[PATCH RT v3 3/5] sched: migrate_dis/enable: Use rt_invol_sleep

Scott Wood
2019-09-11T16:57:53Z

Without this, rcu_note_context_switch() will complain if an RCU read lock
is held when migrate_enable() calls stop_one_cpu(). Likewise when
migrate_disable() calls pin_current_cpu() which calls __read_rt_lock() --
which bypasses the part of the mutex code that calls rt_invol_sleep_inc().

Signed-off-by: Scott Wood <swood@redhat.com>
---
v3: Add to pin_current_cpu as well

include/linux/sched.h | 4 ++--
kernel/cpu.c | 2 ++
kernel/rcu/tree_plugin.h | 2 +-
kernel/sched/core.c | 4 ++++
4 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index edc93b74f7d8..ecf5cbb23335 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -673,7 +673,7 @@ struct task_struct {
int migrate_disable_atomic;
# endif
#endif
-#ifdef CONFIG_PREEMPT_RT_FULL
+#ifdef CONFIG_PREEMPT_RT_BASE
/* Task is blocking due to RT-specific mechanisms, not voluntarily */
int rt_invol_sleep;
#endif
@@ -1882,7 +1882,7 @@ static __always_inline bool need_resched(void)
return unlikely(tif_need_resched());
}

-#ifdef CONFIG_PREEMPT_RT_FULL
+#ifdef CONFIG_PREEMPT_RT_BASE
static inline void rt_invol_sleep_inc(void)
{
current->rt_invol_sleep++;
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 885a195dfbe0..32c6175b63b6 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -308,7 +308,9 @@ void pin_current_cpu(void)
preempt_lazy_enable();
preempt_enable();

+ rt_invol_sleep_inc();
__read_rt_lock(cpuhp_pin);
+ rt_invol_sleep_dec();

preempt_disable();
preempt_lazy_disable();
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 0da4b975cd71..6d92dafeeca5 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -292,7 +292,7 @@ void rcu_note_context_switch(bool preempt)
barrier(); /* Avoid RCU read-side critical sections leaking down. */
trace_rcu_utilization(TPS("Start context switch"));
lockdep_assert_irqs_disabled();
-#if defined(CONFIG_PREEMPT_RT_FULL)
+#if defined(CONFIG_PREEMPT_RT_BASE)
rt_invol = t->rt_invol_sleep;
#endif
WARN_ON_ONCE(!preempt && t->rcu_read_lock_nesting > 0 && !rt_invol);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e1bdd7f9be05..a151332474d8 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7405,7 +7405,11 @@ void migrate_enable(void)
unpin_current_cpu();
preempt_lazy_enable();
preempt_enable();
+
+ rt_invol_sleep_inc();
stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
+ rt_invol_sleep_dec();
+
return;
}
}
--
1.8.3.1