rcu: Add a module parameter to force use of expedited RCU primitives

There have been some embedded applications that would benefit from
use of expedited grace-period primitives.  In some ways, this is
similar to synchronize_net() doing either a normal or an expedited
grace period depending on lock state, but with control outside of
the kernel.

This commit therefore adds rcu_expedited boot and sysfs parameters
that cause the kernel to substitute expedited primitives for the
normal grace-period primitives.

[ paulmck: Add trace/event/rcu.h to kernel/srcu.c to avoid build error.
	   Get rid of infinite loop through contention path.]

CRs-fixed: 634363
Change-Id: I45addcb532fdaa47df3019ada3283e293ed40249
Signed-off-by: Antti P Miettinen <amiettinen@nvidia.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Git-commit: 3705b88db0d7cc4a097c32d9e554054103d3f807
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
[ joonwoop@codeaurora.org: resolved merge conflicts.]
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>

Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
rcu: Add RCU_FAST_NO_HZ tracing for idle exit

Traces of rcu_prep_idle events can be confusing because
rcu_cleanup_after_idle() does no tracing.  This commit therefore adds
this tracing.

CRs-fixed: 657837
Change-Id: I8ce6251d06e25f3ff26fe016aae456a33c40a466
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Git-commit: 2fdbb31b662787f78bb78b3e4e18f1a072058ffc
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Ramesh Gupta Guntha <rggupt@codeaurora.org>

rcu: Make RCU_FAST_NO_HZ use timer rather than hrtimer

The RCU_FAST_NO_HZ facility uses an hrtimer to wake up a CPU when
it is allowed to go into dyntick-idle mode, which is almost always
cancelled soon after.  This is not what hrtimers are good at, so
this commit switches to the timer wheel.

CRs-fixed: 657837
Change-Id: Ic528055544c929251f239c729c221cfcee539cfa
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Git-commit: 2ee3dc80660ac8285a37e662fd91b2e45c46f06a
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Ramesh Gupta Guntha <rggupt@codeaurora.org>

rcu: Make RCU_FAST_NO_HZ account for pauses out of idle

Both Steven Rostedt's new idle-capable trace macros and the RCU_NONIDLE()
macro can cause RCU to momentarily pause out of idle without the rest
of the system being involved.  This can cause rcu_prepare_for_idle()
to run through its state machine too quickly, which can in turn result
in needless scheduling-clock interrupts.

This commit therefore adds code to enable rcu_prepare_for_idle() to
distinguish between an initial entry to idle on the one hand (which needs
to advance the rcu_prepare_for_idle() state machine) and an idle reentry
due to idle-capable trace macros and RCU_NONIDLE() on the other hand
(which should avoid advancing the rcu_prepare_for_idle() state machine).
Additional state is maintained to allow the timer to be correctly reposted
when returning after a momentary pause out of idle, and even more state
is maintained to detect when new non-lazy callbacks have been enqueued
(which may require re-evaluation of the approach to idleness).

CRs-fixed: 657837
Change-Id: I7c5ef8183d42982876a50b500da080f15c61b848
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Git-commit: c57afe80db4e169135eb675acc2d241e26cc064e
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Ramesh Gupta Guntha <rggupt@codeaurora.org>

rcu: Add warning for RCU_FAST_NO_HZ timer firing

RCU_FAST_NO_HZ uses a timer to limit the time that a CPU with callbacks
can remain in dyntick-idle mode.  This timer is cancelled when the CPU
exits idle, and therefore should never fire.  However, if the timer
were migrated to some other CPU for whatever reason (1) the timer could
actually fire and (2) firing on some other CPU would fail to wake up the
CPU with callbacks, possibly resulting in sluggishness or a system hang.

This commit therfore adds a WARN_ON_ONCE() to the timer handler in order
to detect this condition.

