The only user ignores it anyway and rightfully so.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20150414203503.756060258@linutronix.deSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

The evaluation of the next timer in the nohz code is based on jiffies
while all the tick internals are nano seconds based. We have also to
convert hrtimer nanoseconds to jiffies in the !highres case. That's
just wrong and introduces interesting corner cases.

Turn it around and convert the next timer wheel timer expiry and the
rcu event to clock monotonic and base all calculations on
nanoseconds. That identifies the case where no timer is pending
clearly with an absolute expiry value of KTIME_MAX.

Makes the code more readable and gets rid of the jiffies magic in the
nohz code.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Link: http://lkml.kernel.org/r/20150414203502.184198593@linutronix.deSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

hrtimer softirq is a leftover from the initial implementation and
serves only the purpose to handle the enqueueing of already expired
timers in the high resolution timer mode. We discussed whether we
change the return value and force all start sites to handle that the
timer is already expired, but that would be a Herculean task and I'm
not sure whether its a good idea to enforce that handling on
everyone.

A simpler solution is to enforce a timer interrupt instead of raising
and scheduling a softirq. Just use the existing infrastructure to do
so and remove all the softirq leftovers.

The HRTIMER softirq enum is now unused, but kept around because trace
parsers rely on the existing numbering.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20150414203501.840834708@linutronix.deSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

Remove one CONFIG_HOTPLUG_CPU #ifdef in trade for introducing one
CONFIG_SMP #ifdef.

The CONFIG_SMP ifdef avoids declaring the per-CPU __tvec_bases storage
on UP systems since they already have boot_tvec_bases.

Also (re)add a runtime check on the base alignment -- for the paranoid
amongst us :-)
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/fdd2d35e169bdc554ffa3fe77f77716298c75ada.1427814611.git.viresh.kumar@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

There is no need to call init_timers_cpu() on every CPU hotplug event,
there is not much we need to reset.

 - Timer-lists are already empty at the end of migrate_timers().
 - timer_jiffies will be refreshed while adding a new timer, after the
   CPU is online again.
 - active_timers and all_timers can be reset from migrate_timers().
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/54a1c30ea7b805af55beb220cadf5a07a21b0a4d.1427814611.git.viresh.kumar@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

Memory for the 'tvec_base' array is allocated separately for the boot CPU (statically)
and non-boot CPUs (dynamically).

The reason is because __TIMER_INITIALIZER() needs to set ->base to a
valid pointer (because we've made NULL special, hint: lock_timer_base())
and we cannot get a compile time pointer to per-cpu entries because we
don't know where we'll map the section, even for the boot cpu.

This can be simplified a bit by statically allocating per-cpu memory.
The only disadvantage is that memory for one of the structures will stay
unused, i.e. for the boot CPU, which uses boot_tvec_bases.

This will also guarantee that tvec_base is cacheline aligned. Even
though tvec_base has ____cacheline_aligned stuck on, kzalloc_node() does
not actually respect that (but guarantees a minimum u64 alignment).
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/17cdf560f2727f687ab159707d0aa591f8a2f82d.1427814611.git.viresh.kumar@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

The "cpu" argument was kept around on the off-chance that RCU might
offload scheduler-clock interrupts.  However, this offload approach
has been replaced by NO_HZ_FULL, which offloads -all- RCU processing
from qualifying CPUs.  It is therefore time to remove the "cpu" argument
to rcu_check_callbacks(), which this commit does.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NPranith Kumar <bobby.prani@gmail.com>

The nohz full kick, which restarts the tick when any resource depend
on it, can't be executed anywhere given the operation it does on timers.
If it is called from the scheduler or timers code, chances are that
we run into a deadlock.

This is why we run the nohz full kick from an irq work. That way we make
sure that the kick runs on a virgin context.

However if that's the case when irq work runs in its own dedicated
self-ipi, things are different for the big bunch of archs that don't
support the self triggered way. In order to support them, irq works are
also handled by the timer interrupt as fallback.

