linux-toradex.git/kernel/time, branch v3.10.13

timer_list: correct the iterator for timer_list

2013-09-08T05:09:58+00:00

commit 84a78a6504f5c5394a8e558702e5b54131f01d14 upstream.

Correct an issue with /proc/timer_list reported by Holger.

When reading from the proc file with a sufficiently small buffer, 2k so
not really that small, there was one could get hung trying to read the
file a chunk at a time.

The timer_list_start function failed to account for the possibility that
the offset was adjusted outside the timer_list_next.

Signed-off-by: Nathan Zimmer 
Reported-by: Holger Hans Peter Freyther 
Cc: John Stultz 
Cc: Thomas Gleixner 
Cc: Berke Durak 
Cc: Jeff Layton 
Tested-by: Al Viro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

Revert "cpuidle: Quickly notice prediction failure for repeat mode"

2013-08-12T01:35:24+00:00

commit 148519120c6d1f19ad53349683aeae9f228b0b8d upstream.

Revert commit 69a37bea (cpuidle: Quickly notice prediction failure for
repeat mode), because it has been identified as the source of a
significant performance regression in v3.8 and later as explained by
Jeremy Eder:

  We believe we've identified a particular commit to the cpuidle code
  that seems to be impacting performance of variety of workloads.
  The simplest way to reproduce is using netperf TCP_RR test, so
  we're using that, on a pair of Sandy Bridge based servers.  We also
  have data from a large database setup where performance is also
  measurably/positively impacted, though that test data isn't easily
  share-able.

  Included below are test results from 3 test kernels:

  kernel       reverts
  -----------------------------------------------------------
  1) vanilla   upstream (no reverts)

  2) perfteam2 reverts e11538d1f03914eb92af5a1a378375c05ae8520c

  3) test      reverts 69a37beabf1f0a6705c08e879bdd5d82ff6486c4
                       e11538d1f03914eb92af5a1a378375c05ae8520c

  In summary, netperf TCP_RR numbers improve by approximately 4%
  after reverting 69a37beabf1f0a6705c08e879bdd5d82ff6486c4.  When
  69a37beabf1f0a6705c08e879bdd5d82ff6486c4 is included, C0 residency
  never seems to get above 40%.  Taking that patch out gets C0 near
  100% quite often, and performance increases.

  The below data are histograms representing the %c0 residency @
  1-second sample rates (using turbostat), while under netperf test.

  - If you look at the first 4 histograms, you can see %c0 residency
    almost entirely in the 30,40% bin.
  - The last pair, which reverts 69a37beabf1f0a6705c08e879bdd5d82ff6486c4,
    shows %c0 in the 80,90,100% bins.

  Below each kernel name are netperf TCP_RR trans/s numbers for the
  particular kernel that can be disclosed publicly, comparing the 3
  test kernels.  We ran a 4th test with the vanilla kernel where
  we've also set /dev/cpu_dma_latency=0 to show overall impact
  boosting single-threaded TCP_RR performance over 11% above
  baseline.

  3.10-rc2 vanilla RX + c0 lock (/dev/cpu_dma_latency=0):
  TCP_RR trans/s 54323.78

  -----------------------------------------------------------
  3.10-rc2 vanilla RX (no reverts)
  TCP_RR trans/s 48192.47

  Receiver %c0
      0.0000 -    10.0000 [     1]: *
     10.0000 -    20.0000 [     0]:
     20.0000 -    30.0000 [     0]:
     30.0000 -    40.0000 [    59]:
  ***********************************************************
     40.0000 -    50.0000 [     1]: *
     50.0000 -    60.0000 [     0]:
     60.0000 -    70.0000 [     0]:
     70.0000 -    80.0000 [     0]:
     80.0000 -    90.0000 [     0]:
     90.0000 -   100.0000 [     0]:

  Sender %c0
      0.0000 -    10.0000 [     1]: *
     10.0000 -    20.0000 [     0]:
     20.0000 -    30.0000 [     0]:
     30.0000 -    40.0000 [    11]: ***********
     40.0000 -    50.0000 [    49]:
  *************************************************
     50.0000 -    60.0000 [     0]:
     60.0000 -    70.0000 [     0]:
     70.0000 -    80.0000 [     0]:
     80.0000 -    90.0000 [     0]:
     90.0000 -   100.0000 [     0]:

  -----------------------------------------------------------
  3.10-rc2 perfteam2 RX (reverts commit
  e11538d1f03914eb92af5a1a378375c05ae8520c)
  TCP_RR trans/s 49698.69