CRs-fixed: 657837
Change-Id: Ie667bd7ee157668b2f0fca7eaf67cb746be1d674
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Git-commit: 79b9a75fb703b6a2670e46b9dc495af5bc7029b3
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Ramesh Gupta Guntha <rggupt@codeaurora.org>

rcu: Ensure that RCU_FAST_NO_HZ timers expire on correct CPU

Timers are subject to migration, which can lead to the following
system-hang scenario when CONFIG_RCU_FAST_NO_HZ=y:

1.	CPU 0 executes synchronize_rcu(), which posts an RCU callback.

2.	CPU 0 then goes idle.  It cannot immediately invoke the callback,
	but there is nothing RCU needs from ti, so it enters dyntick-idle
	mode after posting a timer.

3.	The timer gets migrated to CPU 1.

4.	CPU 0 never wakes up, so the synchronize_rcu() never returns, so
	the system hangs.

This commit fixes this problem by using mod_timer_pinned(), as suggested
by Peter Zijlstra, to ensure that the timer is actually posted on the
running CPU.

CRs-fixed: 657837
Change-Id: Id4b3d586dc08db9b9a80739c3a05163b3be69e72
Reported-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Git-commit: f511fc624642f0bb8cf65aaa28979737514d4746
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Ramesh Gupta Guntha <rggupt@codeaurora.org>

rcu: Move PREEMPT_RCU preemption to switch_to() invocation

Currently, PREEMPT_RCU readers are enqueued upon entry to the scheduler.
This is inefficient because enqueuing is required only if there is a
context switch, and entry to the scheduler does not guarantee a context
switch.

The commit therefore moves the enqueuing to immediately precede the
call to switch_to() from the scheduler.

CRs-fixed: 657837
Change-Id: I7d824196483cafb82371b978f3d995a3ab1696a0
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Linus Torvalds <torvalds@linux-foundation.org>
Git-commit: 616c310e83b872024271c915c1b9ab505b9efad9
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Ramesh Gupta Guntha <rggupt@codeaurora.org>

rcu: Make exit_rcu() more precise and consolidate

When running preemptible RCU, if a task exits in an RCU read-side
critical section having blocked within that same RCU read-side critical
section, the task must be removed from the list of tasks blocking a
grace period (perhaps the current grace period, perhaps the next grace
period, depending on timing).  The exit() path invokes exit_rcu() to
do this cleanup.

However, the current implementation of exit_rcu() needlessly does the
cleanup even if the task did not block within the current RCU read-side
critical section, which wastes time and needlessly increases the size
of the state space.  Fix this by only doing the cleanup if the current
task is actually on the list of tasks blocking some grace period.

While we are at it, consolidate the two identical exit_rcu() functions
into a single function.

CRs-fixed: 657837
Change-Id: I59504aedb12064fcd6ce03973d441b547749076a
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Linus Torvalds <torvalds@linux-foundation.org>
Git-commit: 9dd8fb16c36178df2066387d2abd44d8b4dca8c8
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
[rggupt@codeaurora.org: resolve trivial merge conflicts]
Signed-off-by: Ramesh Gupta Guntha <rggupt@codeaurora.org>

rcu: Make RCU_FAST_NO_HZ handle timer migration

The current RCU_FAST_NO_HZ assumes that timers do not migrate unless a
CPU goes offline, in which case it assumes that the CPU will have to come
out of dyntick-idle mode (cancelling the timer) in order to go offline.
This is important because when RCU_FAST_NO_HZ permits a CPU to enter
dyntick-idle mode despite having RCU callbacks pending, it posts a timer
on that CPU to force a wakeup on that CPU.  This wakeup ensures that the
CPU will eventually handle the end of the grace period, including invoking
its RCU callbacks.

