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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2017-12-14 19:18:25 +0100
committerIngo Molnar <mingo@kernel.org>2017-12-18 13:46:42 +0100
commitbf29cb238dc0656e6564b6a94bb82e11d2129437 (patch)
tree258d36fa5a6ecf11eab88dbd1c6b7231a9087ec8 /kernel
parentLinux 4.15-rc4 (diff)
downloadlinux-bf29cb238dc0656e6564b6a94bb82e11d2129437.tar.xz
linux-bf29cb238dc0656e6564b6a94bb82e11d2129437.zip
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@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: 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@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/time/Kconfig1
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index e776fc8cc1df..f6b5f19223d6 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