Now when irq works run on the timer interrupt, the context isn't blank.
More precisely, they can run in the context of the hrtimer that runs the
tick. But the nohz kick cancels and restarts this hrtimer and cancelling
an hrtimer from itself isn't allowed. This is why we run in an endless
loop:

	Kernel panic - not syncing: Watchdog detected hard LOCKUP on cpu 2
	CPU: 2 PID: 7538 Comm: kworker/u8:8 Not tainted 3.16.0+ #34
	Workqueue: btrfs-endio-write normal_work_helper [btrfs]
	 ffff880244c06c88 000000001b486fe1 ffff880244c06bf0 ffffffff8a7f1e37
	 ffffffff8ac52a18 ffff880244c06c78 ffffffff8a7ef928 0000000000000010
	 ffff880244c06c88 ffff880244c06c20 000000001b486fe1 0000000000000000
	Call Trace:
	 <NMI[<ffffffff8a7f1e37>] dump_stack+0x4e/0x7a
	 [<ffffffff8a7ef928>] panic+0xd4/0x207
	 [<ffffffff8a1450e8>] watchdog_overflow_callback+0x118/0x120
	 [<ffffffff8a186b0e>] __perf_event_overflow+0xae/0x350
	 [<ffffffff8a184f80>] ? perf_event_task_disable+0xa0/0xa0
	 [<ffffffff8a01a4cf>] ? x86_perf_event_set_period+0xbf/0x150
	 [<ffffffff8a187934>] perf_event_overflow+0x14/0x20
	 [<ffffffff8a020386>] intel_pmu_handle_irq+0x206/0x410
	 [<ffffffff8a01937b>] perf_event_nmi_handler+0x2b/0x50
	 [<ffffffff8a007b72>] nmi_handle+0xd2/0x390
	 [<ffffffff8a007aa5>] ? nmi_handle+0x5/0x390
	 [<ffffffff8a0cb7f8>] ? match_held_lock+0x8/0x1b0
	 [<ffffffff8a008062>] default_do_nmi+0x72/0x1c0
	 [<ffffffff8a008268>] do_nmi+0xb8/0x100
	 [<ffffffff8a7ff66a>] end_repeat_nmi+0x1e/0x2e
	 [<ffffffff8a0cb7f8>] ? match_held_lock+0x8/0x1b0
	 [<ffffffff8a0cb7f8>] ? match_held_lock+0x8/0x1b0
	 [<ffffffff8a0cb7f8>] ? match_held_lock+0x8/0x1b0
	 <<EOE><IRQ[<ffffffff8a0ccd2f>] lock_acquired+0xaf/0x450
	 [<ffffffff8a0f74c5>] ? lock_hrtimer_base.isra.20+0x25/0x50
	 [<ffffffff8a7fc678>] _raw_spin_lock_irqsave+0x78/0x90
	 [<ffffffff8a0f74c5>] ? lock_hrtimer_base.isra.20+0x25/0x50
	 [<ffffffff8a0f74c5>] lock_hrtimer_base.isra.20+0x25/0x50
	 [<ffffffff8a0f7723>] hrtimer_try_to_cancel+0x33/0x1e0
	 [<ffffffff8a0f78ea>] hrtimer_cancel+0x1a/0x30
	 [<ffffffff8a109237>] tick_nohz_restart+0x17/0x90
	 [<ffffffff8a10a213>] __tick_nohz_full_check+0xc3/0x100
	 [<ffffffff8a10a25e>] nohz_full_kick_work_func+0xe/0x10
	 [<ffffffff8a17c884>] irq_work_run_list+0x44/0x70
	 [<ffffffff8a17c8da>] irq_work_run+0x2a/0x50
	 [<ffffffff8a0f700b>] update_process_times+0x5b/0x70
	 [<ffffffff8a109005>] tick_sched_handle.isra.21+0x25/0x60
	 [<ffffffff8a109b81>] tick_sched_timer+0x41/0x60
	 [<ffffffff8a0f7aa2>] __run_hrtimer+0x72/0x470
	 [<ffffffff8a109b40>] ? tick_sched_do_timer+0xb0/0xb0
	 [<ffffffff8a0f8707>] hrtimer_interrupt+0x117/0x270
	 [<ffffffff8a034357>] local_apic_timer_interrupt+0x37/0x60
	 [<ffffffff8a80010f>] smp_apic_timer_interrupt+0x3f/0x50
	 [<ffffffff8a7fe52f>] apic_timer_interrupt+0x6f/0x80

To fix this we force non-lazy irq works to run on irq work self-IPIs
when available. That ability of the arch to trigger irq work self IPIs
is available with arch_irq_work_has_interrupt().
Reported-by: NCatalin Iacob <iacobcatalin@gmail.com>
Reported-by: NDave Jones <davej@redhat.com>
Acked-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

Convert uses of __get_cpu_var for creating a address from a percpu
offset to this_cpu_ptr.