However, Pascal Chapperon's test setup shows that the timer handler
rcu_idle_gp_timer_func() really does get invoked in some cases.  This is
problematic because this can cause the CPU that entered dyntick-idle
mode despite still having RCU callbacks pending to remain in
dyntick-idle mode indefinitely, which means that its RCU callbacks might
never be invoked.  This situation can result in grace-period delays or
even system hangs, which matches Pascal's observations of slow boot-up
and shutdown (https://lkml.org/lkml/2012/4/5/142).  See also the bugzilla:

	https://bugzilla.redhat.com/show_bug.cgi?id=806548

This commit therefore causes the "should never be invoked" timer handler
rcu_idle_gp_timer_func() to use smp_call_function_single() to wake up
the CPU for which the timer was intended, allowing that CPU to invoke
its RCU callbacks in a timely manner.

CRs-fixed: 657837
Change-Id: I39cc0c8bf36d2e3aa9c136e3cd399ab939daad2d
Reported-by: Pascal Chapperon <pascal.chapperon@wanadoo.fr>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Git-commit: 21e52e15666323078b8517a4312712579176b56f
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Ramesh Gupta Guntha <rggupt@codeaurora.org>

rcu: Explicitly initialize RCU_FAST_NO_HZ per-CPU variables

The current initialization of the RCU_FAST_NO_HZ per-CPU variables makes
needless and fragile assumptions about the initial value of things like
the jiffies counter.  This commit therefore explicitly initializes all of
them that are better started with a non-zero value.  It also adds some
comments describing the per-CPU state variables.

CRs-fixed: 657837
Change-Id: Ia82aae8f5441a73be7e427f5fb74ec107144fa6e
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Git-commit: 98248a0e24327bc64eb7518145c44bff7bebebc3
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Ramesh Gupta Guntha <rggupt@codeaurora.org>

rcu: Make rcu_barrier() less disruptive

The rcu_barrier() primitive interrupts each and every CPU, registering
a callback on every CPU.  Once all of these callbacks have been invoked,
rcu_barrier() knows that every callback that was registered before
the call to rcu_barrier() has also been invoked.

However, there is no point in registering a callback on a CPU that
currently has no callbacks, most especially if that CPU is in a
deep idle state.  This commit therefore makes rcu_barrier() avoid
interrupting CPUs that have no callbacks.  Doing this requires reworking
the handling of orphaned callbacks, otherwise callbacks could slip through
rcu_barrier()'s net by being orphaned from a CPU that rcu_barrier() had
not yet interrupted to a CPU that rcu_barrier() had already interrupted.
This reworking was needed anyway to take a first step towards weaning
RCU from the CPU_DYING notifier's use of stop_cpu().

CRs-fixed: 657837
Change-Id: Icb4392d9dc2cd25d9c9ea05b93ea9e2a99d24bcb
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Git-commit: b1420f1c8bfc30ecf6380a31d0f686884834b599
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Ramesh Gupta Guntha <rggupt@codeaurora.org>

timer: Fix mod_timer_pinned() header comment

The mod_timer_pinned() header comment states that it prevents timers
from being migrated to a different CPU.  This is not the case, instead,
it ensures that the timer is posted to the current CPU, but does nothing
to prevent CPU-hotplug operations from migrating the timer.

This commit therefore brings the comment header into alignment with
reality.

CRs-fixed: 657837
Change-Id: I244c4c385cd1c47df216feda7b580b2876fab723
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Git-commit: 048a0e8f5e1d94c01a5fc70f5b2f2fd2f4527326
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Ramesh Gupta Guntha <rggupt@codeaurora.org>

rcu: Update RCU_FAST_NO_HZ tracing for lazy callbacks

In the current code, a short dyntick-idle interval (where there is
at least one non-lazy callback on the CPU) and a long dyntick-idle
interval (where there are only lazy callbacks on the CPU) are traced
identically, which can be less than helpful.  This commit therefore
emits different event traces in these two cases.

CRs-fixed: 657837
Change-Id: I0392bf0b9ffe3e319bdf54e7ff77f86ce5a8f212
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Tested-by: Pascal Chapperon <pascal.chapperon@wanadoo.fr>
Git-commit: fd4b352687fd8604d49c190c4c9ea9e369fd42d5
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Ramesh Gupta Guntha <rggupt@codeaurora.org>

rcu: Move RCU_FAST_NO_HZ per-CPU variables to rcu_dynticks structure

The RCU_FAST_NO_HZ code relies on a number of per-CPU variables.
This works, but is hidden from someone scanning the data structures
in rcutree.h.  This commit therefore converts these per-CPU variables
to fields in the per-CPU rcu_dynticks structures.

