linux-toradex.git/kernel, branch v4.9.71

sched/deadline: Use deadline instead of period when calculating overflow

2017-12-20T09:07:23+00:00

[ Upstream commit 2317d5f1c34913bac5971d93d69fb6c31bb74670 ]

I was testing Daniel's changes with his test case, and tweaked it a
little. Instead of having the runtime equal to the deadline, I
increased the deadline ten fold.

Daniel's test case had:

	attr.sched_runtime  = 2 * 1000 * 1000;		/* 2 ms */
	attr.sched_deadline = 2 * 1000 * 1000;		/* 2 ms */
	attr.sched_period   = 2 * 1000 * 1000 * 1000;	/* 2 s */

To make it more interesting, I changed it to:

	attr.sched_runtime  =  2 * 1000 * 1000;		/* 2 ms */
	attr.sched_deadline = 20 * 1000 * 1000;		/* 20 ms */
	attr.sched_period   =  2 * 1000 * 1000 * 1000;	/* 2 s */

The results were rather surprising. The behavior that Daniel's patch
was fixing came back. The task started using much more than .1% of the
CPU. More like 20%.

Looking into this I found that it was due to the dl_entity_overflow()
constantly returning true. That's because it uses the relative period
against relative runtime vs the absolute deadline against absolute
runtime.

  runtime / (deadline - t) > dl_runtime / dl_period

There's even a comment mentioning this, and saying that when relative
deadline equals relative period, that the equation is the same as using
deadline instead of period. That comment is backwards! What we really
want is:

  runtime / (deadline - t) > dl_runtime / dl_deadline

We care about if the runtime can make its deadline, not its period. And
then we can say "when the deadline equals the period, the equation is
the same as using dl_period instead of dl_deadline".

After correcting this, now when the task gets enqueued, it can throttle
correctly, and Daniel's fix to the throttling of sleeping deadline
tasks works even when the runtime and deadline are not the same.

Signed-off-by: Steven Rostedt (VMware) 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Daniel Bristot de Oliveira 
Cc: Juri Lelli 
Cc: Linus Torvalds 
Cc: Luca Abeni 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Romulo Silva de Oliveira 
Cc: Steven Rostedt 
Cc: Thomas Gleixner 
Cc: Tommaso Cucinotta 
Link: http://lkml.kernel.org/r/02135a27f1ae3fe5fd032568a5a2f370e190e8d7.1488392936.git.bristot@redhat.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

sched/deadline: Throttle a constrained deadline task activated after the deadline

2017-12-20T09:07:23+00:00

[ Upstream commit df8eac8cafce7d086be3bd5cf5a838fa37594dfb ]

During the activation, CBS checks if it can reuse the current task's
runtime and period. If the deadline of the task is in the past, CBS
cannot use the runtime, and so it replenishes the task. This rule
works fine for implicit deadline tasks (deadline == period), and the
CBS was designed for implicit deadline tasks. However, a task with
constrained deadline (deadine < period) might be awakened after the
deadline, but before the next period. In this case, replenishing the
task would allow it to run for runtime / deadline. As in this case
deadline < period, CBS enables a task to run for more than the
runtime / period. In a very loaded system, this can cause a domino
effect, making other tasks miss their deadlines.

To avoid this problem, in the activation of a constrained deadline
task after the deadline but before the next period, throttle the
task and set the replenishing timer to the begin of the next period,
unless it is boosted.