The two cases where get_cpu_var is used to actually access a percpu
variable are changed to use this_cpu_read/raw_cpu_read.
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NChristoph Lameter <cl@linux.com>
Signed-off-by: NTejun Heo <tj@kernel.org>

When a timer is enqueued or modified on a dynticks target, that CPU
must re-evaluate the next tick to service that timer.

The tick re-evaluation is performed by an IPI kick on the target.
Now while we correctly call wake_up_nohz_cpu() from add_timer_on(), the
mod_timer*() API family doesn't support so well dynticks targets.

The reason for this is likely that __mod_timer() isn't supposed to
select an idle target for a timer, unless that target is the current
CPU, in which case a dynticks idle kick isn't actually needed.

But there is a small race window lurking behind that assumption: the
elected target has all the time to turn dynticks idle between the call
to get_nohz_timer_target() and the locking of its base. Hence a risk
that we enqueue a timer on a dynticks idle destination without kicking
it. As a result, the timer might be serviced too late in the future.

Also a target elected by __mod_timer() can be in full dynticks mode
and thus require to be kicked as well. And unlike idle dynticks, this
concern both local and remote targets.

To fix this whole issue, lets centralize the dynticks kick to
internal_add_timer() so that it is well handled for all sort of timer
enqueue. Even timer migration is concerned so that a full dynticks target
is correctly kicked as needed when timers are migrating to it.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/1403393357-2070-3-git-send-email-fweisbec@gmail.comSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

Timers are serviced by the tick. But when a timer is enqueued on a
dynticks target, we need to kick it in order to make it reconsider the
next tick to schedule to correctly handle the timer's expiring time.

Now while this kick is correctly performed for add_timer_on(), the
mod_timer*() family has been a bit neglected.

To prepare for fixing this, we need internal_add_timer() to be able to
resolve the CPU target associated to a timer's object 'base' so that the
kick can be centralized there.

This can't be passed as an argument as not all the callers know the CPU
number of a timer's base. So lets store it in the struct tvec_base to
resolve the CPU without much overhead. It is set once for good at every
CPU's first boot.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/1403393357-2070-2-git-send-email-fweisbec@gmail.comSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

Except for Kconfig.HZ. That needs a separate treatment.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

On architectures with sizeof(int) < sizeof (long), the
computation of mask inside apply_slack() can be undefined if the
computed bit is > 32.

E.g. with: expires = 0xffffe6f5 and slack = 25, we get:

expires_limit = 0x20000000e
bit = 33
mask = (1 << 33) - 1  /* undefined */

On x86, mask becomes 1 and and the slack is not applied properly.
On s390, mask is -1, expires is set to 0 and the timer fires immediately.

Use 1UL << bit to solve that issue.
Suggested-by: NDeborah Townsend <dstownse@us.ibm.com>
Signed-off-by: NJiri Bohac <jbohac@suse.cz>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20140418152310.GA13654@midget.suse.czSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

There are only two users of get_nohz_timer_target(): timer and hrtimer. Both
call it under same circumstances, i.e.

	#ifdef CONFIG_NO_HZ_COMMON
	       if (!pinned && get_sysctl_timer_migration() && idle_cpu(this_cpu))
	               return get_nohz_timer_target();
	#endif

So, it makes more sense to get all this as part of get_nohz_timer_target()
instead of duplicating code at two places. For this another parameter is
required to be passed to this routine, pinned.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Cc: linaro-kernel@lists.linaro.org
Cc: fweisbec@gmail.com
Cc: peterz@infradead.org
Link: http://lkml.kernel.org/r/1e1b53537217d58d48c2d7a222a9c3ac47d5b64c.1395140107.git.viresh.kumar@linaro.orgSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

We already have a variable 'head' that points to '&work_list', and so
we should use that instead wherever possible.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Cc: linaro-kernel@lists.linaro.org
Link: http://lkml.kernel.org/r/0d8645a6efc8360c4196c9797d59343abbfdcc5e.1395129136.git.viresh.kumar@linaro.orgSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

Currently we are using two lowest bit of base for internal purpose and
so they both should be zero in the allocated address. The code was
doing the right thing before this patch came in: commit c5f66e99
(timer: Implement TIMER_IRQSAFE)

Tejun probably forgot to update this piece of code which checks if the
lowest 'n' bits are zero or not and so wasn't updated according to the
new flag. Lets use TIMER_FLAG_MASK in the calculations here.