CRs-fixed: 657837
Change-Id: I03e65c434b0156d4ab035421591aafb697ecd86b
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Tested-by: Pascal Chapperon <pascal.chapperon@wanadoo.fr>
Git-commit: 5955f7eecd77d6b440db278b266cfecdb72ecd00
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Ramesh Gupta Guntha <rggupt@codeaurora.org>

rcu: Precompute RCU_FAST_NO_HZ timer offsets

When a CPU is entering dyntick-idle mode, tick_nohz_stop_sched_tick()
calls rcu_needs_cpu() see if RCU needs that CPU, and, if not, computes the
next wakeup time based on the timer wheels.  Only later, when actually
entering the idle loop, rcu_prepare_for_idle() will be invoked.  In some
cases, rcu_prepare_for_idle() will post timers to wake the CPU back up.
But all for naught: The next wakeup time for the CPU has already been
computed, and posting a timer afterwards does not force that wakeup
time to be recomputed.  This means that rcu_prepare_for_idle()'s have
no effect.

This is not a problem on a busy system because something else will wake
up the CPU soon enough.  However, on lightly loaded systems, the CPU
might stay asleep for a considerable length of time.  If that CPU has
a callback that the rest of the system is waiting on, the system might
run very slowly or (in theory) even hang.

This commit avoids this problem by having rcu_needs_cpu() give
tick_nohz_stop_sched_tick() an estimate of when RCU will need the CPU
to wake back up, which tick_nohz_stop_sched_tick() takes into account
when programming the CPU's wakeup time.  An alternative approach is
for rcu_prepare_for_idle() to use hrtimers instead of normal timers,
but timers are much more efficient than are hrtimers for frequently
and repeatedly posting and cancelling a given timer, which is exactly
what RCU_FAST_NO_HZ does.

CRs-fixed: 657837
Change-Id: I45c9163678240ca0b6fcac06b025d4cdb140907c
Reported-by: Pascal Chapperon <pascal.chapperon@wanadoo.fr>
Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Tested-by: Pascal Chapperon <pascal.chapperon@wanadoo.fr>
Git-commit: aa9b16306e3243229580ff889cc59fd66bf77973
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Ramesh Gupta Guntha <rggupt@codeaurora.org>

Revert "rcu: Move PREEMPT_RCU preemption to switch_to() invocation"

This reverts commit 616c310e83b872024271c915c1b9ab505b9efad9.
(Move PREEMPT_RCU preemption to switch_to() invocation).
Testing by Sasha Levin <levinsasha928@gmail.com> showed that this
can result in deadlock due to invoking the scheduler when one of
the runqueue locks is held.  Because this commit was simply a
performance optimization, revert it.

CRs-fixed: 657837
Change-Id: Idc7a560cf2d1696d8cd7d24c99747cdca227bcc2
Reported-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Sasha Levin <levinsasha928@gmail.com>
Git-commit: cba6d0d64ee53772b285d0c0c288deefbeaf7775
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Ramesh Gupta Guntha <rggupt@codeaurora.org>

rcu: Stop rcu_do_batch() from multiplexing the "count" variable

Commit b1420f1c (Make rcu_barrier() less disruptive) rearranged the
code in rcu_do_batch(), moving the ->qlen manipulation to follow
the requeueing of the callbacks.  Unfortunately, this rearrangement
clobbered the value of the "count" local variable before the value
of rdp->qlen was adjusted, resulting in the value of rdp->qlen being
inaccurate.  This commit therefore introduces an index variable "i",
avoiding the inadvertent multiplexing.

