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: James E.J. Bottomley <jejb@parisc-linux.org>
Cc: Helge Deller <deller@gmx.de>
Cc: Parisc <linux-parisc@vger.kernel.org>
Cc: <stable@vger.kernel.org> # 3.3+
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

In the old times, the whole idle task was considered
as an RCU quiescent state. But as RCU became more and
more successful overtime, some RCU read side critical
section have been added even in the code of some
architectures idle tasks, for tracing for example.

So nowadays, rcu_idle_enter() and rcu_idle_exit() must
be called by the architecture to tell RCU about the part
in the idle loop that doesn't make use of rcu read side
critical sections, typically the part that puts the CPU
in low power mode.

This is necessary for RCU to find the quiescent states in
idle in order to complete grace periods.

Add this missing pair of calls in the mn10300's idle loop.
Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Koichi Yasutake <yasutake.koichi@jp.panasonic.com>
Cc: <stable@vger.kernel.org> # 3.3+
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: David Howells <dhowells@redhat.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

In the old times, the whole idle task was considered
as an RCU quiescent state. But as RCU became more and
more successful overtime, some RCU read side critical
section have been added even in the code of some
architectures idle tasks, for tracing for example.

So nowadays, rcu_idle_enter() and rcu_idle_exit() must
be called by the architecture to tell RCU about the part
in the idle loop that doesn't make use of rcu read side
critical sections, typically the part that puts the CPU
in low power mode.

This is necessary for RCU to find the quiescent states in
idle in order to complete grace periods.

Add this missing pair of calls in the m68k's idle loop.
Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: m68k <linux-m68k@lists.linux-m68k.org>
Cc: <stable@vger.kernel.org> # 3.3+
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

In the old times, the whole idle task was considered
as an RCU quiescent state. But as RCU became more and
more successful overtime, some RCU read side critical
section have been added even in the code of some
architectures idle tasks, for tracing for example.

So nowadays, rcu_idle_enter() and rcu_idle_exit() must
be called by the architecture to tell RCU about the part
in the idle loop that doesn't make use of rcu read side
critical sections, typically the part that puts the CPU
in low power mode.

This is necessary for RCU to find the quiescent states in
idle in order to complete grace periods.

Add this missing pair of calls in the m32r's idle loop.
Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Hirokazu Takata <takata@linux-m32r.org>
Cc: <stable@vger.kernel.org> # 3.3+
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

In the old times, the whole idle task was considered
as an RCU quiescent state. But as RCU became more and
more successful overtime, some RCU read side critical
section have been added even in the code of some
architectures idle tasks, for tracing for example.

So nowadays, rcu_idle_enter() and rcu_idle_exit() must
be called by the architecture to tell RCU about the part
in the idle loop that doesn't make use of rcu read side
critical sections, typically the part that puts the CPU
in low power mode.

This is necessary for RCU to find the quiescent states in
idle in order to complete grace periods.

Add this missing pair of calls in the h8300's idle loop.
Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: <stable@vger.kernel.org> # 3.3+
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

In the old times, the whole idle task was considered
as an RCU quiescent state. But as RCU became more and
more successful overtime, some RCU read side critical
section have been added even in the code of some
architectures idle tasks, for tracing for example.

So nowadays, rcu_idle_enter() and rcu_idle_exit() must
be called by the architecture to tell RCU about the part
in the idle loop that doesn't make use of rcu read side
critical sections, typically the part that puts the CPU
in low power mode.

This is necessary for RCU to find the quiescent states in
idle in order to complete grace periods.

Add this missing pair of calls in the Frv's idle loop.
Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: <stable@vger.kernel.org> # 3.3+
Acked-by: David Howells <dhowells@redhat.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

In the old times, the whole idle task was considered
as an RCU quiescent state. But as RCU became more and
more successful overtime, some RCU read side critical
section have been added even in the code of some
architectures idle tasks, for tracing for example.

So nowadays, rcu_idle_enter() and rcu_idle_exit() must
be called by the architecture to tell RCU about the part
in the idle loop that doesn't make use of rcu read side
critical sections, typically the part that puts the CPU
in low power mode.

This is necessary for RCU to find the quiescent states in
idle in order to complete grace periods.