  Receiver %c0
      0.0000 -    10.0000 [     1]: *
     10.0000 -    20.0000 [     1]: *
     20.0000 -    30.0000 [     0]:
     30.0000 -    40.0000 [    59]:
  ***********************************************************
     40.0000 -    50.0000 [     0]:
     50.0000 -    60.0000 [     0]:
     60.0000 -    70.0000 [     0]:
     70.0000 -    80.0000 [     0]:
     80.0000 -    90.0000 [     0]:
     90.0000 -   100.0000 [     0]:

  Sender %c0
      0.0000 -    10.0000 [     1]: *
     10.0000 -    20.0000 [     0]:
     20.0000 -    30.0000 [     0]:
     30.0000 -    40.0000 [     2]: **
     40.0000 -    50.0000 [    58]:
  **********************************************************
     50.0000 -    60.0000 [     0]:
     60.0000 -    70.0000 [     0]:
     70.0000 -    80.0000 [     0]:
     80.0000 -    90.0000 [     0]:
     90.0000 -   100.0000 [     0]:

  -----------------------------------------------------------
  3.10-rc2 test RX (reverts 69a37beabf1f0a6705c08e879bdd5d82ff6486c4
  and e11538d1f03914eb92af5a1a378375c05ae8520c)
  TCP_RR trans/s 47766.95

  Receiver %c0
      0.0000 -    10.0000 [     1]: *
     10.0000 -    20.0000 [     1]: *
     20.0000 -    30.0000 [     0]:
     30.0000 -    40.0000 [    27]: ***************************
     40.0000 -    50.0000 [     2]: **
     50.0000 -    60.0000 [     0]:
     60.0000 -    70.0000 [     2]: **
     70.0000 -    80.0000 [     0]:
     80.0000 -    90.0000 [     0]:
     90.0000 -   100.0000 [    28]: ****************************

  Sender:
      0.0000 -    10.0000 [     1]: *
     10.0000 -    20.0000 [     0]:
     20.0000 -    30.0000 [     0]:
     30.0000 -    40.0000 [    11]: ***********
     40.0000 -    50.0000 [     0]:
     50.0000 -    60.0000 [     1]: *
     60.0000 -    70.0000 [     0]:
     70.0000 -    80.0000 [     3]: ***
     80.0000 -    90.0000 [     7]: *******
     90.0000 -   100.0000 [    38]: **************************************

  These results demonstrate gaining back the tendency of the CPU to
  stay in more responsive, performant C-states (and thus yield
  measurably better performance), by reverting commit
  69a37beabf1f0a6705c08e879bdd5d82ff6486c4.

Requested-by: Jeremy Eder 
Tested-by: Len Brown 
Signed-off-by: Rafael J. Wysocki 
Signed-off-by: Greg Kroah-Hartman

tick: Prevent uncontrolled switch to oneshot mode

2013-07-25T21:07:29+00:00

commit 1f73a9806bdd07a5106409bbcab3884078bd34fe upstream.

When the system switches from periodic to oneshot mode, the broadcast
logic causes a possibility that a CPU which has not yet switched to
oneshot mode puts its own clock event device into oneshot mode without
updating the state and the timer handler.

CPU0				CPU1
				per cpu tickdev is in periodic mode
				and switched to broadcast

Switch to oneshot mode
 tick_broadcast_switch_to_oneshot()
  cpumask_copy(tick_oneshot_broacast_mask,
	       tick_broadcast_mask);

  broadcast device mode = oneshot

				Timer interrupt

				irq_enter()
				 tick_check_oneshot_broadcast()
				  dev->set_mode(ONESHOT);

				tick_handle_periodic()
				 if (dev->mode == ONESHOT)
				   dev->next_event += period;
				   FAIL.

We fail, because dev->next_event contains KTIME_MAX, if the device was
in periodic mode before the uncontrolled switch to oneshot happened.

We must copy the broadcast bits over to the oneshot mask, because
otherwise a CPU which relies on the broadcast would not been woken up
anymore after the broadcast device switched to oneshot mode.

So we need to verify in tick_check_oneshot_broadcast() whether the CPU
has already switched to oneshot mode. If not, leave the device
untouched and let the CPU switch controlled into oneshot mode.

This is a long standing bug, which was never noticed, because the main
user of the broadcast x86 cannot run into that scenario, AFAICT. The
nonarchitected timer mess of ARM creates a gazillion of differently
broken abominations which trigger the shortcomings of that broadcast
code, which better had never been necessary in the first place.

Reported-and-tested-by: Stehle Vincent-B46079 
Reviewed-by: Stephen Boyd 
Cc: John Stultz ,
Cc: Mark Rutland 
Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1307012153060.4013@ionos.tec.linutronix.de
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

tick: Sanitize broadcast control logic

2013-07-25T21:07:29+00:00

commit 07bd1172902e782f288e4d44b1fde7dec0f08b6f upstream.