CRs-fixed: 657837
Change-Id: I1d7eab79a8e4105b407be87be3300129c32172ae
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>
Git-commit: b41772abebc27c61dd578b76da99aa5240b4c99a
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Ramesh Gupta Guntha <rggupt@codeaurora.org>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>

Conflicts:
	kernel/rcutree.c
lib: cpu_rmap: avoid flushing all workqueues

In some cases, free_irq_cpu_rmap() is called while holding a lock (eg
rtnl).  This can lead to deadlocks, because it invokes
flush_scheduled_work() which ends up waiting for whole system workqueue
to flush, but some pending works might try to acquire the lock we are
already holding.

This commit uses reference-counting to replace
irq_run_affinity_notifiers().  It also removes
irq_run_affinity_notifiers() altogether.

[akpm@linux-foundation.org: eliminate free_cpu_rmap, rename cpu_rmap_reclaim() to cpu_rmap_release(), propagate kref_put() retval from cpu_rmap_put()]
Signed-off-by: David Decotigny <decot@googlers.com>
Reviewed-by: Ben Hutchings <bhutchings@solarflare.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Or Gerlitz <ogerlitz@mellanox.com>
Acked-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
ARM: add cpufreq transiton notifier to adjust loops_per_jiffy for smp

If CONFIG_SMP, cpufreq skips loops_per_jiffy update, because different
arch has different per-cpu loops_per_jiffy definition.

Change-Id: I3bfdf800784c9c494f873de096e3a1972f14f358
Signed-off-by: Richard Zhao <richard.zhao@linaro.org>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>

Conflicts:
	arch/arm/kernel/smp.c
tick: Upstream fixes

 * Addresses the issue of timers being scheduled on offline CPUs.

tick: Don't invoke tick_nohz_stop_sched_tick() if the cpu is offline

commit 5b39939a4 (nohz: Move ts->idle_calls incrementation into strict
idle logic) moved code out of tick_nohz_stop_sched_tick() and missed
to bail out when the cpu is offline. That's causing subsequent
failures as an offline CPU is supposed to die and not to fiddle with
nohz magic.

Return false in can_stop_idle_tick() if the cpu is offline.

Reported-and-tested-by: Jiri Kosina <jkosina@suse.cz>
Reported-and-tested-by: Prarit Bhargava <prarit@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: x86@kernel.org
Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1305132138160.2863@ionos
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

timers: Consolidate base->next_timer update

Another bunch of mindlessly copied code. All callers of
internal_add_timer() except the recascading code updates
base->next_timer.

Move this into internal_add_timer() and let the cascading code call
__internal_add_timer().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Gilad Ben-Yossef <gilad@benyossef.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20120525214819.189946224@linutronix.de

timers: Create detach_if_pending() and use it

Most callers of detach_timer() have the same pattern around
them. Check whether the timer is pending and eventually updating
base->next_timer.

Create detach_if_pending() and replace the duplicated code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Gilad Ben-Yossef <gilad@benyossef.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20120525214819.131246037@linutronix.de

timers: Add accounting of non deferrable timers

The code in get_next_timer_interrupt() is suboptimal as it has to run
through the cascade to find the next expiring timer. On a completely
idle core we should only do that when there is an active timer
enqueued and base->next_timer does not give us a fast answer.

Add accounting of the active timers to the now consolidated
attach/detach code. I deliberately avoided sanity checks because the
code is fully symetric and any fiddling with timers w/o using the API
functions will lead to cute explosions anyway. ulong is big enough
even on 32bit and if we really run into the situation to have more
than 1<<32 timers enqueued there, then we are definitely not in a
state to go idle and run through that code.

This allows us to fix another shortcoming of get_next_timer_interrupt().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Gilad Ben-Yossef <gilad@benyossef.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20120525214819.236377028@linutronix.de

timers: Improve get_next_timer_interrupt()

Gilad reported at

 http://lkml.kernel.org/r/1336056962-10465-2-git-send-email-gilad@benyossef.com

"Current timer code fails to correctly return a value meaning that
 there is no future timer event, with the result that the timer keeps
 getting re-armed in HZ one shot mode even when we could turn it off,
 generating unneeded interrupts.

