posix-cpu-timers: Split out posix-timers_types.h

Trimming down sched.h dependencies: we don't want to include more than
the base types.

Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

posix-cpu-timers: Implement the missing timer_wait_running callback

For some unknown reason the introduction of the timer_wait_running callback
missed to fixup posix CPU timers, which went unnoticed for almost four years.
Marco reported recently that the WARN_ON() in timer_wait_running()
triggers with a posix CPU timer test case.

Posix CPU timers have two execution models for expiring timers depending on
CONFIG_POSIX_CPU_TIMERS_TASK_WORK:

1) If not enabled, the expiry happens in hard interrupt context so
spin waiting on the remote CPU is reasonably time bound.

Implement an empty stub function for that case.

2) If enabled, the expiry happens in task work before returning to user
space or guest mode. The expired timers are marked as firing and moved
from the timer queue to a local list head with sighand lock held. Once
the timers are moved, sighand lock is dropped and the expiry happens in
fully preemptible context. That means the expiring task can be scheduled
out, migrated, interrupted etc. So spin waiting on it is more than
suboptimal.

The timer wheel has a timer_wait_running() mechanism for RT, which uses
a per CPU timer-base expiry lock which is held by the expiry code and the
task waiting for the timer function to complete blocks on that lock.

This does not work in the same way for posix CPU timers as there is no
timer base and expiry for process wide timers can run on any task
belonging to that process, but the concept of waiting on an expiry lock
can be used too in a slightly different way:

- Add a mutex to struct posix_cputimers_work. This struct is per task
and used to schedule the expiry task work from the timer interrupt.

- Add a task_struct pointer to struct cpu_timer which is used to store
a the task which runs the expiry. That's filled in when the task
moves the expired timers to the local expiry list. That's not
affecting the size of the k_itimer union as there are bigger union
members already

- Let the task take the expiry mutex around the expiry function

- Let the waiter acquire a task reference with rcu_read_lock() held and
block on the expiry mutex

This avoids spin-waiting on a task which might not even be on a CPU and
works nicely for RT too.

Fixes: ec8f954a40da ("posix-timers: Use a callback for cancel synchronization on PREEMPT_RT")
Reported-by: Marco Elver <elver@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Marco Elver <elver@google.com>
Tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/87zg764ojw.ffs@tglx

task_work: Remove unnecessary include from posix_timers.h

Break a header file circular dependency by removing the unnecessary
include of task_work.h from posix_timers.h.

sched.h -> posix-timers.h
posix-timers.h -> task_work.h
task_work.h -> sched.h

Add missing includes of task_work.h to:
arch/x86/mm/tlb.c
kernel/time/posix-cpu-timers.c

Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20220309162454.123006-6-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

prlimit: do not grab the tasklist_lock

Unnecessarily grabbing the tasklist_lock can be a scalability bottleneck
for workloads that also must grab the tasklist_lock for waiting,
killing, and cloning.

The tasklist_lock was grabbed to protect tsk->sighand from disappearing
(becoming NULL). tsk->signal was already protected by holding a
reference to tsk.

update_rlimit_cpu() assumed tsk->sighand != NULL. With this commit, it
attempts to lock_task_sighand(). However, this means that
update_rlimit_cpu() can fail. This only happens when a task is exiting.
Note that during exec, sighand may *change*, but it will not be NULL.

Prior to this commit, the do_prlimit() ensured that update_rlimit_cpu()
would not fail by read locking the tasklist_lock and checking tsk->sighand
!= NULL.

If update_rlimit_cpu() fails, there may be other tasks that are not
exiting that share tsk->signal. However, the group_leader is the last
task to be released, so if we cannot update_rlimit_cpu(group_leader),
then the entire process is exiting.

The only other caller of update_rlimit_cpu() is
selinux_bprm_committing_creds(). It has tsk == current, so
update_rlimit_cpu() cannot fail (current->sighand cannot disappear
until current exits).

This change resulted in a 14% speedup on a microbenchmark where parents
kill and wait on their children, and children getpriority, setpriority,
and getrlimit.

Signed-off-by: Barret Rhoden <brho@google.com>
Link: https://lkml.kernel.org/r/20220106172041.522167-4-brho@google.com
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

posix-cpu-timers: Clear task::posix_cputimers_work in copy_process()

copy_process currently copies task_struct.posix_cputimers_work as-is. If a
timer interrupt arrives while handling clone and before dup_task_struct
completes then the child task will have:

1. posix_cputimers_work.scheduled = true
2. posix_cputimers_work.work queued.

copy_process clears task_struct.task_works, so (2) will have no effect and
posix_cpu_timers_work will never run (not to mention it doesn't make sense
for two tasks to share a common linked list).

Since posix_cpu_timers_work never runs, posix_cputimers_work.scheduled is
never cleared. Since scheduled is set, future timer interrupts will skip
scheduling work, with the ultimate result that the task will never receive
timer expirations.

Together, the complete flow is:

1. Task 1 calls clone(), enters kernel.
2. Timer interrupt fires, schedules task work on Task 1.
2a. task_struct.posix_cputimers_work.scheduled = true
2b. task_struct.posix_cputimers_work.work added to
task_struct.task_works.
3. dup_task_struct() copies Task 1 to Task 2.
4. copy_process() clears task_struct.task_works for Task 2.
5. Future timer interrupts on Task 2 see
task_struct.posix_cputimers_work.scheduled = true and skip scheduling
work.

Fix this by explicitly clearing contents of task_struct.posix_cputimers_work
in copy_process(). This was never meant to be shared or inherited across
tasks in the first place.

Fixes: 1fb497dd0030 ("posix-cpu-timers: Provide mechanisms to defer timer handling to task_work")
Reported-by: Rhys Hiltner <rhys@justin.tv>
Signed-off-by: Michael Pratt <mpratt@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20211101210615.716522-1-mpratt@google.com

posix-cpu-timers: Recalc next expiration when timer_settime() ends up not queueing

There are several scenarios that can result in posix_cpu_timer_set()
not queueing the timer but still leaving the threadgroup cputime counter
running or keeping the tick dependency around for a random amount of time.

