Re: [PATCH v3 06/22] rcu: Rename rcu_irq_{enter,exit}_irqson()

[Paul E. McKenney]

On Wed, Feb 19, 2020 at 03:47:30PM +0100, Peter Zijlstra wrote:
> The functions do in fact use local_irq_{save,restore}() and can
> therefore be used when IRQs are in fact disabled. Worse, they are
> already used in places where IRQs are disabled, leading to great
> confusion when reading the code.
> 
> Rename them to fix this confusion.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>

My first reaction was "Hey, wait, where is the _irqrestore()?"

Nevertheless, especially since these are the only _irqson() functions:

Reviewed-by: Paul E. McKenney <paulmck@xxxxxxxxxx>

> ---
>  include/linux/rcupdate.h   |    4 ++--
>  include/linux/rcutiny.h    |    4 ++--
>  include/linux/rcutree.h    |    4 ++--
>  include/linux/tracepoint.h |    4 ++--
>  kernel/cpu_pm.c            |    4 ++--
>  kernel/rcu/tree.c          |    8 ++++----
>  kernel/trace/trace.c       |    4 ++--
>  7 files changed, 16 insertions(+), 16 deletions(-)
> 
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -120,9 +120,9 @@ static inline void rcu_init_nohz(void) {
>   */
>  #define RCU_NONIDLE(a) \
>  	do { \
> -		rcu_irq_enter_irqson(); \
> +		rcu_irq_enter_irqsave(); \
>  		do { a; } while (0); \
> -		rcu_irq_exit_irqson(); \
> +		rcu_irq_exit_irqsave(); \
>  	} while (0)
>  
>  /*
> --- a/include/linux/rcutiny.h
> +++ b/include/linux/rcutiny.h
> @@ -68,8 +68,8 @@ static inline int rcu_jiffies_till_stall
>  static inline void rcu_idle_enter(void) { }
>  static inline void rcu_idle_exit(void) { }
>  static inline void rcu_irq_enter(void) { }
> -static inline void rcu_irq_exit_irqson(void) { }
> -static inline void rcu_irq_enter_irqson(void) { }
> +static inline void rcu_irq_exit_irqsave(void) { }
> +static inline void rcu_irq_enter_irqsave(void) { }
>  static inline void rcu_irq_exit(void) { }
>  static inline void exit_rcu(void) { }
>  static inline bool rcu_preempt_need_deferred_qs(struct task_struct *t)
> --- a/include/linux/rcutree.h
> +++ b/include/linux/rcutree.h
> @@ -46,8 +46,8 @@ void rcu_idle_enter(void);
>  void rcu_idle_exit(void);
>  void rcu_irq_enter(void);
>  void rcu_irq_exit(void);
> -void rcu_irq_enter_irqson(void);
> -void rcu_irq_exit_irqson(void);
> +void rcu_irq_enter_irqsave(void);
> +void rcu_irq_exit_irqsave(void);
>  
>  void exit_rcu(void);
>  
> --- a/include/linux/tracepoint.h
> +++ b/include/linux/tracepoint.h
> @@ -181,7 +181,7 @@ static inline struct tracepoint *tracepo
>  		 */							\
>  		if (rcuidle) {						\
>  			__idx = srcu_read_lock_notrace(&tracepoint_srcu);\
> -			rcu_irq_enter_irqson();				\
> +			rcu_irq_enter_irqsave();			\
>  		}							\
>  									\
>  		it_func_ptr = rcu_dereference_raw((tp)->funcs);		\
> @@ -195,7 +195,7 @@ static inline struct tracepoint *tracepo
>  		}							\
>  									\
>  		if (rcuidle) {						\
> -			rcu_irq_exit_irqson();				\
> +			rcu_irq_exit_irqsave();				\
>  			srcu_read_unlock_notrace(&tracepoint_srcu, __idx);\
>  		}							\
>  									\
> --- a/kernel/cpu_pm.c
> +++ b/kernel/cpu_pm.c
> @@ -24,10 +24,10 @@ static int cpu_pm_notify(enum cpu_pm_eve
>  	 * could be disfunctional in cpu idle. Copy RCU_NONIDLE code to let
>  	 * RCU know this.
>  	 */
> -	rcu_irq_enter_irqson();
> +	rcu_irq_enter_irqsave();
>  	ret = __atomic_notifier_call_chain(&cpu_pm_notifier_chain, event, NULL,
>  		nr_to_call, nr_calls);
> -	rcu_irq_exit_irqson();
> +	rcu_irq_exit_irqsave();
>  
>  	return notifier_to_errno(ret);
>  }
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -699,10 +699,10 @@ void rcu_irq_exit(void)
>  /*
>   * Wrapper for rcu_irq_exit() where interrupts are enabled.
>   *
> - * If you add or remove a call to rcu_irq_exit_irqson(), be sure to test
> + * If you add or remove a call to rcu_irq_exit_irqsave(), be sure to test
>   * with CONFIG_RCU_EQS_DEBUG=y.
>   */
> -void rcu_irq_exit_irqson(void)
> +void rcu_irq_exit_irqsave(void)
>  {
>  	unsigned long flags;
>  
> @@ -875,10 +875,10 @@ void rcu_irq_enter(void)
>  /*
>   * Wrapper for rcu_irq_enter() where interrupts are enabled.
>   *
> - * If you add or remove a call to rcu_irq_enter_irqson(), be sure to test
> + * If you add or remove a call to rcu_irq_enter_irqsave(), be sure to test
>   * with CONFIG_RCU_EQS_DEBUG=y.
>   */
> -void rcu_irq_enter_irqson(void)
> +void rcu_irq_enter_irqsave(void)
>  {
>  	unsigned long flags;
>  
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -3004,9 +3004,9 @@ void __trace_stack(struct trace_array *t
>  	if (unlikely(in_nmi()))
>  		return;
>  
> -	rcu_irq_enter_irqson();
> +	rcu_irq_enter_irqsave();
>  	__ftrace_trace_stack(buffer, flags, skip, pc, NULL);
> -	rcu_irq_exit_irqson();
> +	rcu_irq_exit_irqsave();
>  }
>  
>  /**
> 
>