 What is happening is that when __next_timer_interrupt() wishes
 to return a value that signifies "there is no future timer
 event", it returns (base->timer_jiffies + NEXT_TIMER_MAX_DELTA).

 However, the code in tick_nohz_stop_sched_tick(), which called
 __next_timer_interrupt() via get_next_timer_interrupt(),
 compares the return value to (last_jiffies + NEXT_TIMER_MAX_DELTA)
 to see if the timer needs to be re-armed.

 base->timer_jiffies != last_jiffies and so tick_nohz_stop_sched_tick()
 interperts the return value as indication that there is a distant
 future event 12 days from now and programs the timer to fire next
 after KTIME_MAX nsecs instead of avoiding to arm it. This ends up
 causing a needless interrupt once every KTIME_MAX nsecs."

Fix this by using the new active timer accounting. This avoids scans
when no active timer is enqueued completely, so we don't have to rely
on base->timer_next and base->timer_jiffies anymore.

Change-Id: I874ee5e5f837a228cebf5e6a084baf520d33cd0f
Reported-by: Gilad Ben-Yossef <gilad@benyossef.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20120525214819.317535385@linutronix.de
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
timer: Generalize timer->base flags handling

To prepare for addition of another flag, generalize timer->base flags
handling.

* Rename from TBASE_*_FLAG to TIMER_* and make them LU constants.

* Define and use TIMER_FLAG_MASK for flags masking so that multiple
  flags can be handled correctly.

* Don't dereference timer->base directly even if
  !tbase_get_deferrable().  All two such places are already passed in
  @base, so use it instead.

* Make sure tvec_base's alignment is large enough for timer->base
  flags using BUILD_BUG_ON().

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: torvalds@linux-foundation.org
Cc: peterz@infradead.org
Link: http://lkml.kernel.org/r/1344449428-24962-2-git-send-email-tj@kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Change-Id: I371295186ad8c08d243f82ec68f92344317f3e6a
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
selinux: just shut up

Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
SELinux: Fix memory leak upon loading policy

commit 8ed814602876bec9bad2649ca17f34b499357a1c upstream.

Hello.

I got below leak with linux-3.10.0-54.0.1.el7.x86_64 .

[  681.903890] kmemleak: 5538 new suspected memory leaks (see /sys/kernel/debug/kmemleak)

Below is a patch, but I don't know whether we need special handing for undoing
ebitmap_set_bit() call.
----------
>>From fe97527a90fe95e2239dfbaa7558f0ed559c0992 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: Mon, 6 Jan 2014 16:30:21 +0900
Subject: SELinux: Fix memory leak upon loading policy

Commit 2463c26d "SELinux: put name based create rules in a hashtable" did not
check return value from hashtab_insert() in filename_trans_read(). It leaks
memory if hashtab_insert() returns error.

  unreferenced object 0xffff88005c9160d0 (size 8):
    comm "systemd", pid 1, jiffies 4294688674 (age 235.265s)
    hex dump (first 8 bytes):
      57 0b 00 00 6b 6b 6b a5                          W...kkk.
    backtrace:
      [<ffffffff816604ae>] kmemleak_alloc+0x4e/0xb0
      [<ffffffff811cba5e>] kmem_cache_alloc_trace+0x12e/0x360
      [<ffffffff812aec5d>] policydb_read+0xd1d/0xf70
      [<ffffffff812b345c>] security_load_policy+0x6c/0x500
      [<ffffffff812a623c>] sel_write_load+0xac/0x750
      [<ffffffff811eb680>] vfs_write+0xc0/0x1f0
      [<ffffffff811ec08c>] SyS_write+0x4c/0xa0
      [<ffffffff81690419>] system_call_fastpath+0x16/0x1b
      [<ffffffffffffffff>] 0xffffffffffffffff

However, we should not return EEXIST error to the caller, or the systemd will
show below message and the boot sequence freezes.

  systemd[1]: Failed to load SELinux policy. Freezing.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Paul Moore <pmoore@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
ARM: make kernel oops easier to read

We don't need the offset for the first function name in each backtrace
entry; this needlessly consumes screen space.  This is virtually always
the first or second instruction in the called function.