Reproducer:

 --------------- %< ---------------
  int main (int argc, char **argv)
  {
	int ret;
	int flags = 0;
	unsigned long l = 0;
	struct timespec ts;
	struct sched_attr attr;

	memset(&attr, 0, sizeof(attr));
	attr.size = sizeof(attr);

	attr.sched_policy   = SCHED_DEADLINE;
	attr.sched_runtime  = 2 * 1000 * 1000;		/* 2 ms */
	attr.sched_deadline = 2 * 1000 * 1000;		/* 2 ms */
	attr.sched_period   = 2 * 1000 * 1000 * 1000;	/* 2 s */

	ts.tv_sec = 0;
	ts.tv_nsec = 2000 * 1000;			/* 2 ms */

	ret = sched_setattr(0, &attr, flags);

	if (ret < 0) {
		perror("sched_setattr");
		exit(-1);
	}

	for(;;) {
		/* XXX: you may need to adjust the loop */
		for (l = 0; l < 150000; l++);
		/*
		 * The ideia is to go to sleep right before the deadline
		 * and then wake up before the next period to receive
		 * a new replenishment.
		 */
		nanosleep(&ts, NULL);
	}

	exit(0);
  }
  --------------- >% ---------------

On my box, this reproducer uses almost 50% of the CPU time, which is
obviously wrong for a task with 2/2000 reservation.

Signed-off-by: Daniel Bristot de Oliveira 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Juri Lelli 
Cc: Linus Torvalds 
Cc: Luca Abeni 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Romulo Silva de Oliveira 
Cc: Steven Rostedt 
Cc: Thomas Gleixner 
Cc: Tommaso Cucinotta 
Link: http://lkml.kernel.org/r/edf58354e01db46bf42df8d2dd32418833f68c89.1488392936.git.bristot@redhat.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

sched/deadline: Make sure the replenishment timer fires in the next period

2017-12-20T09:07:23+00:00

[ Upstream commit 5ac69d37784b237707a7b15d199cdb6c6fdb6780 ]

Currently, the replenishment timer is set to fire at the deadline
of a task. Although that works for implicit deadline tasks because the
deadline is equals to the begin of the next period, that is not correct
for constrained deadline tasks (deadline < period).

For instance:

f.c:
 --------------- %< ---------------
int main (void)
{
	for(;;);
}
 --------------- >% ---------------

  # gcc -o f f.c

  # trace-cmd record -e sched:sched_switch                              \
				   -e syscalls:sys_exit_sched_setattr   \
   chrt -d --sched-runtime  490000000					\
           --sched-deadline 500000000					\
	   --sched-period  1000000000 0 ./f

  # trace-cmd report | grep "{pid of ./f}"

After setting parameters, the task is replenished and continue running
until being throttled:

         f-11295 [003] 13322.113776: sys_exit_sched_setattr: 0x0

The task is throttled after running 492318 ms, as expected:

         f-11295 [003] 13322.606094: sched_switch:   f:11295 [-1] R ==> watchdog/3:32 [0]

But then, the task is replenished 500719 ms after the first
replenishment:

    -0     [003] 13322.614495: sched_switch:   swapper/3:0 [120] R ==> f:11295 [-1]

Running for 490277 ms:

         f-11295 [003] 13323.104772: sched_switch:   f:11295 [-1] R ==>  swapper/3:0 [120]

Hence, in the first period, the task runs 2 * runtime, and that is a bug.

During the first replenishment, the next deadline is set one period away.
So the runtime / period starts to be respected. However, as the second
replenishment took place in the wrong instant, the next replenishment
will also be held in a wrong instant of time. Rather than occurring in
the nth period away from the first activation, it is taking place
in the (nth period - relative deadline).

Signed-off-by: Daniel Bristot de Oliveira 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Luca Abeni 
Reviewed-by: Steven Rostedt (VMware) 
Reviewed-by: Juri Lelli 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Romulo Silva de Oliveira 
Cc: Steven Rostedt 
Cc: Thomas Gleixner 
Cc: Tommaso Cucinotta 
Link: http://lkml.kernel.org/r/ac50d89887c25285b47465638354b63362f8adff.1488392936.git.bristot@redhat.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

sched/deadline: Add missing update_rq_clock() in dl_task_timer()

2017-12-20T09:07:23+00:00

[ Upstream commit dcc3b5ffe1b32771c9a22e2c916fb94c4fcf5b79 ]

