The following commit has been merged into the x86/entry branch of tip:
Commit-ID: 07325d4a90d2d84de45cc07b134fd0f023dbb971
Gitweb: https://git.kernel.org/tip/07325d4a90d2d84de45cc07b134fd0f023dbb971
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Thu, 21 May 2020 22:05:16 +02:00
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Tue, 26 May 2020 19:05:11 +02:00
rcu: Provide rcu_irq_exit_check_preempt()
Provide a debug check which can be invoked from exception return to kernel
mode before an attempt is made to schedule. Warn if RCU is not ready for
this.
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200521202117.089709607@xxxxxxxxxxxxx
---
include/linux/rcutiny.h | 1 +
include/linux/rcutree.h | 6 ++++++
kernel/rcu/tree.c | 18 ++++++++++++++++++
3 files changed, 25 insertions(+)
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index c869fb2..8512cae 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -72,6 +72,7 @@ static inline void rcu_irq_exit_irqson(void) { }
static inline void rcu_irq_enter_irqson(void) { }
static inline void rcu_irq_exit(void) { }
static inline void rcu_irq_exit_preempt(void) { }
+static inline void rcu_irq_exit_check_preempt(void) { }
static inline void exit_rcu(void) { }
static inline bool rcu_preempt_need_deferred_qs(struct task_struct *t)
{
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 9366fa4..d5cc9d6 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -51,6 +51,12 @@ void rcu_irq_exit_preempt(void);
void rcu_irq_enter_irqson(void);
void rcu_irq_exit_irqson(void);
+#ifdef CONFIG_PROVE_RCU
+void rcu_irq_exit_check_preempt(void);
+#else
+static inline void rcu_irq_exit_check_preempt(void) { }
+#endif
+
void exit_rcu(void);
void rcu_scheduler_starting(void);
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index b7f8c49..d8e9dbb 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -765,6 +765,24 @@ void rcu_irq_exit_preempt(void)
"RCU in extended quiescent state!");
}
+#ifdef CONFIG_PROVE_RCU
+/**
+ * rcu_irq_exit_check_preempt - Validate that scheduling is possible
+ */
+void rcu_irq_exit_check_preempt(void)
+{
+ lockdep_assert_irqs_disabled();
+
+ RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nesting) <= 0,
+ "RCU dynticks_nesting counter underflow/zero!");
+ RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) !=
+ DYNTICK_IRQ_NONIDLE,
+ "Bad RCU dynticks_nmi_nesting counter\n");
+ RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(),
+ "RCU in extended quiescent state!");
+}
+#endif /* #ifdef CONFIG_PROVE_RCU */
+
/*
* Wrapper for rcu_irq_exit() where interrupts are enabled.
*
|