1) If timer_settime() is called with a 0 expiration on a timer that is
already disabled, the process wide cputime counter will be started
and won't ever get a chance to be stopped by stop_process_timer()
since no timer is actually armed to be processed.

The following snippet is enough to trigger the issue.

void trigger_process_counter(void)
{
timer_t id;
struct itimerspec val = { };

timer_create(CLOCK_PROCESS_CPUTIME_ID, NULL, &id);
timer_settime(id, TIMER_ABSTIME, &val, NULL);
timer_delete(id);
}

2) If timer_settime() is called with a 0 expiration on a timer that is
already armed, the timer is dequeued but not really disarmed. So the
process wide cputime counter and the tick dependency may still remain
a while around.

The following code snippet keeps this overhead around for one week after
the timer deletion:

void trigger_process_counter(void)
{
timer_t id;
struct itimerspec val = { };

val.it_value.tv_sec = 604800;
timer_create(CLOCK_PROCESS_CPUTIME_ID, NULL, &id);
timer_settime(id, 0, &val, NULL);
timer_delete(id);
}

3) If the timer was initially deactivated, this call to timer_settime()
with an early expiration may have started the process wide cputime
counter even though the timer hasn't been queued and armed because it
has fired early and inline within posix_cpu_timer_set() itself. As a
result the process wide cputime counter may never stop until a new
timer is ever armed in the future.

The following code snippet can reproduce this:

void trigger_process_counter(void)
{
timer_t id;
struct itimerspec val = { };

signal(SIGALRM, SIG_IGN);
timer_create(CLOCK_PROCESS_CPUTIME_ID, NULL, &id);
val.it_value.tv_nsec = 1;
timer_settime(id, TIMER_ABSTIME, &val, NULL);
}

4) If the timer was initially armed with a former expiration value
before this call to timer_settime() and the current call sets an
early deadline that has already expired, the timer fires inline
within posix_cpu_timer_set(). In this case it must have been dequeued
before firing inline with its new expiration value, yet it hasn't
been disarmed in this case. So the process wide cputime counter and
the tick dependency may still be around for a while even after the
timer fired.

The following code snippet can reproduce this:

void trigger_process_counter(void)
{
timer_t id;
struct itimerspec val = { };

signal(SIGALRM, SIG_IGN);
timer_create(CLOCK_PROCESS_CPUTIME_ID, NULL, &id);
val.it_value.tv_sec = 100;
timer_settime(id, TIMER_ABSTIME, &val, NULL);
val.it_value.tv_sec = 0;
val.it_value.tv_nsec = 1;
timer_settime(id, TIMER_ABSTIME, &val, NULL);
}

Fix all these issues with triggering the related base next expiration
recalculation on the next tick. This also implies to re-evaluate the need
to keep around the process wide cputime counter and the tick dependency, in
a similar fashion to disarm_timer().

Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210726125513.271824-7-frederic@kernel.org

posix-cpu-timers: Force next_expiration recalc after timer deletion

A timer deletion only dequeues the timer but it doesn't shutdown
the related costly process wide cputimer counter and the tick dependency.

The following code snippet keeps this overhead around for one week after
the timer deletion:

void trigger_process_counter(void)
{
timer_t id;
struct itimerspec val = { };

val.it_value.tv_sec = 604800;
timer_create(CLOCK_PROCESS_CPUTIME_ID, NULL, &id);
timer_settime(id, 0, &val, NULL);
timer_delete(id);
}

Make sure the next target's tick recalculates the nearest expiration and
clears the process wide counter and tick dependency if necessary.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210726125513.271824-3-frederic@kernel.org

posix-cpu-timers: Provide mechanisms to defer timer handling to task_work

Running posix CPU timers in hard interrupt context has a few downsides:

- For PREEMPT_RT it cannot work as the expiry code needs to take
sighand lock, which is a 'sleeping spinlock' in RT. The original RT
approach of offloading the posix CPU timer handling into a high
priority thread was clumsy and provided no real benefit in general.

- For fine grained accounting it's just wrong to run this in context of
the timer interrupt because that way a process specific CPU time is
accounted to the timer interrupt.

- Long running timer interrupts caused by a large amount of expiring
timers which can be created and armed by unpriviledged user space.

There is no hard requirement to expire them in interrupt context.

If the signal is targeted at the task itself then it won't be delivered
before the task returns to user space anyway. If the signal is targeted at
a supervisor process then it might be slightly delayed, but posix CPU
timers are inaccurate anyway due to the fact that they are tied to the
tick.

Provide infrastructure to schedule task work which allows splitting the
posix CPU timer code into a quick check in interrupt context and a thread
context expiry and signal delivery function. This has to be enabled by
architectures as it requires that the architecture specific KVM
implementation handles pending task work before exiting to guest mode.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20200730102337.783470146@linutronix.de

posix-cpu-timers: Store a reference to a pid not a task

posix cpu timers do not handle the death of a process well.

This is most clearly seen when a multi-threaded process calls exec from a
thread that is not the leader of the thread group. The posix cpu timer code
continues to pin the old thread group leader and is unable to find the
siglock from there.

This results in posix_cpu_timer_del being unable to delete a timer,
posix_cpu_timer_set being unable to set a timer. Further to compensate for
the problems in posix_cpu_timer_del on a multi-threaded exec all timers
that point at the multi-threaded task are stopped.

The code for the timers fundamentally needs to check if the target
process/thread is alive. This needs an extra level of indirection. This
level of indirection is already available in struct pid.

So replace cpu.task with cpu.pid to get the needed extra layer of
indirection.

In addition to handling things more cleanly this reduces the amount of
memory a timer can pin when a process exits and then is reaped from
a task_struct to the vastly smaller struct pid.

Fixes: e0a70217107e ("posix-cpu-timers: workaround to suppress the problems with mt exec")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/87wo86tz6d.fsf@x220.int.ebiederm.org

posix-cpu-timers: Always clear head pointer on dequeue

The head pointer in struct cpu_timer is checked to be NULL in
posix_cpu_timer_del() when the delete raced with the exit cleanup. The
works correctly as long as the timer is actually dequeued via
posix_cpu_timers_exit*().