The following warning can be triggered by hot-unplugging the CPU
on which an active SCHED_DEADLINE task is running on:

 ------------[ cut here ]------------
 WARNING: CPU: 7 PID: 0 at kernel/sched/sched.h:833 replenish_dl_entity+0x71e/0xc40
 rq->clock_update_flags < RQCF_ACT_SKIP
 CPU: 7 PID: 0 Comm: swapper/7 Tainted: G    B           4.11.0-rc1+ #24
 Hardware name: LENOVO ThinkCentre M8500t-N000/SHARKBAY, BIOS FBKTC1AUS 02/16/2016
 Call Trace:
  
  dump_stack+0x85/0xc4
  __warn+0x172/0x1b0
  warn_slowpath_fmt+0xb4/0xf0
  ? __warn+0x1b0/0x1b0
  ? debug_check_no_locks_freed+0x2c0/0x2c0
  ? cpudl_set+0x3d/0x2b0
  replenish_dl_entity+0x71e/0xc40
  enqueue_task_dl+0x2ea/0x12e0
  ? dl_task_timer+0x777/0x990
  ? __hrtimer_run_queues+0x270/0xa50
  dl_task_timer+0x316/0x990
  ? enqueue_task_dl+0x12e0/0x12e0
  ? enqueue_task_dl+0x12e0/0x12e0
  __hrtimer_run_queues+0x270/0xa50
  ? hrtimer_cancel+0x20/0x20
  ? hrtimer_interrupt+0x119/0x600
  hrtimer_interrupt+0x19c/0x600
  ? trace_hardirqs_off+0xd/0x10
  local_apic_timer_interrupt+0x74/0xe0
  smp_apic_timer_interrupt+0x76/0xa0
  apic_timer_interrupt+0x93/0xa0

The DL task will be migrated to a suitable later deadline rq once the DL
timer fires and currnet rq is offline. The rq clock of the new rq should
be updated. This patch fixes it by updating the rq clock after holding
the new rq's rq lock.

Signed-off-by: Wanpeng Li 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Matt Fleming 
Cc: Juri Lelli 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1488865888-15894-1-git-send-email-wanpeng.li@hotmail.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

sched/rt: Do not pull from current CPU if only one CPU to pull

2017-12-20T09:07:17+00:00

commit f73c52a5bcd1710994e53fbccc378c42b97a06b6 upstream.

Daniel Wagner reported a crash on the BeagleBone Black SoC.

This is a single CPU architecture, and does not have a functional
arch_send_call_function_single_ipi() implementation which can crash
the kernel if that is called.

As it only has one CPU, it shouldn't be called, but if the kernel is
compiled for SMP, the push/pull RT scheduling logic now calls it for
irq_work if the one CPU is overloaded, it can use that function to call
itself and crash the kernel.

Ideally, we should disable the SCHED_FEAT(RT_PUSH_IPI) if the system
only has a single CPU. But SCHED_FEAT is a constant if sched debugging
is turned off. Another fix can also be used, and this should also help
with normal SMP machines. That is, do not initiate the pull code if
there's only one RT overloaded CPU, and that CPU happens to be the
current CPU that is scheduling in a lower priority task.

Even on a system with many CPUs, if there's many RT tasks waiting to
run on a single CPU, and that CPU schedules in another RT task of lower
priority, it will initiate the PULL logic in case there's a higher
priority RT task on another CPU that is waiting to run. But if there is
no other CPU with waiting RT tasks, it will initiate the RT pull logic
on itself (as it still has RT tasks waiting to run). This is a wasted
effort.

Not only does this help with SMP code where the current CPU is the only
one with RT overloaded tasks, it should also solve the issue that
Daniel encountered, because it will prevent the PULL logic from
executing, as there's only one CPU on the system, and the check added
here will cause it to exit the RT pull code.

