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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@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/r/20200521202117.089709607@linutronix.de
This commit is contained in:
Thomas Gleixner 2020-05-21 22:05:16 +02:00 committed by Ingo Molnar
parent aaf2bc50df
commit 07325d4a90
3 changed files with 25 additions and 0 deletions
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1
include/linux/rcutiny.h
View File

@ -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)
{

6
include/linux/rcutree.h
View File

@ -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);

18
kernel/rcu/tree.c
View File

@ -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.
*