linux.git/kernel/time/tick-broadcast.c, branch v4.19.39

tick/broadcast: Use for_each_cpu() specially on UP kernels

2018-05-15T20:45:54+00:00

for_each_cpu() unintuitively reports CPU0 as set independent of the actual
cpumask content on UP kernels. This causes an unexpected PIT interrupt
storm on a UP kernel running in an SMP virtual machine on Hyper-V, and as
a result, the virtual machine can suffer from a strange random delay of 1~20
minutes during boot-up, and sometimes it can hang forever.

Protect if by checking whether the cpumask is empty before entering the
for_each_cpu() loop.

[ tglx: Use !IS_ENABLED(CONFIG_SMP) instead of #ifdeffery ]

Signed-off-by: Dexuan Cui 
Signed-off-by: Thomas Gleixner 
Cc: Josh Poulson 
Cc: "Michael Kelley (EOSG)" 
Cc: Peter Zijlstra 
Cc: Frederic Weisbecker 
Cc: stable@vger.kernel.org
Cc: Rakib Mullick 
Cc: Jork Loeser 
Cc: Greg Kroah-Hartman 
Cc: Andrew Morton 
Cc: KY Srinivasan 
Cc: Linus Torvalds 
Cc: Alexey Dobriyan 
Cc: Dmitry Vyukov 
Link: https://lkml.kernel.org/r/KL1P15301MB000678289FE55BA365B3279ABF990@KL1P15301MB0006.APCP153.PROD.OUTLOOK.COM
Link: https://lkml.kernel.org/r/KL1P15301MB0006FA63BC22BEB64902EAA0BF930@KL1P15301MB0006.APCP153.PROD.OUTLOOK.COM

tick/broadcast: Make tick_broadcast_setup_oneshot() static

2017-06-12T16:56:01+00:00

This function isn't used outside of tick-broadcast.c, so let's
mark it static.

Signed-off-by: Stephen Boyd 
Link: http://lkml.kernel.org/r/20170608063603.13276-1-sboyd@codeaurora.org
Signed-off-by: Thomas Gleixner

Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2017-02-20T18:06:32+00:00

Pull timer updates from Thomas Gleixner:
 "Nothing exciting, just the usual pile of fixes, updates and cleanups:

   - A bunch of clocksource driver updates

   - Removal of CONFIG_TIMER_STATS and the related /proc file

   - More posix timer slim down work

   - A scalability enhancement in the tick broadcast code

   - Math cleanups"

* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (23 commits)
  hrtimer: Catch invalid clockids again
  math64, tile: Fix build failure
  clocksource/drivers/arm_arch_timer:: Mark cyclecounter __ro_after_init
  timerfd: Protect the might cancel mechanism proper
  timer_list: Remove useless cast when printing
  time: Remove CONFIG_TIMER_STATS
  clocksource/drivers/arm_arch_timer: Work around Hisilicon erratum 161010101
  clocksource/drivers/arm_arch_timer: Introduce generic errata handling infrastructure
  clocksource/drivers/arm_arch_timer: Remove fsl-a008585 parameter
  clocksource/drivers/arm_arch_timer: Add dt binding for hisilicon-161010101 erratum
  clocksource/drivers/ostm: Add renesas-ostm timer driver
  clocksource/drivers/ostm: Document renesas-ostm timer DT bindings
  clocksource/drivers/tcb_clksrc: Use 32 bit tcb as sched_clock
  clocksource/drivers/gemini: Add driver for the Cortina Gemini
  clocksource: add DT bindings for Cortina Gemini
  clockevents: Add a clkevt-of mechanism like clksrc-of
  tick/broadcast: Reduce lock cacheline contention
  timers: Omit POSIX timer stuff from task_struct when disabled
  x86/timer: Make delay() work during early bootup
  delay: Add explanation of udelay() inaccuracy
  ...

tick/broadcast: Prevent deadlock on tick_broadcast_lock

2017-02-13T08:49:31+00:00

tick_broadcast_lock is taken from interrupt context, but the following call
chain takes the lock without disabling interrupts:

[   12.703736]  _raw_spin_lock+0x3b/0x50
[   12.703738]  tick_broadcast_control+0x5a/0x1a0
[   12.703742]  intel_idle_cpu_online+0x22/0x100
[   12.703744]  cpuhp_invoke_callback+0x245/0x9d0
[   12.703752]  cpuhp_thread_fun+0x52/0x110
[   12.703754]  smpboot_thread_fn+0x276/0x320

So the following deadlock can happen:

   lock(tick_broadcast_lock);
   
      lock(tick_broadcast_lock);

intel_idle_cpu_online() is the only place which violates the calling
convention of tick_broadcast_control(). This was caused by the removal of
the smp function call in course of the cpu hotplug rework.

Instead of slapping local_irq_disable/enable() at the call site, we can
relax the calling convention and handle it in the core code, which makes
the whole machinery more robust.