But if the timer was dequeued due to expiry the head pointer is still set
and triggers the warning.

In fact keeping the head pointer around after any dequeue is pointless as
is has no meaning at all after that.

Clear the head pointer always on dequeue and remove the unused requeue
function while at it.

Fixes: 60bda037f1dd ("posix-cpu-timers: Utilize timerqueue for storage")
Reported-by: syzbot+55acd54b57bb4b3840a4@syzkaller.appspotmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lkml.kernel.org/r/20190905120539.707986830@linutronix.de

posix-timers: Unbreak CONFIG_POSIX_TIMERS=n build

The rework of the posix-cpu-timers patch series dropped the empty
declaration of struct cpu_timer for the CONFIG_POSIX_TIMERS=n case which
causes the build to fail:

./include/linux/posix-timers.h:218:20: error: field 'cpu' has incomplete type

Add it back.

Fixes: 60bda037f1dd ("posix-cpu-timers: Utilize timerqueue for storage")
Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

posix-cpu-timers: Utilize timerqueue for storage

Using a linear O(N) search for timer insertion affects execution time and
D-cache footprint badly with a larger number of timers.

Switch the storage to a timerqueue which is already used for hrtimers and
alarmtimers. It does not affect the size of struct k_itimer as it.alarm is
still larger.

The extra list head for the expiry list will go away later once the expiry
is moved into task work context.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1908272129220.1939@nanos.tec.linutronix.de

posix-cpu-timers: Move state tracking to struct posix_cputimers

Put it where it belongs and clean up the ifdeffery in fork completely.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190821192922.743229404@linutronix.de

posix-cpu-timers: Get rid of zero checks

Deactivation of the expiry cache is done by setting all clock caches to
0. That requires to have a check for zero in all places which update the
expiry cache:

if (cache == 0 || new < cache)
cache = new;

Use U64_MAX as the deactivated value, which allows to remove the zero
checks when updating the cache and reduces it to the obvious check:

if (new < cache)
cache = new;

This also removes the weird workaround in do_prlimit() which was required
to convert a RLIMIT_CPU value of 0 (immediate expiry) to 1 because handing
in 0 to the posix CPU timer code would have effectively disarmed it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lkml.kernel.org/r/20190821192922.275086128@linutronix.de

posix-cpu-timers: Restructure expiry array

Now that the abused struct task_cputime is gone, it's more natural to
bundle the expiry cache and the list head of each clock into a struct and
have an array of those structs.

Follow the hrtimer naming convention of 'bases' and rename the expiry cache
to 'nextevt' and adapt all usage sites.

Generates also better code .text size shrinks by 80 bytes.

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1908262021140.1939@nanos.tec.linutronix.de

posix-cpu-timers: Remove cputime_expires

The last users of the magic struct cputime based expiry cache are
gone. Remove the leftovers.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lkml.kernel.org/r/20190821192921.790209622@linutronix.de

posix-cpu-timers: Remove the odd field rename defines

The last users of the odd define based renaming of struct task_cputime
members are gone. Good riddance.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lkml.kernel.org/r/20190821192921.499058279@linutronix.de

posix-cpu-timers: Provide array based access to expiry cache

Using struct task_cputime for the expiry cache is a pretty odd choice and
comes with magic defines to rename the fields for usage in the expiry
cache.

struct task_cputime is basically a u64 array with 3 members, but it has
distinct members.

The expiry cache content is different than the content of task_cputime
because

expiry[PROF] = task_cputime.stime + task_cputime.utime
expiry[VIRT] = task_cputime.utime
expiry[SCHED] = task_cputime.sum_exec_runtime

So there is no direct mapping between task_cputime and the expiry cache and
the #define based remapping is just a horrible hack.

Having the expiry cache array based allows further simplification of the
expiry code.

To avoid an all in one cleanup which is hard to review add a temporary
anonymous union into struct task_cputime which allows array based access to
it. That requires to reorder the members. Add a build time sanity check to
validate that the members are at the same place.

The union and the build time checks will be removed after conversion.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lkml.kernel.org/r/20190821192921.105793824@linutronix.de

posix-cpu-timers: Move expiry cache into struct posix_cputimers

The expiry cache belongs into the posix_cputimers container where the other
cpu timers information is.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lkml.kernel.org/r/20190821192921.014444012@linutronix.de

posix-cpu-timers: Create a container struct

Per task/process data of posix CPU timers is all over the place which
makes the code hard to follow and requires ifdeffery.

Create a container to hold all this information in one place, so data is
consolidated and the ifdeffery can be confined to the posix timer header
file and removed from places like fork.

As a first step, move the cpu_timers list head array into the new struct
and clean up the initializers and simplify fork. The remaining #ifdef in
fork will be removed later.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lkml.kernel.org/r/20190821192920.819418976@linutronix.de

posix-cpu-timers: Remove tsk argument from run_posix_cpu_timers()

It's always current. Don't give people wrong ideas.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lkml.kernel.org/r/20190819143801.945469967@linutronix.de

posix-timers: Cleanup forward declarations and includes

- Rename struct siginfo to kernel_siginfo as that is used and required
- Add a forward declaration for task_struct and remove sched.h include
- Remove timex.h include as it is not needed

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lkml.kernel.org/r/20190819143801.472005793@linutronix.de

posix-timers: Move rcu_head out of it union

Timer deletion on PREEMPT_RT is prone to priority inversion and live
locks. The hrtimer code has a synchronization mechanism for this. Posix CPU
timers will grow one.

But that mechanism cannot be invoked while holding the k_itimer lock
because that can deadlock against the running timer callback. So the lock
must be dropped which allows the timer to be freed.

The timer free can be prevented by taking RCU readlock before dropping the
lock, but because the rcu_head is part of the 'it' union a concurrent free
will overwrite the hrtimer on which the task is trying to synchronize.

Move the rcu_head out of the union to prevent this.

[ tglx: Fixed up kernel-doc. Rewrote changelog ]

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20190730223828.965541887@linutronix.de

posix-cpu-timers: Remove private interval storage

Posix CPU timers store the interval in private storage for historical
reasons (it_interval used to be a non scalar representation on 32bit
systems). This is gone and there is no reason for duplicated storage
anymore.