[ tglx: Massaged changelog ]
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Cc: linaro-kernel@lists.linaro.org
Cc: fweisbec@gmail.com
Cc: tj@kernel.org
Cc: peterz@infradead.org
Link: http://lkml.kernel.org/r/9144e10d7e854a0aa8a673332adec356d81a923c.1393576981.git.viresh.kumar@linaro.orgSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

timer_cpu_notify() should return NOTIFY_OK and nothing else. Anything else would
trigger a BUG_ON(). Return value of this routine is already checked correctly
but is done after issuing a call to init_timer_stats(). The right order would be
to check the error case first and then call init_timer_stats(). Lets do it.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Cc: linaro-kernel@lists.linaro.org
Cc: fweisbec@gmail.com
Cc: tj@kernel.org
Cc: peterz@infradead.org
Link: http://lkml.kernel.org/r/c439f5b6bbc2047e1662f4d523350531425bcf9d.1393576981.git.viresh.kumar@linaro.orgSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

The internal_add_timer() function updates base->next_timer only if
timer->expires < base->next_timer. This is correct, but it also makes
sense to do the same if we add the first non-deferrable timer.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Reviewed-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Tested-by: NMike Galbraith <bitbucket@online.de>

The __run_timers() function currently steps through the list one jiffy at
a time in order to update the timer wheel.  However, if the timer wheel
is empty, no adjustment is needed other than updating ->timer_jiffies.
Therefore, just before we add a timer to an empty timer wheel, we should
mark the timer wheel as being up to date.  This marking will reduce (and
perhaps eliminate) the jiffy-stepping that a future __run_timers() call
will need to do in response to some future timer posting or migration.
This commit therefore updates ->timer_jiffies for this case.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Reviewed-by: NOleg Nesterov <oleg@redhat.com>
Reviewed-by: NSteven Rostedt <rostedt@goodmis.org>
Tested-by: NMike Galbraith <bitbucket@online.de>

The __run_timers() function currently steps through the list one jiffy at
a time in order to update the timer wheel.  However, if the timer wheel
is empty, no adjustment is needed other than updating ->timer_jiffies.
Therefore, if we just emptied the timer wheel, for example, by deleting
the last timer, we should mark the timer wheel as being up to date.
This marking will reduce (and perhaps eliminate) the jiffy-stepping that
a future __run_timers() call will need to do in response to some future
timer posting or migration.  This commit therefore catches ->timer_jiffies
for this case.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Reviewed-by: NOleg Nesterov <oleg@redhat.com>
Reviewed-by: NSteven Rostedt <rostedt@goodmis.org>
Tested-by: NMike Galbraith <bitbucket@online.de>

The __run_timers() function currently steps through the list one jiffy at
a time in order to update the timer wheel.  However, if the timer wheel
is empty, no adjustment is needed other than updating ->timer_jiffies.
In this case, which is likely to be common for NO_HZ_FULL kernels, the
kernel currently incurs a large latency for no good reason.  This commit
therefore short-circuits this case.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Reviewed-by: NOleg Nesterov <oleg@redhat.com>
Reviewed-by: NSteven Rostedt <rostedt@goodmis.org>
Tested-by: NMike Galbraith <bitbucket@online.de>

Currently, the tvec_base structure's ->active_timers field tracks only
the non-deferrable timers, which means that even if ->active_timers is
zero, there might well be deferrable timers in the list.  This commit
therefore adds an ->all_timers field to track all the timers, whether
deferrable or not.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Reviewed-by: NOleg Nesterov <oleg@redhat.com>
Reviewed-by: NSteven Rostedt <rostedt@goodmis.org>
Tested-by: NMike Galbraith <bitbucket@online.de>

When a timer is enqueued or modified on a remote target, the latter is
expected to see and handle this timer on its next tick. However if the
target is idle and CONFIG_NO_HZ_IDLE=y, the CPU may be sleeping tickless
and the timer may be ignored.

wake_up_nohz_cpu() takes care of that by setting TIF_NEED_RESCHED and
sending an IPI to idle targets so that the tick is reevaluated on the
idle loop through the tick_nohz_idle_*() APIs.

Now this is all performed regardless of the power properties of the
timer. If the timer is deferrable, idle targets don't need to be woken
up. Only the next buzy tick needs to care about it, and no IPI kick
is needed for that to happen.