Also, recognise stmfd instructions which include r10 as a valid stack
saving instruction, and when dumping the registers, dump six registers
per line rather than five, and fix the wrapping.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
kthread_work: wake up worker only when the worker is idle

If the worker is already executing a work item when another is queued,
we can safely skip wakeup without worrying about stalling queue thus
avoiding waking up the busy worker spuriously.  Spurious wakeups
should be fine but still isn't nice and avoiding it is trivial here.

tj: Updated description.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
ARM: 7467/1: mutex: use generic xchg-based implementation for ARMv6+

The open-coded mutex implementation for ARMv6+ cores suffers from a
severe lack of barriers, so in the uncontended case we don't actually
protect any accesses performed during the critical section.

Furthermore, the code is largely a duplication of the ARMv6+ atomic_dec
code but optimised to remove a branch instruction, as the mutex fastpath
was previously inlined. Now that this is executed out-of-line, we can
reuse the atomic access code for the locking (in fact, we use the xchg
code as this produces shorter critical sections).

This patch uses the generic xchg based implementation for mutexes on
ARMv6+, which introduces barriers to the lock/unlock operations and also
has the benefit of removing a fair amount of inline assembly code.

Cc: <stable@vger.kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Nicolas Pitre <nico@linaro.org>
Reported-by: Shan Kang <kangshan0910@gmail.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

mutex: Place lock in contended state after fastpath_lock failure

ARM recently moved to asm-generic/mutex-xchg.h for its mutex
implementation after the previous implementation was found to be missing
some crucial memory barriers. However, this has revealed some problems
running hackbench on SMP platforms due to the way in which the
MUTEX_SPIN_ON_OWNER code operates.

The symptoms are that a bunch of hackbench tasks are left waiting on an
unlocked mutex and therefore never get woken up to claim it. This boils
down to the following sequence of events:

        Task A        Task B        Task C        Lock value
0                                                     1
1       lock()                                        0
2                     lock()                          0
3                     spin(A)                         0
4       unlock()                                      1
5                                   lock()            0
6                     cmpxchg(1,0)                    0
7                     contended()                    -1
8       lock()                                        0
9       spin(C)                                       0
10                                  unlock()          1
11      cmpxchg(1,0)                                  0
12      unlock()                                      1

At this point, the lock is unlocked, but Task B is in an uninterruptible
sleep with nobody to wake it up.

This patch fixes the problem by ensuring we put the lock into the
contended state if we fail to acquire it on the fastpath, ensuring that
any blocked waiters are woken up when the mutex is released.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Chris Mason <chris.mason@fusionio.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: <stable@vger.kernel.org>
Reviewed-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-6e9lrw2avczr0617fzl5vqb8@git.kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

ARM: 7495/1: mutex: use generic atomic_dec-based implementation for ARMv6+

Commit a76d7bd96d65 ("ARM: 7467/1: mutex: use generic xchg-based
implementation for ARMv6+") removed the barrier-less, ARM-specific
mutex implementation in favour of the generic xchg-based code.

Since then, a bug was uncovered in the xchg code when running on SMP
platforms, due to interactions between the locking paths and the
MUTEX_SPIN_ON_OWNER code. This was fixed in 0bce9c46bf3b ("mutex: place
lock in contended state after fastpath_lock failure"), however, the
atomic_dec-based mutex algorithm is now marginally more efficient for
ARM (~0.5% improvement in hackbench scores on dual A15).

This patch moves ARMv6+ platforms to the atomic_dec-based mutex code.

Change-Id: I6621bcd491a75f75aa6e75adffc7e47d3632c6e6
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>

Conflicts:
	arch/arm/include/asm/mutex.h
logger: Add an enable toggle for entry storage

Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
Added fsync on/off support.

Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
fs: sync: enable fsync by default.

Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
fs: sync: add missing return if fsync is disabled from userspace.

Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
arch: Introduce smp_load_acquire(), smp_store_release()

A number of situations currently require the heavyweight smp_mb(),
even though there is no need to order prior stores against later
loads.  Many architectures have much cheaper ways to handle these
situations, but the Linux kernel currently has no portable way
to make use of them.

This commit therefore supplies smp_load_acquire() and
smp_store_release() to remedy this situation.  The new
smp_load_acquire() primitive orders the specified load against
any subsequent reads or writes, while the new smp_store_release()
primitive orders the specifed store against any prior reads or
writes.  These primitives allow array-based circular FIFOs to be
implemented without an smp_mb(), and also allow a theoretical
hole in rcu_assign_pointer() to be closed at no additional
expense on most architectures.

In addition, the RCU experience transitioning from explicit
smp_read_barrier_depends() and smp_wmb() to rcu_dereference()
and rcu_assign_pointer(), respectively resulted in substantial
improvements in readability.  It therefore seems likely that
replacing other explicit barriers with smp_load_acquire() and
smp_store_release() will provide similar benefits.  It appears
that roughly half of the explicit barriers in core kernel code
might be so replaced.

[Changelog by PaulMck]

Reviewed-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Michael Ellerman <michael@ellerman.id.au>
Cc: Michael Neuling <mikey@neuling.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Victor Kaplansky <VICTORK@il.ibm.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Link: http://lkml.kernel.org/r/20131213150640.908486364@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
bug: introduce BUILD_BUG_ON_INVALID() macro

Sometimes we want to check some expressions correctness at compile time.
"(void)(e);" or "if (e);" can be dangerous if the expression has
side-effects, and gcc sometimes generates a lot of code, even if the
expression has no effect.

This patch introduces macro BUILD_BUG_ON_INVALID() for such checks, it
forces a compilation error if expression is invalid without any extra
code.

[Cast to "long" required because sizeof does not work for bit-fields.]

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Hugh Dickins <hughd@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>
include/linux/bug.h: fix sparse warning related to BUILD_BUG_ON_INVALID

Commit ("bug: introduce BUILD_BUG_ON_INVALID() macro")
introduces this macro only when _CHECKER_ is not defined.  Define a
silent macro in the else condition to fix following sparse warning:

  mm/filemap.c:395:9: error: undefined identifier 'BUILD_BUG_ON_INVALID'
  mm/filemap.c:396:9: error: undefined identifier 'BUILD_BUG_ON_INVALID'
  mm/filemap.c:397:9: error: undefined identifier 'BUILD_BUG_ON_INVALID'
  include/linux/mm.h:419:9: error: undefined identifier 'BUILD_BUG_ON_INVALID'
  include/linux/mm.h:419:9: error: not a function <noident>

Signed-off-by: Tushar Behera <tushar.behera@linaro.org>
Acked-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
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>
compiler{,-gcc4}.h, bug.h: Remove duplicate macros

__linktime_error() does the same thing as __compiletime_error() and is
only used in bug.h.  Since the macro defines a function attribute that
will cause a failure at compile-time (not link-time), it makes more sense
to keep __compiletime_error(), which is also neatly mated with
__compiletime_warning().

Signed-off-by: Daniel Santos <daniel.santos@pobox.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Joe Perches <joe@perches.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.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>

Conflicts:
	include/linux/compiler-gcc4.h
bug.h: fix BUILD_BUG_ON macro in __CHECKER__

When __CHECKER__ is defined, we disable all of the BUILD_BUG.* macros.
However, both BUILD_BUG_ON_NOT_POWER_OF_2 and BUILD_BUG_ON was evaluating
to nothing in this case, and we want (0) since this is a function-like
macro that will be followed by a semicolon.

Signed-off-by: Daniel Santos <daniel.santos@pobox.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Joe Perches <joe@perches.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.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>