From 01b4c39901e087ceebae2733857248de81476bd8 Mon Sep 17 00:00:00 2001
From: Frederic Weisbecker <frederic@kernel.org>
Date: Wed, 24 Jul 2019 15:22:59 +0200
Subject: nohz: Add TICK_DEP_BIT_RCU
If a nohz_full CPU is looping in the kernel, the scheduling-clock tick
might nevertheless remain disabled. In !PREEMPT kernels, this can
prevent RCU's attempts to enlist the aid of that CPU's executions of
cond_resched(), which can in turn result in an arbitrarily delayed grace
period and thus an OOM. RCU therefore needs a way to enable a holdout
nohz_full CPU's scheduler-clock interrupt.
This commit therefore provides a new TICK_DEP_BIT_RCU value which RCU can
pass to tick_dep_set_cpu() and friends to force on the scheduler-clock
interrupt for a specified CPU or task. In some cases, rcutorture needs
to turn on the scheduler-clock tick, so this commit also exports the
relevant symbols to GPL-licensed modules.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/time/tick-sched.c | 7 +++++++
1 file changed, 7 insertions(+)
(limited to 'kernel/time')
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 955851748dc3..d1b0a84b6112 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -198,6 +198,11 @@ static bool check_tick_dependency(atomic_t *dep)
return true;
}
+ if (val & TICK_DEP_MASK_RCU) {
+ trace_tick_stop(0, TICK_DEP_MASK_RCU);
+ return true;
+ }
+
return false;
}
@@ -324,6 +329,7 @@ void tick_nohz_dep_set_cpu(int cpu, enum tick_dep_bits bit)
preempt_enable();
}
}
+EXPORT_SYMBOL_GPL(tick_nohz_dep_set_cpu);
void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit)
{
@@ -331,6 +337,7 @@ void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit)
atomic_andnot(BIT(bit), &ts->tick_dep_mask);
}
+EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_cpu);
/*
* Set a per-task tick dependency. Posix CPU timers need this in order to elapse
--
cgit v1.2.3
From ae9e557b5be2e285f48ee945d9c8faf75d4f6a66 Mon Sep 17 00:00:00 2001
From: "Paul E. McKenney" <paulmck@kernel.org>
Date: Fri, 9 Aug 2019 16:29:42 -0700
Subject: time: Export tick start/stop functions for rcutorture
It turns out that rcutorture needs to ensure that the scheduling-clock
interrupt is enabled in CONFIG_NO_HZ_FULL kernels before starting on
CPU-bound in-kernel processing. This commit therefore exports
tick_nohz_dep_set_task(), tick_nohz_dep_clear_task(), and
tick_nohz_full_setup() to GPL kernel modules.
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/time/tick-sched.c | 4 ++++
1 file changed, 4 insertions(+)
(limited to 'kernel/time')
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index d1b0a84b6112..1ffdb4ba1ded 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -172,6 +172,7 @@ static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs)
#ifdef CONFIG_NO_HZ_FULL
cpumask_var_t tick_nohz_full_mask;
bool tick_nohz_full_running;
+EXPORT_SYMBOL_GPL(tick_nohz_full_running);
static atomic_t tick_dep_mask;
static bool check_tick_dependency(atomic_t *dep)
@@ -351,11 +352,13 @@ void tick_nohz_dep_set_task(struct task_struct *tsk, enum tick_dep_bits bit)
*/
tick_nohz_dep_set_all(&tsk->tick_dep_mask, bit);
}
+EXPORT_SYMBOL_GPL(tick_nohz_dep_set_task);
void tick_nohz_dep_clear_task(struct task_struct *tsk, enum tick_dep_bits bit)
{
atomic_andnot(BIT(bit), &tsk->tick_dep_mask);
}
+EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_task);
/*
* Set a per-taskgroup tick dependency. Posix CPU timers need this in order to elapse
@@ -404,6 +407,7 @@ void __init tick_nohz_full_setup(cpumask_var_t cpumask)
cpumask_copy(tick_nohz_full_mask, cpumask);
tick_nohz_full_running = true;
}
+EXPORT_SYMBOL_GPL(tick_nohz_full_setup);
static int tick_nohz_cpu_down(unsigned int cpu)
{
--
cgit v1.2.3