Add this missing pair of calls in the Cris's idle loop.
Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mikael Starvik <starvik@axis.com>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: Cris <linux-cris-kernel@axis.com>
Cc: <stable@vger.kernel.org> # 3.3+
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

In the old times, the whole idle task was considered
as an RCU quiescent state. But as RCU became more and
more successful overtime, some RCU read side critical
section have been added even in the code of some
architectures idle tasks, for tracing for example.

So nowadays, rcu_idle_enter() and rcu_idle_exit() must
be called by the architecture to tell RCU about the part
in the idle loop that doesn't make use of rcu read side
critical sections, typically the part that puts the CPU
in low power mode.

This is necessary for RCU to find the quiescent states in
idle in order to complete grace periods.

Add this missing pair of calls in the Alpha's idle loop.
Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Tested-by: Michael Cree <mcree@orcon.net.nz>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: alpha <linux-alpha@vger.kernel.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: <stable@vger.kernel.org> # 3.3+
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

cpu_idle() is called on the boot CPU by the init code with
preemption disabled. But the cpu_idle() function in alpha
doesn't handle this when it calls schedule() directly.

Fix it by converting it into schedule_preempt_disabled().

Also disable preemption before calling cpu_idle() from
secondary CPU entry code to stay consistent with this
state.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Tested-by: Michael Cree <mcree@orcon.net.nz>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: alpha <linux-alpha@vger.kernel.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

If arch/x86/kernel/cpuid.c is a module, a CPU might offline or online
between the for_each_online_cpu() loop and the call to
register_hotcpu_notifier in cpuid_init or the call to
unregister_hotcpu_notifier in cpuid_exit.  The potential races can
lead to leaks/duplicates, attempts to destroy non-existant devices, or
random pointer dereferences.

For example, in cpuid_exit if:

        for_each_online_cpu(cpu)
                cpuid_device_destroy(cpu);
        class_destroy(cpuid_class);
        __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
        <----- CPU onlines
        unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);

the hotcpu notifier will attempt to create a device for the
cpuid_class, which the module already destroyed.

This fix surrounds for_each_online_cpu and register_hotcpu_notifier or
unregister_hotcpu_notifier with get_online_cpus+put_online_cpus.

Tested on a VM.
Signed-off-by: Silas Boyd-Wickizer <sbw@mit.edu>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

If arch/x86/kernel/msr.c is a module, a CPU might offline or online
between the for_each_online_cpu(i) loop and the call to
register_hotcpu_notifier in msr_init or the call to
unregister_hotcpu_notifier in msr_exit. The potential races can lead
to leaks/duplicates, attempts to destroy non-existant devices, or
random pointer dereferences.

For example, in msr_init if:

        for_each_online_cpu(i) {
                err = msr_device_create(i);
                if (err != 0)
                        goto out_class;
        }
        <----- CPU offlines
        register_hotcpu_notifier(&msr_class_cpu_notifier);

and the CPU never onlines before msr_exit, then the module will never
call msr_device_destroy for the associated CPU.

This fix surrounds for_each_online_cpu and register_hotcpu_notifier or
unregister_hotcpu_notifier with get_online_cpus+put_online_cpus.

Tested on a VM.
Signed-off-by: Silas Boyd-Wickizer <sbw@mit.edu>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Rabik and Paul reported two different issues related to the same few
lines of code.

Rabik's issue is that the nr_uninterruptible migration code is wrong in
that he sees artifacts due to this (Rabik please do expand in more
detail).

Paul's issue is that this code as it stands relies on us using
stop_machine() for unplug, we all would like to remove this assumption
so that eventually we can remove this stop_machine() usage altogether.

The only reason we'd have to migrate nr_uninterruptible is so that we
could use for_each_online_cpu() loops in favour of
for_each_possible_cpu() loops, however since nr_uninterruptible() is the
only such loop and its using possible lets not bother at all.

The problem Rabik sees is (probably) caused by the fact that by
migrating nr_uninterruptible we screw rq->calc_load_active for both rqs
involved.

So don't bother with fancy migration schemes (meaning we now have to
keep using for_each_possible_cpu()) and instead fold any nr_active delta
after we migrate all tasks away to make sure we don't have any skewed
nr_active accounting.

[ paulmck: Move call to calc_load_migration to CPU_DEAD to avoid
miscounting noted by Rakib. ]
Reported-by: Rakib Mullick <rakib.mullick@gmail.com>
Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>