The recent implementation of a generic dummy timer resulted in a
different registration order of per cpu local timers which made the
broadcast control logic go belly up.

If the dummy timer is the first clock event device which is registered
for a CPU, then it is installed, the broadcast timer is initialized
and the CPU is marked as broadcast target.

If a real clock event device is installed after that, we can fail to
take the CPU out of the broadcast mask. In the worst case we end up
with two periodic timer events firing for the same CPU. One from the
per cpu hardware device and one from the broadcast.

Now the problem is that we have no way to distinguish whether the
system is in a state which makes broadcasting necessary or the
broadcast bit was set due to the nonfunctional dummy timer
installment.

To solve this we need to keep track of the system state seperately and
provide a more detailed decision logic whether we keep the CPU in
broadcast mode or not.

The old decision logic only clears the broadcast mode, if the newly
installed clock event device is not affected by power states.

The new logic clears the broadcast mode if one of the following is
true:

  - The new device is not affected by power states.

  - The system is not in a power state affected mode

  - The system has switched to oneshot mode. The oneshot broadcast is
    controlled from the deep idle state. The CPU is not in idle at
    this point, so it's safe to remove it from the mask.

If we clear the broadcast bit for the CPU when a new device is
installed, we also shutdown the broadcast device when this was the
last CPU in the broadcast mask.

If the broadcast bit is kept, then we leave the new device in shutdown
state and rely on the broadcast to deliver the timer interrupts via
the broadcast ipis.

Reported-and-tested-by: Stehle Vincent-B46079 
Reviewed-by: Stephen Boyd 
Cc: John Stultz ,
Cc: Mark Rutland 
Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1307012153060.4013@ionos.tec.linutronix.de
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

tick: Fix tick_broadcast_pending_mask not cleared

2013-06-21T11:10:34+00:00

The recent modification in the cpuidle framework consolidated the
timer broadcast code across the different drivers by setting a new
flag in the idle state. It tells the cpuidle core code to enter/exit
the broadcast mode for the cpu when entering a deep idle state. The
broadcast timer enter/exit is no longer handled by the back-end
driver.

This change made the local interrupt to be enabled *before* calling
CLOCK_EVENT_NOTIFY_EXIT.

On a tegra114, a four cores system, when the flag has been introduced
in the driver, the following warning appeared:

WARNING: at kernel/time/tick-broadcast.c:578 tick_broadcast_oneshot_control
CPU: 2 PID: 0 Comm: swapper/2 Not tainted 3.10.0-rc3-next-20130529+ #15
[] (tick_broadcast_oneshot_control+0x1a4/0x1d0) from [] (tick_notify+0x240/0x40c)
[] (tick_notify+0x240/0x40c) from [] (notifier_call_chain+0x44/0x84)
[] (notifier_call_chain+0x44/0x84) from [] (raw_notifier_call_chain+0x18/0x20)
[] (raw_notifier_call_chain+0x18/0x20) from [] (clockevents_notify+0x28/0x170)
[] (clockevents_notify+0x28/0x170) from [] (cpuidle_idle_call+0x11c/0x168)
[] (cpuidle_idle_call+0x11c/0x168) from [] (arch_cpu_idle+0x8/0x38)
[] (arch_cpu_idle+0x8/0x38) from [] (cpu_startup_entry+0x60/0x134)
[] (cpu_startup_entry+0x60/0x134) from [<804fe9a4>] (0x804fe9a4)

I don't have the hardware, so I wasn't able to reproduce the warning
but after looking a while at the code, I deduced the following:

 1. the CPU2 enters a deep idle state and sets the broadcast timer

 2. the timer expires, the tick_handle_oneshot_broadcast function is
    called, setting the tick_broadcast_pending_mask and waking up the
    idle cpu CPU2

 3. the CPU2 exits idle handles the interrupt and then invokes
    tick_broadcast_oneshot_control with CLOCK_EVENT_NOTIFY_EXIT which
    runs the following code:

    [...]
    if (dev->next_event.tv64 == KTIME_MAX)
            goto out;

    if (cpumask_test_and_clear_cpu(cpu,
                                 tick_broadcast_pending_mask))
            goto out;
    [...]

    So if there is no next event scheduled for CPU2, we fulfil the
    first condition and jump out without clearing the
    tick_broadcast_pending_mask.

 4. CPU2 goes to deep idle again and calls
    tick_broadcast_oneshot_control with CLOCK_NOTIFY_EVENT_ENTER but
    with the tick_broadcast_pending_mask set for CPU2, triggering the
    warning.