Reported-by: Daniel Wagner 
Signed-off-by: Steven Rostedt (VMware) 
Acked-by: Peter Zijlstra 
Cc: Linus Torvalds 
Cc: Sebastian Andrzej Siewior 
Cc: Thomas Gleixner 
Cc: linux-rt-users 
Fixes: 4bdced5c9 ("sched/rt: Simplify the IPI based RT balancing logic")
Link: http://lkml.kernel.org/r/20171202130454.4cbbfe8d@vmware.local.home
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

tracing: Allocate mask_str buffer dynamically

2017-12-20T09:07:15+00:00

commit 90e406f96f630c07d631a021fd4af10aac913e77 upstream.

The default NR_CPUS can be very large, but actual possible nr_cpu_ids
usually is very small. For my x86 distribution, the NR_CPUS is 8192 and
nr_cpu_ids is 4. About 2 pages are wasted.

Most machines don't have so many CPUs, so define a array with NR_CPUS
just wastes memory. So let's allocate the buffer dynamically when need.

With this change, the mutext tracing_cpumask_update_lock also can be
removed now, which was used to protect mask_str.

Link: http://lkml.kernel.org/r/1512013183-19107-1-git-send-email-changbin.du@intel.com

Fixes: 36dfe9252bd4c ("ftrace: make use of tracing_cpumask")
Signed-off-by: Changbin Du 
Signed-off-by: Steven Rostedt (VMware) 
Signed-off-by: Greg Kroah-Hartman

audit: ensure that 'audit=1' actually enables audit for PID 1

2017-12-16T15:25:47+00:00

[ Upstream commit 173743dd99a49c956b124a74c8aacb0384739a4c ]

Prior to this patch we enabled audit in audit_init(), which is too
late for PID 1 as the standard initcalls are run after the PID 1 task
is forked.  This means that we never allocate an audit_context (see
audit_alloc()) for PID 1 and therefore miss a lot of audit events
generated by PID 1.

This patch enables audit as early as possible to help ensure that when
PID 1 is forked it can allocate an audit_context if required.

Reviewed-by: Richard Guy Briggs 
Signed-off-by: Paul Moore 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

jump_label: Invoke jump_label_test() via early_initcall()

2017-12-14T08:28:24+00:00

[ Upstream commit 92ee46efeb505ead3ab06d3c5ce695637ed5f152 ]

Fengguang Wu reported that running the rcuperf test during boot can cause
the jump_label_test() to hit a WARN_ON(). The issue is that the core jump
label code relies on kernel_text_address() to detect when it can no longer
update branches that may be contained in __init sections. The
kernel_text_address() in turn assumes that if the system_state variable is
greter than or equal to SYSTEM_RUNNING then __init sections are no longer
valid (since the assumption is that they have been freed). However, when
rcuperf is setup to run in early boot it can call kernel_power_off() which
sets the system_state to SYSTEM_POWER_OFF.

Since rcuperf initialization is invoked via a module_init(), we can make
the dependency of jump_label_test() needing to complete before rcuperf
explicit by calling it via early_initcall().

Reported-by: Fengguang Wu 
Signed-off-by: Jason Baron 
Acked-by: Paul E. McKenney 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Steven Rostedt 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1510609727-2238-1-git-send-email-jbaron@akamai.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

bpf: fix lockdep splat

2017-12-14T08:28:23+00:00

[ Upstream commit 89ad2fa3f043a1e8daae193bcb5fe34d5f8caf28 ]

pcpu_freelist_pop() needs the same lockdep awareness than
pcpu_freelist_populate() to avoid a false positive.

