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CONFIG_NO_HZ_FULL doesn't make sense without CONFIG_CPU_ISOLATION. In
fact enabling the first without the second is a regression as nohz_full=
boot parameter gets silently ignored.
Besides this unnatural combination hangs RCU gp kthread when running
rcutorture for reasons that are not yet fully understood:
rcu_preempt kthread starved for 9974 jiffies! g4294967208
+c4294967207 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x402 ->cpu=0
rcu_preempt I 7464 8 2 0x80000000
Call Trace:
__schedule+0x493/0x620
schedule+0x24/0x40
schedule_timeout+0x330/0x3b0
? preempt_count_sub+0xea/0x140
? collect_expired_timers+0xb0/0xb0
rcu_gp_kthread+0x6bf/0xef0
This commit therefore makes NO_HZ_FULL select CPU_ISOLATION, which
prevents all these bad behaviours.
Reported-by: kernel test robot <xiaolong.ye@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wanpeng Li <kernellwp@gmail.com>
Fixes: 5c4991e24c ("sched/isolation: Split out new CONFIG_CPU_ISOLATION=y config from CONFIG_NO_HZ_FULL")
Link: http://lkml.kernel.org/r/1513275507-29200-2-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
145 lines
3.9 KiB
Plaintext
145 lines
3.9 KiB
Plaintext
#
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# Timer subsystem related configuration options
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#
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# Options selectable by arch Kconfig
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# Watchdog function for clocksources to detect instabilities
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config CLOCKSOURCE_WATCHDOG
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bool
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# Architecture has extra clocksource data
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config ARCH_CLOCKSOURCE_DATA
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bool
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# Clocksources require validation of the clocksource against the last
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# cycle update - x86/TSC misfeature
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config CLOCKSOURCE_VALIDATE_LAST_CYCLE
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bool
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# Timekeeping vsyscall support
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config GENERIC_TIME_VSYSCALL
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bool
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# Old style timekeeping
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config ARCH_USES_GETTIMEOFFSET
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bool
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# The generic clock events infrastructure
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config GENERIC_CLOCKEVENTS
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bool
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# Architecture can handle broadcast in a driver-agnostic way
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config ARCH_HAS_TICK_BROADCAST
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bool
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# Clockevents broadcasting infrastructure
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config GENERIC_CLOCKEVENTS_BROADCAST
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bool
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depends on GENERIC_CLOCKEVENTS
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# Automatically adjust the min. reprogramming time for
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# clock event device
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config GENERIC_CLOCKEVENTS_MIN_ADJUST
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bool
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# Generic update of CMOS clock
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config GENERIC_CMOS_UPDATE
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bool
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if GENERIC_CLOCKEVENTS
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menu "Timers subsystem"
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# Core internal switch. Selected by NO_HZ_COMMON / HIGH_RES_TIMERS. This is
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# only related to the tick functionality. Oneshot clockevent devices
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# are supported independent of this.
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config TICK_ONESHOT
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bool
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config NO_HZ_COMMON
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bool
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depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
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select TICK_ONESHOT
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choice
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prompt "Timer tick handling"
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default NO_HZ_IDLE if NO_HZ
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config HZ_PERIODIC
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bool "Periodic timer ticks (constant rate, no dynticks)"
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help
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This option keeps the tick running periodically at a constant
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rate, even when the CPU doesn't need it.
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config NO_HZ_IDLE
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bool "Idle dynticks system (tickless idle)"
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depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
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select NO_HZ_COMMON
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help
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This option enables a tickless idle system: timer interrupts
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will only trigger on an as-needed basis when the system is idle.
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This is usually interesting for energy saving.
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Most of the time you want to say Y here.
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config NO_HZ_FULL
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bool "Full dynticks system (tickless)"
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# NO_HZ_COMMON dependency
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depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
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# We need at least one periodic CPU for timekeeping
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depends on SMP
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depends on HAVE_CONTEXT_TRACKING
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# VIRT_CPU_ACCOUNTING_GEN dependency
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depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
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select NO_HZ_COMMON
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select RCU_NOCB_CPU
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select VIRT_CPU_ACCOUNTING_GEN
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select IRQ_WORK
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select CPU_ISOLATION
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help
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Adaptively try to shutdown the tick whenever possible, even when
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the CPU is running tasks. Typically this requires running a single
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task on the CPU. Chances for running tickless are maximized when
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the task mostly runs in userspace and has few kernel activity.
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You need to fill up the nohz_full boot parameter with the
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desired range of dynticks CPUs.
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This is implemented at the expense of some overhead in user <-> kernel
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transitions: syscalls, exceptions and interrupts. Even when it's
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dynamically off.
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Say N.
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endchoice
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config NO_HZ_FULL_ALL
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bool "Full dynticks system on all CPUs by default (except CPU 0)"
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depends on NO_HZ_FULL
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help
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If the user doesn't pass the nohz_full boot option to
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define the range of full dynticks CPUs, consider that all
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CPUs in the system are full dynticks by default.
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Note the boot CPU will still be kept outside the range to
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handle the timekeeping duty.
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config NO_HZ
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bool "Old Idle dynticks config"
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depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
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help
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This is the old config entry that enables dynticks idle.
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We keep it around for a little while to enforce backward
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compatibility with older config files.
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config HIGH_RES_TIMERS
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bool "High Resolution Timer Support"
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depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
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select TICK_ONESHOT
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help
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This option enables high resolution timer support. If your
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hardware is not capable then this option only increases
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the size of the kernel image.
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endmenu
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endif
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