linux-kernel - Re: [PATCH 1/5] rcu,nohz: add state parameter to context_tracking_user

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Date:	Thu, 5 Feb 2015 15:55:26 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	riel@...hat.com
Cc:	kvm@...r.kernel.org, borntraeger@...ibm.com,
	linux-kernel@...r.kernel.org, mtosatti@...hat.com,
	mingo@...nel.orgm, ak@...ux.intel.com, oleg@...hat.com,
	masami.hiramatsu.pt@...achi.com, fweisbec@...il.com,
	lcapitulino@...hat.com, pbonzini@...hat.com
Subject: Re: [PATCH 1/5] rcu,nohz: add state parameter to
 context_tracking_user_enter/exit

On Thu, Feb 05, 2015 at 03:23:48PM -0500, riel@...hat.com wrote:
> From: Rik van Riel <riel@...hat.com>
> 
> Add the expected ctx_state as a parameter to context_tracking_user_enter
> and context_tracking_user_exit, allowing the same functions to not just
> track kernel <> user space switching, but also kernel <> guest transitions.
> 
> Signed-off-by: Rik van Riel <riel@...hat.com>

Acked-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

> ---
>  include/linux/context_tracking.h | 12 ++++++------
>  kernel/context_tracking.c        | 10 +++++-----
>  2 files changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
> index 37b81bd51ec0..bd9f000fc98d 100644
> --- a/include/linux/context_tracking.h
> +++ b/include/linux/context_tracking.h
> @@ -10,21 +10,21 @@
>  #ifdef CONFIG_CONTEXT_TRACKING
>  extern void context_tracking_cpu_set(int cpu);
> 
> -extern void context_tracking_user_enter(void);
> -extern void context_tracking_user_exit(void);
> +extern void context_tracking_user_enter(enum ctx_state state);
> +extern void context_tracking_user_exit(enum ctx_state state);
>  extern void __context_tracking_task_switch(struct task_struct *prev,
>  					   struct task_struct *next);
> 
>  static inline void user_enter(void)
>  {
>  	if (context_tracking_is_enabled())
> -		context_tracking_user_enter();
> +		context_tracking_user_enter(IN_USER);
> 
>  }
>  static inline void user_exit(void)
>  {
>  	if (context_tracking_is_enabled())
> -		context_tracking_user_exit();
> +		context_tracking_user_exit(IN_USER);
>  }
> 
>  static inline enum ctx_state exception_enter(void)
> @@ -35,7 +35,7 @@ static inline enum ctx_state exception_enter(void)
>  		return 0;
> 
>  	prev_ctx = this_cpu_read(context_tracking.state);
> -	context_tracking_user_exit();
> +	context_tracking_user_exit(prev_ctx);
> 
>  	return prev_ctx;
>  }
> @@ -44,7 +44,7 @@ static inline void exception_exit(enum ctx_state prev_ctx)
>  {
>  	if (context_tracking_is_enabled()) {
>  		if (prev_ctx == IN_USER)
> -			context_tracking_user_enter();
> +			context_tracking_user_enter(prev_ctx);
>  	}
>  }
> 
> diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
> index 937ecdfdf258..4c010787c9ec 100644
> --- a/kernel/context_tracking.c
> +++ b/kernel/context_tracking.c
> @@ -47,7 +47,7 @@ void context_tracking_cpu_set(int cpu)
>   * to execute won't use any RCU read side critical section because this
>   * function sets RCU in extended quiescent state.
>   */
> -void context_tracking_user_enter(void)
> +void context_tracking_user_enter(enum ctx_state state)
>  {
>  	unsigned long flags;
> 
> @@ -75,7 +75,7 @@ void context_tracking_user_enter(void)
>  	WARN_ON_ONCE(!current->mm);
> 
>  	local_irq_save(flags);
> -	if ( __this_cpu_read(context_tracking.state) != IN_USER) {
> +	if ( __this_cpu_read(context_tracking.state) != state) {
>  		if (__this_cpu_read(context_tracking.active)) {
>  			trace_user_enter(0);
>  			/*
> @@ -101,7 +101,7 @@ void context_tracking_user_enter(void)
>  		 * OTOH we can spare the calls to vtime and RCU when context_tracking.active
>  		 * is false because we know that CPU is not tickless.
>  		 */
> -		__this_cpu_write(context_tracking.state, IN_USER);
> +		__this_cpu_write(context_tracking.state, state);
>  	}
>  	local_irq_restore(flags);
>  }
> @@ -118,7 +118,7 @@ NOKPROBE_SYMBOL(context_tracking_user_enter);
>   * This call supports re-entrancy. This way it can be called from any exception
>   * handler without needing to know if we came from userspace or not.
>   */
> -void context_tracking_user_exit(void)
> +void context_tracking_user_exit(enum ctx_state state)
>  {
>  	unsigned long flags;
> 
> @@ -129,7 +129,7 @@ void context_tracking_user_exit(void)
>  		return;
> 
>  	local_irq_save(flags);
> -	if (__this_cpu_read(context_tracking.state) == IN_USER) {
> +	if (__this_cpu_read(context_tracking.state) == state) {
>  		if (__this_cpu_read(context_tracking.active)) {
>  			/*
>  			 * We are going to run code that may use RCU. Inform
> -- 
> 1.9.3
> 

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