linux-kernel - [tip:sched/urgent] sched/isolation: Make CONFIG_NO_HZ_FULL select CONFIG_CPU

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Date:   Mon, 18 Dec 2017 05:21:54 -0800
From:   "tip-bot for Paul E. McKenney" <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, frederic@...nel.org,
        xiaolong.ye@...el.com, john.stultz@...aro.org, cl@...ux.com,
        lcapitulino@...hat.com, hpa@...or.com, riel@...hat.com,
        tglx@...utronix.de, cmetcalf@...lanox.com, efault@....de,
        kernellwp@...il.com, torvalds@...ux-foundation.org,
        peterz@...radead.org, mingo@...nel.org, paulmck@...ux.vnet.ibm.com
Subject: [tip:sched/urgent] sched/isolation: Make CONFIG_NO_HZ_FULL select
 CONFIG_CPU_ISOLATION

Commit-ID:  bf29cb238dc0656e6564b6a94bb82e11d2129437
Gitweb:     https://git.kernel.org/tip/bf29cb238dc0656e6564b6a94bb82e11d2129437
Author:     Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
AuthorDate: Thu, 14 Dec 2017 19:18:25 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 18 Dec 2017 13:46:42 +0100

sched/isolation: Make CONFIG_NO_HZ_FULL select CONFIG_CPU_ISOLATION

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@...el.com>
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Cc: Chris Metcalf <cmetcalf@...lanox.com>
Cc: Christoph Lameter <cl@...ux.com>
Cc: John Stultz <john.stultz@...aro.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@...hat.com>
Cc: Mike Galbraith <efault@....de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Rik van Riel <riel@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Wanpeng Li <kernellwp@...il.com>
Fixes: 5c4991e24c69 ("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@...nel.org>
---
 kernel/time/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index e776fc8..f6b5f19 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -95,6 +95,7 @@ config NO_HZ_FULL
 	select RCU_NOCB_CPU
 	select VIRT_CPU_ACCOUNTING_GEN
 	select IRQ_WORK
+	select CPU_ISOLATION
 	help
 	 Adaptively try to shutdown the tick whenever possible, even when
 	 the CPU is running tasks. Typically this requires running a single