So lets spare the IPI on idle targets when the timer is deferrable.

Meanwhile we keep the current behaviour on full dynticks targets. We can
spare IPIs on idle full dynticks targets as well but some tricky races
against idle_cpu() must be dealt all along to make sure that the timer
is well handled after idle exit. We can deal with that later since
NO_HZ_FULL already has more important powersaving issues.
Reported-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/CAKohpomMZ0TAN2e6N76_g4ZRzxd5vZ1XfuZfxrP7GMxfTNiLVw@mail.gmail.comSigned-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

Jiffies is referenced by the linker script, so it has to be visible.

Handled both the generic and the x86 version.
Signed-off-by: NAndi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1391845930-28580-3-git-send-email-ak@linux.intel.comSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Use the helper function instead of __GFP_ZERO.
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Replace the single preempt_count() 'function' that's an lvalue with
two proper functions:

 preempt_count() - returns the preempt_count value as rvalue
 preempt_count_set() - Allows setting the preempt-count value

Also provide preempt_count_ptr() as a convenience wrapper to implement
all modifying operations.
Signed-off-by: NPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-orxrbycjozopqfhb4dxdkdvb@git.kernel.org
[ Fixed build failure. ]
Signed-off-by: NIngo Molnar <mingo@kernel.org>

The __cpuinit type of throwaway sections might have made sense
some time ago when RAM was more constrained, but now the savings
do not offset the cost and complications.  For example, the fix in
commit 5e427ec2 ("x86: Fix bit corruption at CPU resume time")
is a good example of the nasty type of bugs that can be created
with improper use of the various __init prefixes.

After a discussion on LKML[1] it was decided that cpuinit should go
the way of devinit and be phased out.  Once all the users are gone,
we can then finally remove the macros themselves from linux/init.h.

This removes all the uses of the __cpuinit macros from C files in
the core kernel directories (kernel, init, lib, mm, and include)
that don't really have a specific maintainer.

[1] https://lkml.org/lkml/2013/5/20/589Signed-off-by: NPaul Gortmaker <paul.gortmaker@windriver.com>

Direct compare of jiffies related values does not work in the wrap
around case. Replace it with time_is_after_jiffies().
Signed-off-by: NBart Van Assche <bvanassche@acm.org>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Link: http://lkml.kernel.org/r/519BC066.5080600@acm.org
Cc: stable@vger.kernel.org
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

An inactive timer's base can refer to a offline cpu's base.

In the current code, cpu_base's lock is blindly reinitialized each
time a CPU is brought up. If a CPU is brought online during the period
that another thread is trying to modify an inactive timer on that CPU
with holding its timer base lock, then the lock will be reinitialized
under its feet. This leads to following SPIN_BUG().

<0> BUG: spinlock already unlocked on CPU#3, kworker/u:3/1466
<0> lock: 0xe3ebe000, .magic: dead4ead, .owner: kworker/u:3/1466, .owner_cpu: 1
<4> [<c0013dc4>] (unwind_backtrace+0x0/0x11c) from [<c026e794>] (do_raw_spin_unlock+0x40/0xcc)
<4> [<c026e794>] (do_raw_spin_unlock+0x40/0xcc) from [<c076c160>] (_raw_spin_unlock+0x8/0x30)
<4> [<c076c160>] (_raw_spin_unlock+0x8/0x30) from [<c009b858>] (mod_timer+0x294/0x310)
<4> [<c009b858>] (mod_timer+0x294/0x310) from [<c00a5e04>] (queue_delayed_work_on+0x104/0x120)
<4> [<c00a5e04>] (queue_delayed_work_on+0x104/0x120) from [<c04eae00>] (sdhci_msm_bus_voting+0x88/0x9c)
<4> [<c04eae00>] (sdhci_msm_bus_voting+0x88/0x9c) from [<c04d8780>] (sdhci_disable+0x40/0x48)
<4> [<c04d8780>] (sdhci_disable+0x40/0x48) from [<c04bf300>] (mmc_release_host+0x4c/0xb0)
<4> [<c04bf300>] (mmc_release_host+0x4c/0xb0) from [<c04c7aac>] (mmc_sd_detect+0x90/0xfc)
<4> [<c04c7aac>] (mmc_sd_detect+0x90/0xfc) from [<c04c2504>] (mmc_rescan+0x7c/0x2c4)
<4> [<c04c2504>] (mmc_rescan+0x7c/0x2c4) from [<c00a6a7c>] (process_one_work+0x27c/0x484)
<4> [<c00a6a7c>] (process_one_work+0x27c/0x484) from [<c00a6e94>] (worker_thread+0x210/0x3b0)
<4> [<c00a6e94>] (worker_thread+0x210/0x3b0) from [<c00aad9c>] (kthread+0x80/0x8c)
<4> [<c00aad9c>] (kthread+0x80/0x8c) from [<c000ea80>] (kernel_thread_exit+0x0/0x8)