 [ INFO: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected ]

 switchto-defaul/12508 [HC0[0]:SC0[6]:HE0:SE0] is trying to acquire:
  (&htab->buckets[i].lock){......}, at: [] __htab_percpu_map_update_elem+0x1cb/0x300

 and this task is already holding:
  (dev_queue->dev->qdisc_class ?: &qdisc_tx_lock#2){+.-...}, at: [] __dev_queue_xmit+0
x868/0x1240
 which would create a new lock dependency:
  (dev_queue->dev->qdisc_class ?: &qdisc_tx_lock#2){+.-...} -> (&htab->buckets[i].lock){......}

 but this new dependency connects a SOFTIRQ-irq-safe lock:
  (dev_queue->dev->qdisc_class ?: &qdisc_tx_lock#2){+.-...}
 ... which became SOFTIRQ-irq-safe at:
   [] __lock_acquire+0x42b/0x1f10
   [] lock_acquire+0xbc/0x1b0
   [] _raw_spin_lock+0x38/0x50
   [] __dev_queue_xmit+0x868/0x1240
   [] dev_queue_xmit+0x10/0x20
   [] ip_finish_output2+0x439/0x590
   [] ip_finish_output+0x150/0x2f0
   [] ip_output+0x7d/0x260
   [] ip_local_out+0x5e/0xe0
   [] ip_queue_xmit+0x205/0x620
   [] tcp_transmit_skb+0x5a8/0xcb0
   [] tcp_write_xmit+0x242/0x1070
   [] __tcp_push_pending_frames+0x3c/0xf0
   [] tcp_rcv_established+0x312/0x700
   [] tcp_v4_do_rcv+0x11c/0x200
   [] tcp_v4_rcv+0xaa2/0xc30
   [] ip_local_deliver_finish+0xa7/0x240
   [] ip_local_deliver+0x66/0x200
   [] ip_rcv_finish+0xdd/0x560
   [] ip_rcv+0x295/0x510
   [] __netif_receive_skb_core+0x988/0x1020
   [] __netif_receive_skb+0x21/0x70
   [] process_backlog+0x6f/0x230
   [] net_rx_action+0x229/0x420
   [] __do_softirq+0xd8/0x43d
   [] do_softirq_own_stack+0x1c/0x30
   [] do_softirq+0x55/0x60
   [] __local_bh_enable_ip+0xa8/0xb0
   [] cpu_startup_entry+0x1c7/0x500
   [] start_secondary+0x113/0x140

 to a SOFTIRQ-irq-unsafe lock:
  (&head->lock){+.+...}
 ... which became SOFTIRQ-irq-unsafe at:
 ...  [] __lock_acquire+0x82f/0x1f10
   [] lock_acquire+0xbc/0x1b0
   [] _raw_spin_lock+0x38/0x50
   [] pcpu_freelist_pop+0x7a/0xb0
   [] htab_map_alloc+0x50c/0x5f0
   [] SyS_bpf+0x265/0x1200
   [] entry_SYSCALL_64_fastpath+0x12/0x17

 other info that might help us debug this:

 Chain exists of:
   dev_queue->dev->qdisc_class ?: &qdisc_tx_lock#2 --> &htab->buckets[i].lock --> &head->lock

  Possible interrupt unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(&head->lock);
                                local_irq_disable();
                                lock(dev_queue->dev->qdisc_class ?: &qdisc_tx_lock#2);
                                lock(&htab->buckets[i].lock);
   
     lock(dev_queue->dev->qdisc_class ?: &qdisc_tx_lock#2);

  *** DEADLOCK ***

Fixes: e19494edab82 ("bpf: introduce percpu_freelist")
Signed-off-by: Eric Dumazet 
Signed-off-by: David S. Miller 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

workqueue: trigger WARN if queue_delayed_work() is called with NULL @wq

2017-12-14T08:28:19+00:00

[ Upstream commit 637fdbae60d6cb9f6e963c1079d7e0445c86ff7d ]

If queue_delayed_work() gets called with NULL @wq, the kernel will
oops asynchronuosly on timer expiration which isn't too helpful in
tracking down the offender.  This actually happened with smc.

__queue_delayed_work() already does several input sanity checks
synchronously.  Add NULL @wq check.

Reported-by: Dave Jones 
Link: http://lkml.kernel.org/r/20170227171439.jshx3qplflyrgcv7@codemonkey.org.uk
Signed-off-by: Tejun Heo 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman