Commit 5c4991e24c69 ("sched/isolation: Split out new
CONFIG_CPU_ISOLATION=y config from CONFIG_NO_HZ_FULL") can result in RCU
CPU stall warnings when running rcutorture with CONFIG_NO_HZ_FULL_ALL=y
and CONFIG_CPU_ISOLATION=n. These warnings are caused by RCU's
grace-period kthreads sleeping for a few jiffies, but never being
awakened:
[ 116.353432] rcu_preempt kthread starved for 9974 jiffies! g4294967208
+c4294967207 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x402 ->cpu=0
[ 116.355517] rcu_preempt I 7464 8 2 0x80000000
[ 116.356543] Call Trace:
[ 116.357008] __schedule+0x493/0x620
[ 116.357682] schedule+0x24/0x40
[ 116.358291] schedule_timeout+0x330/0x3b0
[ 116.359024] ? preempt_count_sub+0xea/0x140
[ 116.359806] ? collect_expired_timers+0xb0/0xb0
[ 116.360660] rcu_gp_kthread+0x6bf/0xef0
This commit therefore makes NO_HZ_FULL select CPU_ISOLATION, which
prevents this behavior and seems like it was the original intention in
any case.
Fixes: 5c4991e24c69 ("sched/isolation: Split out new CONFIG_CPU_ISOLATION=y
config from CONFIG_NO_HZ_FULL")
Link: https://lkml.kernel.org/r/20171126084203.GE21779@yexl-desktop
Reported-by: kernel test robot <xiaolong...@intel.com>
Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <frede...@kernel.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Chris Metcalf <cmetc...@mellanox.com>
Cc: Christoph Lameter <c...@linux.com>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Luiz Capitulino <lcapitul...@redhat.com>
Cc: Mike Galbraith <efa...@gmx.de>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Rik van Riel <r...@redhat.com>
Cc: Wanpeng Li <kernel...@gmail.com>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: John Stultz <john.stu...@linaro.org>
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