The issue only surfaced due to the modifications of the cpuidle
framework, which resulted in interrupts being enabled before the call
to the clockevents code. If the call happens before interrupts have
been enabled, the warning cannot trigger, because there is still the
event pending which caused the broadcast timer expiry.

Move the check for the next event below the check for the pending bit,
so the pending bit gets cleared whether an event is scheduled on the
cpu or not.

[ tglx: Massaged changelog ]

Signed-off-by: Daniel Lezcano 
Reported-and-tested-by: Joseph Lo 
Cc: Stephen Warren 
Cc: linux-arm-kernel@lists.infradead.org
Cc: linaro-kernel@lists.linaro.org
Link: http://lkml.kernel.org/r/1371485735-31249-1-git-send-email-daniel.lezcano@linaro.org
Signed-off-by: Thomas Gleixner

tick: Remove useless timekeeping duty attribution to broadcast source

2013-05-31T13:58:32+00:00

Since 7300711e ("clockevents: broadcast fixup possible waiters"),
the timekeeping duty is assigned to the CPU that handles the tick
broadcast clock device by the time it is set in one shot mode.

This is an issue in full dynticks mode where the timekeeping duty
must stay handled by the boot CPU for now. Otherwise it prevents
secondary CPUs from offlining and this breaks
suspend/shutdown/reboot/...

As it appears there is no reason for this timekeeping duty to be
moved to the broadcast CPU, besides nothing prevent it from being
later re-assigned to another target, let's simply remove it.

Signed-off-by: Jiri Bohac 
Reported-by: Steven Rostedt 
Acked-by: Thomas Gleixner 
Cc: Steven Rostedt 
Cc: Thomas Gleixner 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Borislav Petkov 
Signed-off-by: Frederic Weisbecker 
Signed-off-by: Ingo Molnar

nohz: Fix notifier return val that enforce timekeeping

2013-05-31T09:33:10+00:00

In tick_nohz_cpu_down_callback() if the cpu is the one handling
timekeeping, we must return something that stops the CPU_DOWN_PREPARE
notifiers and then start notify CPU_DOWN_FAILED on the already called
notifier call backs.

However traditional errno values are not handled by the notifier unless
these are encapsulated using errno_to_notifier().

Hence the current -EINVAL is misinterpreted and converted to junk after
notifier_to_errno(), leaving the notifier subsystem to random behaviour
such as eventually allowing the cpu to go down.

Fix this by using the standard NOTIFY_BAD instead.

Signed-off-by: Li Zhong 
Reviewed-by: Srivatsa S. Bhat 
Acked-by: Steven Rostedt 
Cc: Paul E. McKenney 
Cc: Ingo Molnar 
Cc: Thomas Gleixner 
Cc: Peter Zijlstra 
Cc: Borislav Petkov 
Signed-off-by: Frederic Weisbecker 
Signed-off-by: Ingo Molnar

Merge branch 'fortglx/3.10/time' of git://git.linaro.org/people/jstultz/linux into timers/urgent

2013-05-29T07:55:01+00:00

timekeeping: Correct run-time detection of persistent_clock.

2013-05-28T20:45:19+00:00

Since commit 31ade30692dc9680bfc95700d794818fa3f754ac, timekeeping_init()
checks for presence of persistent clock by attempting to read a non-zero
time value. This is an issue on platforms where persistent_clock (instead
is implemented as a free-running counter (instead of an RTC) starting
from zero on each boot and running during suspend. Examples are some ARM
platforms (e.g. PandaBoard).

An attempt to read such a clock during timekeeping_init() may return zero
value and falsely declare persistent clock as missing. Additionally, in
the above case suspend times may be accounted twice (once from
timekeeping_resume() and once from rtc_resume()), resulting in a gradual
drift of system time.

This patch does a run-time correction of the issue by doing the same check
during timekeeping_suspend().

A better long-term solution would have to return error when trying to read
non-existing clock and zero when trying to read an uninitialized clock, but
that would require changing all persistent_clock implementations.

This patch addresses the immediate breakage, for now.

Cc: John Stultz 
Cc: Thomas Gleixner 
Cc: Feng Tang 
Cc: stable@vger.kernel.org
Signed-off-by: Zoran Markovic 
[jstultz: Tweaked commit message and subject]
Signed-off-by: John Stultz

ntp: Remove unused variable flags in __hardpps

2013-05-28T20:45:19+00:00

kernel/time/ntp.c: In function ‘__hardpps’:
kernel/time/ntp.c:877: warning: unused variable ‘flags’

commit a076b2146fabb0894cae5e0189a8ba3f1502d737 ("ntp: Remove ntp_lock,
using the timekeeping locks to protect ntp state") removed its users,
but not the actual variable.

Signed-off-by: Geert Uytterhoeven 
Signed-off-by: John Stultz