Use it_interval everywhere.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "H.J. Lu" <hjl.tools@gmail.com>
Link: https://lkml.kernel.org/r/20190111133500.945255655@linutronix.de

signal: Distinguish between kernel_siginfo and siginfo

Linus recently observed that if we did not worry about the padding
member in struct siginfo it is only about 48 bytes, and 48 bytes is
much nicer than 128 bytes for allocating on the stack and copying
around in the kernel.

The obvious thing of only adding the padding when userspace is
including siginfo.h won't work as there are sigframe definitions in
the kernel that embed struct siginfo.

So split siginfo in two; kernel_siginfo and siginfo. Keeping the
traditional name for the userspace definition. While the version that
is used internally to the kernel and ultimately will not be padded to
128 bytes is called kernel_siginfo.

The definition of struct kernel_siginfo I have put in include/signal_types.h

A set of buildtime checks has been added to verify the two structures have
the same field offsets.

To make it easy to verify the change kernel_siginfo retains the same
size as siginfo. The reduction in size comes in a following change.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

posix-timers: Sanitize overrun handling

The posix timer overrun handling is broken because the forwarding functions
can return a huge number of overruns which does not fit in an int. As a
consequence timer_getoverrun(2) and siginfo::si_overrun can turn into
random number generators.

The k_clock::timer_forward() callbacks return a 64 bit value now. Make
k_itimer::ti_overrun[_last] 64bit as well, so the kernel internal
accounting is correct. 3Remove the temporary (int) casts.

Add a helper function which clamps the overrun value returned to user space
via timer_getoverrun(2) or siginfo::si_overrun limited to a positive value
between 0 and INT_MAX. INT_MAX is an indicator for user space that the
overrun value has been clamped.

Reported-by: Team OWL337 <icytxw@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Link: https://lkml.kernel.org/r/20180626132705.018623573@linutronix.de

posix-timers: Prevent UB from shifting negative signed value

Shifting a negative signed number is undefined behavior. Looking at the
macros MAKE_PROCESS_CPUCLOCK and FD_TO_CLOCKID, it seems that the
subexpression:

(~(clockid_t) (pid) << 3)

where clockid_t resolves to a signed int, which once negated, is
undefined behavior to shift the value of if the results thus far are
negative.

It was further suggested to make these macros into inline functions.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Nick Desaulniers <nick.desaulniers@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Dimitri Sivanich <sivanich@hpe.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-kselftest@vger.kernel.org
Cc: Shuah Khan <shuah@kernel.org>
Cc: Deepa Dinamani <deepa.kernel@gmail.com>
Link: https://lkml.kernel.org/r/1514517100-18051-1-git-send-email-nick.desaulniers@gmail.com

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.

For non */uapi/* files that summary was:

SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139

and resulted in the first patch in this series.

If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:

SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930

and resulted in the second patch in this series.

- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:

SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1

and that resulted in the third patch in this series.

- when the two scanners agreed on the detected license(s), that became
the concluded license(s).

- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.

- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).

- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.

- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct

This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.

Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

time: introduce {get,put}_itimerspec64

As we change the user space type for the timerfd and posix timer
functions to newer data types, we need some form of conversion
helpers to avoid duplicating that logic.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

time/posix-timers: Move the compat copyouts to the nanosleep implementations

Turn restart_block.nanosleep.{rmtp,compat_rmtp} into a tagged union (kind =
1 -> native, kind = 2 -> compat, kind = 0 -> nothing) and make the places
doing actual copyout handle compat as well as native (that will become a
helper in the next commit). Result: compat wrappers, messing with
reassignments, etc. are gone.

[ tglx: Folded in a variant of Peter Zijlstras enum patch ]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170607084241.28657-6-viro@ZenIV.linux.org.uk

posix-timers: Add active flag to k_itimer

Keep track of the activation state of posix timers. This is a preparatory
change for making common_timer_get() usable by both hrtimer and alarm timer
implementations.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/20170530211656.967783982@linutronix.de

posix-timers: Rename do_schedule_next_timer

That function is a misnomer. Rename it with a proper prefix to
posixtimer_rearm().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/20170530211656.811362578@linutronix.de

posix-timers: Store k_clock pointer in k_itimer

Having the k_clock pointer in the k_itimer struct avoids the lookup in
several code pathes and makes the next steps of unification of the hrtimer
and alarmtimer based posix timers simpler.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/20170530211656.641222072@linutronix.de

posix-timers: Move interval out of the union

Preparatory patch to unify the alarm timer and hrtimer based posix interval
timer handling.

The interval is used as a criteria for rearming decisions so moving it out
of the clock specific data structures allows later unification.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/20170530211656.563922908@linutronix.de

posix-timers: Move posix-timer internals to core

None of these declarations is required outside of kernel/time. Move them to
an internal header.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Christoph Hellwig <hch@lst.de>
Link: http://lkml.kernel.org/r/20170530211656.394803853@linutronix.de

posix-timers: Cleanup struct k_itimer

As a preparation for further changes, cleanup the formatting of the
k_itimer structure and add kernel doc comments.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/20170530211656.316574129@linutronix.de

posix-timers: Move the do_schedule_next_timer declaration

Having it in asm-generic/siginfo.h doesn't make any sense as it is in no way
architecture specific. Move it to posix-timers.h instead.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: linux-ia64@vger.kernel.org
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: sparclinux@vger.kernel.org
Cc: "David S. Miller" <davem@davemloft.net>
Link: http://lkml.kernel.org/r/20170603190102.28866-4-hch@lst.de

posix-timers: Remove mmtimer leftovers

After removing mmtimer, the mmtimer struct can be removed from the k_itimer
struct.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Russ Anderson <rja@sgi.com>
Cc: Dimitri Sivanich <sivanich@sgi.com>
Cc: Mike Travis <mike.travis@hpe.com>
Cc: Nate Zimmer <nzimmer@sgi.com>
Cc: Christoph Hellwig <hch@lst.de>
Link: http://lkml.kernel.org/r/20170526130534.GE30788@hpe.com

posix-timers: Make posix_clocks immutable

There are no more modular users providing a posix clock. The register
function is now pointless so the posix clock array can be initialized
statically at compile time and the array including the various k_clock
structs can be marked 'const'.

Inspired by changes in the Grsecurity patch set, but done proper.

[ tglx: Massaged changelog and fixed the POSIX_TIMER=n case ]

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Travis <mike.travis@hpe.com>
Cc: Dimitri Sivanich <sivanich@hpe.com>
Link: http://lkml.kernel.org/r/20170526090311.3377-3-hch@lst.de

time: Change k_clock nsleep() to use timespec64

struct timespec is not y2038 safe on 32 bit machines. Replace uses of
struct timespec with struct timespec64 in the kernel.

The syscall interfaces themselves will be changed in a separate series.

Note that the restart_block parameter for nanosleep has also been left
unchanged and will be part of syscall series noted above.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Cc: y2038@lists.linaro.org
Cc: john.stultz@linaro.org
Cc: arnd@arndb.de
Link: http://lkml.kernel.org/r/1490555058-4603-8-git-send-email-deepa.kernel@gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

time: Change k_clock timer_set() and timer_get() to use timespec64

struct timespec is not y2038 safe on 32 bit machines. Replace uses of
struct timespec with struct timespec64 in the kernel.

struct itimerspec internally uses struct timespec. Use struct itimerspec64
which uses struct timespec64.

The syscall interfaces themselves will be changed in a separate series.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Cc: y2038@lists.linaro.org
Cc: john.stultz@linaro.org
Cc: arnd@arndb.de
Link: http://lkml.kernel.org/r/1490555058-4603-7-git-send-email-deepa.kernel@gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

time: Change k_clock clock_set() to use timespec64

struct timespec is not y2038 safe on 32 bit machines. Replace uses of
struct timespec with struct timespec64 in the kernel.

The syscall interfaces themselves will be changed in a separate series.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Cc: y2038@lists.linaro.org
Cc: john.stultz@linaro.org
Cc: arnd@arndb.de
Link: http://lkml.kernel.org/r/1490555058-4603-6-git-send-email-deepa.kernel@gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

time: Change k_clock clock_getres() to use timespec64

struct timespec is not y2038 safe on 32 bit machines. Replace uses of
struct timespec with struct timespec64 in the kernel. The syscall
interfaces themselves will be changed in a separate series.

The clock_getres() interface has also been changed to use timespec64 even
though this particular interface is not affected by the y2038 problem. This
helps verification for internal kernel code for y2038 readiness by getting
rid of time_t/ timeval/ timespec completely.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Cc: y2038@lists.linaro.org
Cc: john.stultz@linaro.org
Cc: arnd@arndb.de
Link: http://lkml.kernel.org/r/1490555058-4603-5-git-send-email-deepa.kernel@gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

time: Change k_clock clock_get() to use timespec64

struct timespec is not y2038 safe on 32 bit machines. Replace uses of
struct timespec with struct timespec64 in the kernel.

The syscall interfaces themselves will be changed in a separate series.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Cc: y2038@lists.linaro.org
Cc: john.stultz@linaro.org
Cc: arnd@arndb.de
Link: http://lkml.kernel.org/r/1490555058-4603-4-git-send-email-deepa.kernel@gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

timers/itimer: Convert internal cputime_t units to nsec

Use the new nsec based cputime accessors as part of the whole cputime
conversion from cputime_t to nsecs.

Also convert itimers to use nsec based internal counters. This simplifies
it and removes the whole game with error/inc_error which served to deal
with cputime_t random granularity.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Link: http://lkml.kernel.org/r/1485832191-26889-20-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

timers/posix-timers: Convert internals to use nsecs

Use the new nsec based cputime accessors as part of the whole cputime
conversion from cputime_t to nsecs.

Also convert posix-cpu-timers to use nsec based internal counters to
simplify it.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Link: http://lkml.kernel.org/r/1485832191-26889-19-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

posix-cpu-timers: Migrate to use new tick dependency mask model

Instead of providing asynchronous checks for the nohz subsystem to verify
posix cpu timers tick dependency, migrate the latter to the new mask.

In order to keep track of the running timers and expose the tick
dependency accordingly, we must probe the timers queuing and dequeuing
on threads and process lists.

Unfortunately it implies both task and signal level dependencies. We
should be able to further optimize this and merge all that on the task
level dependency, at the cost of a bit of complexity and may be overhead.

Reviewed-by: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

posix_cpu_timer: consolidate expiry time type

The posix cpu timer expiry time is stored in a union of two types: a 64
bits field if we rely on scheduler precise accounting, or a cputime_t if
we rely on jiffies.

This results in quite some duplicate code and special cases to handle the
two types.

Just unify this into a single 64 bits field. cputime_t can always fit
into it.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Olivier Langlois <olivier@trillion01.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

posix_timers: New API to prevent from stopping the tick when timers are running

Bring a new helper that the full dynticks infrastructure can
call in order to know if it can safely stop the tick from
the posix cpu timers subsystem point of view.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.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: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.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>

posix timers: Allocate timer id per process (v2)

Currently kernel generates IDs for posix timers in a global manner --
there's a kernel-wide IDR tree from which IDs are created. This makes
it impossible to recreate a timer with a desired ID (in particular
this is done by the CRIU checkpoint-restore project) -- since these
IDs are global it may happen, that at the time we recreate a timer, the
ID we want for it is already busy by some other timer.

In order to address this, replace the IDR tree with a global hash
table for timers and makes timer IDs unique per signal_struct (to
which timers are linked anyway). With this, two timers belonging to
different processes may have equal IDs and we can recreate either of
them with the ID we want.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Matthew Helsley <matt.helsley@gmail.com>
Link: http://lkml.kernel.org/r/513D9FF5.9010004@parallels.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

alarmtimers: Remove period from alarm structure

Now that periodic alarmtimers are managed by the handler function,
remove the period value from the alarm structure and let the handlers
manage the interval on their own.

CC: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>

posix-timers: RCU conversion

Ben Nagy reported a scalability problem with KVM/QEMU that hit very hard
a single spinlock (idr_lock) in posix-timers code, on its 48 core
machine.

Even on a 16 cpu machine (2x4x2), a single test can show 98% of cpu time
used in ticket_spin_lock, from lock_timer

Ref: http://www.spinics.net/lists/kvm/msg51526.html

Switching to RCU is quite easy, IDR being already RCU ready. idr_lock
should be locked only for an insert/delete, not a lookup.

Benchmark on a 2x4x2 machine, 16 processes calling timer_gettime().

Before :

real 1m18.669s
user 0m1.346s
sys 1m17.180s

After :

real 0m3.296s
user 0m1.366s
sys 0m1.926s

Reported-by: Ben Nagy <ben@iagu.net>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Tested-by: Ben Nagy <ben@iagu.net>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: John Stultz <johnstul@us.ibm.com>
Cc: Richard Cochran <richard.cochran@omicron.at>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

timers: Posix interface for alarm-timers

This patch exposes alarm-timers to userland via the posix clock
and timers interface, using two new clockids: CLOCK_REALTIME_ALARM
and CLOCK_BOOTTIME_ALARM. Both clockids behave identically to
CLOCK_REALTIME and CLOCK_BOOTTIME, respectively, but timers
set against the _ALARM suffixed clockids will wake the system if
it is suspended.

Some background can be found here:
https://lwn.net/Articles/429925/

The concept for Alarm-timers was inspired by the Android Alarm
driver (by Arve Hjønnevåg) found in the Android kernel tree.

See: http://android.git.kernel.org/?p=kernel/common.git;a=blob;f=drivers/rtc/alarm.c;h=1250edfbdf3302f5e4ea6194847c6ef4bb7beb1c;hb=android-2.6.36

While the in-kernel interface is pretty similar between
alarm-timers and Android alarm driver, the user-space interface
for the Android alarm driver is via ioctls to a new char device.
As mentioned above, I've instead chosen to export this functionality
via the posix interface, as it seemed a little simpler and avoids
creating duplicate interfaces to things like CLOCK_REALTIME and
CLOCK_MONOTONIC under alternate names (ie:ANDROID_ALARM_RTC and
ANDROID_ALARM_SYSTEMTIME).

The semantics of the Android alarm driver are different from what
this posix interface provides. For instance, threads other then
the thread waiting on the Android alarm driver are able to modify
the alarm being waited on. Also this interface does not allow
the same wakelock semantics that the Android driver provides
(ie: kernel takes a wakelock on RTC alarm-interupt, and holds it
through process wakeup, and while the process runs, until the
process either closes the char device or calls back in to wait
on a new alarm).

One potential way to implement similar semantics may be via
the timerfd infrastructure, but this needs more research.

There may also need to be some sort of sysfs system level policy
hooks that allow alarm timers to be disabled to keep them
from firing at inappropriate times (ie: laptop in a well insulated
bag, mid-flight).

CC: Arve Hjønnevåg <arve@android.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Alessandro Zummo <a.zummo@towertech.it>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>

posix clocks: Introduce dynamic clocks

This patch adds support for adding and removing posix clocks. The
clock lifetime cycle is patterned after usb devices. Each clock is
represented by a standard character device. In addition, the driver
may optionally implement custom character device operations.

The posix clock and timer system calls listed below now work with
dynamic posix clocks, as well as the traditional static clocks.
The following system calls are affected:

- clock_adjtime (brand new syscall)
- clock_gettime
- clock_getres
- clock_settime
- timer_create
- timer_delete
- timer_gettime
- timer_settime

[ tglx: Adapted to the posix-timer cleanup. Moved clock_posix_dynamic
to posix-clock.c and made all referenced functions static ]

Signed-off-by: Richard Cochran <richard.cochran@omicron.at>
Acked-by: John Stultz <johnstul@us.ibm.com>
LKML-Reference: <20110201134420.164172635@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

posix-timers: Cleanup namespace

Rename register_posix_clock() to posix_timers_register_clock(). That's
what the function really does. As a side effect this cleans up the
posix_clock namespace for the upcoming dynamic posix_clock
infrastructure.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Richard Cochran <richard.cochran@omicron.at>
Cc: John Stultz <johnstul@us.ibm.com>
LKML-Reference: <alpine.LFD.2.00.1102021222240.31804@localhost6.localdomain6>

posix-timers: Add support for fd based clocks

Extend the negative clockids which are currently used by posix cpu
timers to encode the PID with a file descriptor based type which
encodes the fd in the upper bits.

Originally-from: Richard Cochran <richard.cochran@omicron.at>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <johnstul@us.ibm.com>
LKML-Reference: <20110201134420.062860200@linutronix.de>

posix-timers: Introduce a syscall for clock tuning.

A new syscall is introduced that allows tuning of a POSIX clock. The
new call, clock_adjtime, takes two parameters, the clock ID and a
pointer to a struct timex. Any ADJTIMEX(2) operation may be requested
via this system call, but various POSIX clocks may or may not support
tuning.

[ tglx: Adapted to the posix-timer cleanup series. Avoid copy_to_user
in the error case ]

Signed-off-by: Richard Cochran <richard.cochran@omicron.at>
Acked-by: John Stultz <johnstul@us.ibm.com>
LKML-Reference: <20110201134419.869804645@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

posix-timers: Make posix-cpu-timers functions static

All functions are accessed via clock_posix_cpu now. So make them static.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <johnstul@us.ibm.com>
Tested-by: Richard Cochran <richard.cochran@omicron.at>
LKML-Reference: <20110201134419.389755466@linutronix.de>

posix-timers: Remove useless res field from k_clock

The res member of kclock is only used by mmtimer.c, but even there it
contains redundant information. Remove the field and fixup mmtimer.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <johnstul@us.ibm.com>
Tested-by: Richard Cochran <richard.cochran@omicron.at>
LKML-Reference: <20110201134418.808714587@linutronix.de>

posix-timers: Convert clock_settime to clockid_to_kclock()

Use the new kclock decoding function in clock_settime and cleanup all
kclocks which use the default functions. Rename the misnomed
common_clock_set() to posix_clock_realtime_set().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <johnstul@us.ibm.com>
Tested-by: Richard Cochran <richard.cochran@omicron.at>
LKML-Reference: <20110201134418.518851246@linutronix.de>

posix-timers: Convert clock_nanosleep to clockid_to_kclock()

Use the new kclock decoding function in clock_nanosleep and cleanup all
kclocks which use the default functions.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <johnstul@us.ibm.com>
Tested-by: Richard Cochran <richard.cochran@omicron.at>
LKML-Reference: <20110201134418.034175556@linutronix.de>

posix-timers: Introduce clock_posix_cpu

The CLOCK_DISPATCH() macro is a horrible magic. We call common
functions if a function pointer is not set. That's just backwards.