As an example, this particular crash occurred when CPU #3 is executing
mod_timer() on an inactive timer whose base is refered to offlined CPU
#2.  The code locked the timer_base corresponding to CPU #2. Before it
could proceed, CPU #2 came online and reinitialized the spinlock
corresponding to its base. Thus now CPU #3 held a lock which was
reinitialized. When CPU #3 finally ended up unlocking the old cpu_base
corresponding to CPU #2, we hit the above SPIN_BUG().

CPU #0		CPU #3				       CPU #2
------		-------				       -------
.....		 ......				      <Offline>
		mod_timer()
		 lock_timer_base
		   spin_lock_irqsave(&base->lock)

cpu_up(2)	 .....				        ......
							init_timers_cpu()
....		 .....				    	spin_lock_init(&base->lock)
.....		   spin_unlock_irqrestore(&base->lock)  ......
		   <spin_bug>

Allocation of per_cpu timer vector bases is done only once under
"tvec_base_done[]" check. In the current code, spinlock_initialization
of base->lock isn't under this check. When a CPU is up each time the
base lock is reinitialized. Move base spinlock initialization under
the check.
Signed-off-by: NTirupathi Reddy <tirupath@codeaurora.org>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1368520142-4136-1-git-send-email-tirupath@codeaurora.orgSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

Andrew Morton noted:

	akpm3:/usr/src/25> grep SYSCALL kernel/timer.c
	SYSCALL_DEFINE1(alarm, unsigned int, seconds)
	SYSCALL_DEFINE0(getpid)
	SYSCALL_DEFINE0(getppid)
	SYSCALL_DEFINE0(getuid)
	SYSCALL_DEFINE0(geteuid)
	SYSCALL_DEFINE0(getgid)
	SYSCALL_DEFINE0(getegid)
	SYSCALL_DEFINE0(gettid)
	SYSCALL_DEFINE1(sysinfo, struct sysinfo __user *, info)
	COMPAT_SYSCALL_DEFINE1(sysinfo, struct compat_sysinfo __user *, info)

	Only one of those should be in kernel/timer.c.  Who wrote this thing?

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: NStephen Rothwell <sfr@canb.auug.org.au>
Acked-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NStephen Rothwell <sfr@canb.auug.org.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The only use outside of kernel/timer.c was in kernel/compat.c, so move
compat_sys_sysinfo() next to sys_sysinfo() in kernel/timer.c.
Signed-off-by: NStephen Rothwell <sfr@canb.auug.org.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We are planning to convert the dynticks Kconfig options layout
into a choice menu. The user must be able to easily pick
any of the following implementations: constant periodic tick,
idle dynticks, full dynticks.

As this implies a mutual exclusion, the two dynticks implementions
need to converge on the selection of a common Kconfig option in order
to ease the sharing of a common infrastructure.

It would thus seem pretty natural to reuse CONFIG_NO_HZ to
that end. It already implements all the idle dynticks code
and the full dynticks depends on all that code for now.
So ideally the choice menu would propose CONFIG_NO_HZ_IDLE and
CONFIG_NO_HZ_EXTENDED then both would select CONFIG_NO_HZ.

On the other hand we want to stay backward compatible: if
CONFIG_NO_HZ is set in an older config file, we want to
enable CONFIG_NO_HZ_IDLE by default.

But we can't afford both at the same time or we run into
a circular dependency:

1) CONFIG_NO_HZ_IDLE and CONFIG_NO_HZ_EXTENDED both select
   CONFIG_NO_HZ
2) If CONFIG_NO_HZ is set, we default to CONFIG_NO_HZ_IDLE

We might be able to support that from Kconfig/Kbuild but it
may not be wise to introduce such a confusing behaviour.