Fixes: 29d7bbada98e ("intel_idle: Remove superfluous SMP fuction call")
Reported-by: Gabriel C 
Signed-off-by: Mike Galbraith 
Cc: Ruslan Ruslichenko 
Cc: Jiri Slaby 
Cc: Greg KH 
Cc: Borislav Petkov 
Cc: lwn@lwn.net
Cc: Andrew Morton 
Cc: Linus Torvalds 
Cc: Anna-Maria Gleixner 
Cc: Sebastian Siewior 
Cc: stable 
Link: http://lkml.kernel.org/r/1486953115.5912.4.camel@gmx.de
Signed-off-by: Thomas Gleixner

tick/broadcast: Reduce lock cacheline contention

2017-02-04T07:54:46+00:00

It was observed that on an Intel x86 system without the ARAT (Always
running APIC timer) feature and with fairly large number of CPUs as
well as CPUs coming in and out of intel_idle frequently, the lock
contention on the tick_broadcast_lock can become significant.

To reduce contention, the lock is put into its own cacheline and all
the cpumask_var_t variables are put into the __read_mostly section.

Running the SP benchmark of the NAS Parallel Benchmarks on a 4-socket
16-core 32-thread Nehalam system, the performance number improved
from 3353.94 Mop/s to 3469.31 Mop/s when this patch was applied on
a 4.9.6 kernel.  This is a 3.4% improvement.

Signed-off-by: Waiman Long 
Cc: "Peter Zijlstra (Intel)" 
Cc: Andrew Morton 
Link: http://lkml.kernel.org/r/1485799063-20857-1-git-send-email-longman@redhat.com
Signed-off-by: Thomas Gleixner

ktime: Get rid of the union

2016-12-25T16:21:22+00:00

ktime is a union because the initial implementation stored the time in
scalar nanoseconds on 64 bit machine and in a endianess optimized timespec
variant for 32bit machines. The Y2038 cleanup removed the timespec variant
and switched everything to scalar nanoseconds. The union remained, but
become completely pointless.

Get rid of the union and just keep ktime_t as simple typedef of type s64.

The conversion was done with coccinelle and some manual mopping up.

Signed-off-by: Thomas Gleixner 
Cc: Peter Zijlstra

tick/broadcast: Prevent NULL pointer dereference

2016-12-15T11:25:13+00:00

When a disfunctional timer, e.g. dummy timer, is installed, the tick core
tries to setup the broadcast timer.

If no broadcast device is installed, the kernel crashes with a NULL pointer
dereference in tick_broadcast_setup_oneshot() because the function has no
sanity check.

Reported-by: Mason 
Signed-off-by: Thomas Gleixner 
Cc: Mark Rutland 
Cc: Anna-Maria Gleixner 
Cc: Richard Cochran 
Cc: Sebastian Andrzej Siewior 
Cc: Daniel Lezcano 
Cc: Peter Zijlstra ,
Cc: Sebastian Frias 
Cc: Thibaud Cornic 
Cc: Robin Murphy 
Link: http://lkml.kernel.org/r/1147ef90-7877-e4d2-bb2b-5c4fa8d3144b@free.fr

tick: Move the export of tick_broadcast_oneshot_control to the proper place

2015-07-14T10:01:04+00:00

tick_broadcast_oneshot_control got moved from tick-broadcast to
tick-common, but the export stayed in the old place. Fix it up.

Fixes: f32dd1170511 'tick/broadcast: Make idle check independent from mode and config'
Reported-by: Ingo Molnar 
Signed-off-by: Thomas Gleixner

tick/broadcast: Prevent NULL pointer dereference

2015-07-11T12:26:34+00:00

Dan reported that the recent changes to the broadcast code introduced
a potential NULL dereference.

Add the proper check.

Fixes: e0454311903d "tick/broadcast: Sanity check the shutdown of the local clock_event"
Reported-by: Dan Carpenter 
Signed-off-by: Thomas Gleixner

tick/broadcast: Handle spurious interrupts gracefully

2015-07-07T16:46:48+00:00

Andriy reported that on a virtual machine the warning about negative
expiry time in the clock events programming code triggered:

hpet: hpet0 irq 40 for MSI
hpet: hpet1 irq 41 for MSI
Switching to clocksource hpet
WARNING: at kernel/time/clockevents.c:239

[] clockevents_program_event+0xdb/0xf0
[] tick_handle_periodic_broadcast+0x41/0x50
[] timer_interrupt+0x15/0x20

When the second hpet is installed as a per cpu timer the broadcast
event is not longer required and stopped, which sets the next_evt of
the broadcast device to KTIME_MAX.

If after that a spurious interrupt happens on the broadcast device,
then the current code blindly handles it and tries to reprogram the
broadcast device afterwards, which adds the period to
next_evt. KTIME_MAX + period results in a negative expiry value
causing the WARN_ON in the clockevents code to trigger.

Add a proper check for the state of the broadcast device into the
interrupt handler and return if the interrupt is spurious.

[ Folded in pointer fix from Sudeep ]

Reported-by: Andriy Gapon 
Signed-off-by: Thomas Gleixner 
Cc: Sudeep Holla 
Cc: Peter Zijlstra 
Cc: Preeti U Murthy 
Link: http://lkml.kernel.org/r/20150705205221.802094647@linutronix.de