To support dynamic file decriptor based clocks we need to cleanup that
dispatch logic.

Create a k_clock struct clock_posix_cpu which has all the
posix-cpu-timer functions filled in. After the cleanup the functions
can be made static.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <johnstul@us.ibm.com>
Tested-by: Richard Cochran <richard.cochran@omicron.at>
LKML-Reference: <20110201134417.841974553@linutronix.de>

time: Correct the *settime* parameters

Both settimeofday() and clock_settime() promise with a 'const'
attribute not to alter the arguments passed in. This patch adds the
missing 'const' attribute into the various kernel functions
implementing these calls.

Signed-off-by: Richard Cochran <richard.cochran@omicron.at>
Acked-by: John Stultz <johnstul@us.ibm.com>
LKML-Reference: <20110201134417.545698637@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

rlimits: add task_struct to update_rlimit_cpu

Add task_struct as a parameter to update_rlimit_cpu to be able to set
rlimit_cpu of different task than current.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Acked-by: James Morris <jmorris@namei.org>

posix-timers: use "struct pid*" instead of "struct task_struct*"

Impact: restructure, clean up code

k_itimer holds the ref to the ->it_process until sys_timer_delete(). This
allows to pin up to RLIMIT_SIGPENDING dead task_struct's. Change the code
to use "struct pid *" instead.

The patch doesn't kill ->it_process, it places ->it_pid into the union.
->it_process is still used by do_cpu_nanosleep() as before. It would be
trivial to change the nanosleep code as well, but since it uses it_process
in a special way I think it is better to keep this field for grep.

The patch bloats the kernel by 104 bytes and it also adds the new pointer,
->it_signal, to k_itimer. It is used by lock_timer() to verify that the
found timer was not created by another process. It is not clear why do we
use the global database (and thus the global idr_lock) for posix timers.
We still need the signal_struct->posix_timers which contains all useable
timers, perhaps it is better to use some form of per-process array
instead.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

posix-timers: kill ->it_sigev_signo and ->it_sigev_value

With the recent changes ->it_sigev_signo and ->it_sigev_value are only
used in sys_timer_create(), kill them.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: mingo@elte.hu
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

timers: fix itimer/many thread hang

Overview

This patch reworks the handling of POSIX CPU timers, including the
ITIMER_PROF, ITIMER_VIRT timers and rlimit handling. It was put together
with the help of Roland McGrath, the owner and original writer of this code.

The problem we ran into, and the reason for this rework, has to do with using
a profiling timer in a process with a large number of threads. It appears
that the performance of the old implementation of run_posix_cpu_timers() was
at least O(n*3) (where "n" is the number of threads in a process) or worse.
Everything is fine with an increasing number of threads until the time taken
for that routine to run becomes the same as or greater than the tick time, at
which point things degrade rather quickly.

This patch fixes bug 9906, "Weird hang with NPTL and SIGPROF."

Code Changes

This rework corrects the implementation of run_posix_cpu_timers() to make it
run in constant time for a particular machine. (Performance may vary between
one machine and another depending upon whether the kernel is built as single-
or multiprocessor and, in the latter case, depending upon the number of
running processors.) To do this, at each tick we now update fields in
signal_struct as well as task_struct. The run_posix_cpu_timers() function
uses those fields to make its decisions.

We define a new structure, "task_cputime," to contain user, system and
scheduler times and use these in appropriate places:

struct task_cputime {
cputime_t utime;
cputime_t stime;
unsigned long long sum_exec_runtime;
};

This is included in the structure "thread_group_cputime," which is a new
substructure of signal_struct and which varies for uniprocessor versus
multiprocessor kernels. For uniprocessor kernels, it uses "task_cputime" as
a simple substructure, while for multiprocessor kernels it is a pointer:

struct thread_group_cputime {
struct task_cputime totals;
};

struct thread_group_cputime {
struct task_cputime *totals;
};

We also add a new task_cputime substructure directly to signal_struct, to
cache the earliest expiration of process-wide timers, and task_cputime also
replaces the it_*_expires fields of task_struct (used for earliest expiration
of thread timers). The "thread_group_cputime" structure contains process-wide
timers that are updated via account_user_time() and friends. In the non-SMP
case the structure is a simple aggregator; unfortunately in the SMP case that
simplicity was not achievable due to cache-line contention between CPUs (in
one measured case performance was actually _worse_ on a 16-cpu system than
the same test on a 4-cpu system, due to this contention). For SMP, the
thread_group_cputime counters are maintained as a per-cpu structure allocated
using alloc_percpu(). The timer functions update only the timer field in
the structure corresponding to the running CPU, obtained using per_cpu_ptr().

We define a set of inline functions in sched.h that we use to maintain the
thread_group_cputime structure and hide the differences between UP and SMP
implementations from the rest of the kernel. The thread_group_cputime_init()
function initializes the thread_group_cputime structure for the given task.
The thread_group_cputime_alloc() is a no-op for UP; for SMP it calls the
out-of-line function thread_group_cputime_alloc_smp() to allocate and fill
in the per-cpu structures and fields. The thread_group_cputime_free()
function, also a no-op for UP, in SMP frees the per-cpu structures. The
thread_group_cputime_clone_thread() function (also a UP no-op) for SMP calls
thread_group_cputime_alloc() if the per-cpu structures haven't yet been
allocated. The thread_group_cputime() function fills the task_cputime
structure it is passed with the contents of the thread_group_cputime fields;
in UP it's that simple but in SMP it must also safely check that tsk->signal
is non-NULL (if it is it just uses the appropriate fields of task_struct) and,
if so, sums the per-cpu values for each online CPU. Finally, the three
functions account_group_user_time(), account_group_system_time() and
account_group_exec_runtime() are used by timer functions to update the
respective fields of the thread_group_cputime structure.