So to solve this, create a new CONFIG_NO_HZ_COMMON option
which gathers the common code between idle and full dynticks
(that common code for now is simply the idle dynticks code)
and select it from their referring Kconfig.

Then we'll later create CONFIG_NO_HZ_IDLE and map CONFIG_NO_HZ
to it for backward compatibility.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
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: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>

Wake up a CPU when a timer list timer is enqueued there and
the target is part of the full dynticks range. Sending an IPI
to it makes it reconsidering the next timer to program on top
of recent updates.

This may later be improved by checking if the tick is really
stopped on the target. This would need some careful
synchronization though. So deal with such optimization later
and start simple.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
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: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>

Move the sysctl-related bits from include/linux/sched.h into
a new file: include/linux/sched/sysctl.h. Then update source
files requiring access to those bits by including the new
header file.
Signed-off-by: NClark Williams <williams@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20130207094659.06dced96@riff.lanSigned-off-by: NIngo Molnar <mingo@kernel.org>

klogd is woken up asynchronously from the tick in order
to do it safely.

However if printk is called when the tick is stopped, the reader
won't be woken up until the next interrupt, which might not fire
for a while. As a result, the user may miss some message.

To fix this, lets implement the printk tick using a lazy irq work.
This subsystem takes care of the timer tick state and can
fix up accordingly.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>

Adding two (or more) timers with large values for "expires" (they have
to reside within tv5 in the same list) leads to endless looping
between cascade() and internal_add_timer() in case CONFIG_BASE_SMALL
is one and jiffies are crossing the value 1 << 18. The bug was
introduced between 2.6.11 and 2.6.12 (and survived for quite some
time).

This patch ensures that when cascade() is called timers within tv5 are
not added endlessly to their own list again, instead they are added to
the next lower tv level tv4 (as expected).
Signed-off-by: NChristian Hildner <christian.hildner@siemens.com>
Reviewed-by: NJan Kiszka <jan.kiszka@siemens.com>
Link: http://lkml.kernel.org/r/98673C87CB31274881CFFE0B65ECC87B0F5FC1963E@DEFTHW99EA4MSX.ww902.siemens.netSigned-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org

Timer internals are protected with irq-safe locks but timer execution
isn't, so a timer being dequeued for execution and its execution
aren't atomic against IRQs.  This makes it impossible to wait for its
completion from IRQ handlers and difficult to shoot down a timer from
IRQ handlers.

This issue caused some issues for delayed_work interface.  Because
there's no way to reliably shoot down delayed_work->timer from IRQ
handlers, __cancel_delayed_work() can't share the logic to steal the
target delayed_work with cancel_delayed_work_sync(), and can only
steal delayed_works which are on queued on timer.  Similarly, the
pending mod_delayed_work() can't be used from IRQ handlers.

This patch adds a new timer flag TIMER_IRQSAFE, which makes the timer
to be executed without enabling IRQ after dequeueing such that its
dequeueing and execution are atomic against IRQ handlers.

This makes it safe to wait for the timer's completion from IRQ
handlers, for example, using del_timer_sync().  It can never be
executing on the local CPU and if executing on other CPUs it won't be
interrupted until done.

This will enable simplifying delayed_work cancel/mod interface.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: torvalds@linux-foundation.org
Cc: peterz@infradead.org
Link: http://lkml.kernel.org/r/1344449428-24962-5-git-send-email-tj@kernel.orgSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

Over time, timer initializers became messy with unnecessarily
duplicated code which are inconsistently spread across timer.h and
timer.c.

This patch cleans up timer initializers.

* timer.c::__init_timer() is renamed to do_init_timer().

* __TIMER_INITIALIZER() added.  It takes @flags and all initializers
  are wrappers around it.

* init_timer[_on_stack]_key() now take @flags.

* __init_timer[_on_stack]() added.  They take @flags and all init
  macros are wrappers around them.

* __setup_timer[_on_stack]() added.  It uses __init_timer() and takes
  @flags.  All setup macros are wrappers around the two.

Note that this patch doesn't add missing init/setup combinations -
e.g. init_timer_deferrable_on_stack().  Adding missing ones is
trivial.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: torvalds@linux-foundation.org
Cc: peterz@infradead.org
Link: http://lkml.kernel.org/r/1344449428-24962-4-git-send-email-tj@kernel.orgSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

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: NTejun 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.orgSigned-off-by: NThomas Gleixner <tglx@linutronix.de>