Non-SMP operation is trivial and will not be mentioned further.

The per-cpu structure is always allocated when a task creates its first new
thread, via a call to thread_group_cputime_clone_thread() from copy_signal().
It is freed at process exit via a call to thread_group_cputime_free() from
cleanup_signal().

All functions that formerly summed utime/stime/sum_sched_runtime values from
from all threads in the thread group now use thread_group_cputime() to
snapshot the values in the thread_group_cputime structure or the values in
the task structure itself if the per-cpu structure hasn't been allocated.

Finally, the code in kernel/posix-cpu-timers.c has changed quite a bit.
The run_posix_cpu_timers() function has been split into a fast path and a
slow path; the former safely checks whether there are any expired thread
timers and, if not, just returns, while the slow path does the heavy lifting.
With the dedicated thread group fields, timers are no longer "rebalanced" and
the process_timer_rebalance() function and related code has gone away. All
summing loops are gone and all code that used them now uses the
thread_group_cputime() inline. When process-wide timers are set, the new
task_cputime structure in signal_struct is used to cache the earliest
expiration; this is checked in the fast path.

Performance

The fix appears not to add significant overhead to existing operations. It
generally performs the same as the current code except in two cases, one in
which it performs slightly worse (Case 5 below) and one in which it performs
very significantly better (Case 2 below). Overall it's a wash except in those
two cases.

I've since done somewhat more involved testing on a dual-core Opteron system.

Case 1: With no itimer running, for a test with 100,000 threads, the fixed
kernel took 1428.5 seconds, 513 seconds more than the unfixed system,
all of which was spent in the system. There were twice as many
voluntary context switches with the fix as without it.

Case 2: With an itimer running at .01 second ticks and 4000 threads (the most
an unmodified kernel can handle), the fixed kernel ran the test in
eight percent of the time (5.8 seconds as opposed to 70 seconds) and
had better tick accuracy (.012 seconds per tick as opposed to .023
seconds per tick).

Case 3: A 4000-thread test with an initial timer tick of .01 second and an
interval of 10,000 seconds (i.e. a timer that ticks only once) had
very nearly the same performance in both cases: 6.3 seconds elapsed
for the fixed kernel versus 5.5 seconds for the unfixed kernel.

With fewer threads (eight in these tests), the Case 1 test ran in essentially
the same time on both the modified and unmodified kernels (5.2 seconds versus
5.8 seconds). The Case 2 test ran in about the same time as well, 5.9 seconds
versus 5.4 seconds but again with much better tick accuracy, .013 seconds per
tick versus .025 seconds per tick for the unmodified kernel.

Since the fix affected the rlimit code, I also tested soft and hard CPU limits.

Case 4: With a hard CPU limit of 20 seconds and eight threads (and an itimer
running), the modified kernel was very slightly favored in that while
it killed the process in 19.997 seconds of CPU time (5.002 seconds of
wall time), only .003 seconds of that was system time, the rest was
user time. The unmodified kernel killed the process in 20.001 seconds
of CPU (5.014 seconds of wall time) of which .016 seconds was system
time. Really, though, the results were too close to call. The results
were essentially the same with no itimer running.

Case 5: With a soft limit of 20 seconds and a hard limit of 2000 seconds
(where the hard limit would never be reached) and an itimer running,
the modified kernel exhibited worse tick accuracy than the unmodified
kernel: .050 seconds/tick versus .028 seconds/tick. Otherwise,
performance was almost indistinguishable. With no itimer running this
test exhibited virtually identical behavior and times in both cases.

In times past I did some limited performance testing. those results are below.

On a four-cpu Opteron system without this fix, a sixteen-thread test executed
in 3569.991 seconds, of which user was 3568.435s and system was 1.556s. On
the same system with the fix, user and elapsed time were about the same, but
system time dropped to 0.007 seconds. Performance with eight, four and one
thread were comparable. Interestingly, the timer ticks with the fix seemed
more accurate: The sixteen-thread test with the fix received 149543 ticks
for 0.024 seconds per tick, while the same test without the fix received 58720
for 0.061 seconds per tick. Both cases were configured for an interval of
0.01 seconds. Again, the other tests were comparable. Each thread in this
test computed the primes up to 25,000,000.

I also did a test with a large number of threads, 100,000 threads, which is
impossible without the fix. In this case each thread computed the primes only
up to 10,000 (to make the runtime manageable). System time dominated, at
1546.968 seconds out of a total 2176.906 seconds (giving a user time of
629.938s). It received 147651 ticks for 0.015 seconds per tick, still quite
accurate. There is obviously no comparable test without the fix.

Signed-off-by: Frank Mayhar <fmayhar@google.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

[PATCH] posix-timers: Fix clock_nanosleep() doesn't return the remaining time in compatibility mode

The clock_nanosleep() function does not return the time remaining when the
sleep is interrupted by a signal.

This patch creates a new call out, compat_clock_nanosleep_restart(), which
handles returning the remaining time after a sleep is interrupted. This
patch revives clock_nanosleep_restart(). It is now accessed via the new
call out. The compat_clock_nanosleep_restart() is used for compatibility
access.

Since this is implemented in compatibility mode the normal path is
virtually unaffected - no real performance impact.

Signed-off-by: Toyo Abe <toyoa@mvista.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] kernel/posix-timers.c: remove do_posix_clock_notimer_create()

This function is neither used nor has any real contents.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] hrtimer: convert posix timers completely

- convert posix-timers.c to use hrtimers

- remove the now obsolete abslist code

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] hrtimer: switch clock_nanosleep to hrtimer nanosleep API

Switch clock_nanosleep to use the new nanosleep functions in hrtimer.c

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] hrtimer: coding style and white space cleanup 2

style/whitespace/macro cleanups of posix-timers.h

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] hrtimer: make clockid_t arguments const

add const arguments to the posix-timers.h API functions

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Linux-2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!