linux-kernel - Re: [PATCH] rcu: Remove rcu

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Message-ID: <20121003183945.GP2527@linux.vnet.ibm.com>
Date:	Wed, 3 Oct 2012 11:39:45 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Josh Triplett <josh@...htriplett.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] rcu: Remove rcu_switch()

On Wed, Oct 03, 2012 at 08:21:52PM +0200, Frederic Weisbecker wrote:
> It's only there to call rcu_user_hooks_switch(). Let's
> just call rcu_user_hooks_switch() directly, we don't need this
> function in the middle.

Hello, Frederic!

Doesn't this also require an empty definition of rcu_user_hooks_switch()
to handle the CONFIG_RCU_USER_QS=n case?  Or is there already such
a definition that I am too blind to see?

							Thanx, Paul

> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Josh Triplett <josh@...htriplett.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> ---
>  include/linux/rcupdate.h |    2 ++
>  include/linux/sched.h    |    8 --------
>  kernel/sched/core.c      |    2 +-
>  3 files changed, 3 insertions(+), 9 deletions(-)
> 
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> index 7c968e4..5d009de 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -204,6 +204,8 @@ static inline void rcu_user_enter(void) { }
>  static inline void rcu_user_exit(void) { }
>  static inline void rcu_user_enter_after_irq(void) { }
>  static inline void rcu_user_exit_after_irq(void) { }
> +static inline void rcu_user_hooks_switch(struct task_struct *prev,
> +					 struct task_struct *next) { }
>  #endif /* CONFIG_RCU_USER_QS */
> 
>  extern void exit_rcu(void);
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 9d51e26..65e2694 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1886,14 +1886,6 @@ static inline void rcu_copy_process(struct task_struct *p)
> 
>  #endif
> 
> -static inline void rcu_switch(struct task_struct *prev,
> -			      struct task_struct *next)
> -{
> -#ifdef CONFIG_RCU_USER_QS
> -	rcu_user_hooks_switch(prev, next);
> -#endif
> -}
> -
>  static inline void tsk_restore_flags(struct task_struct *task,
>  				unsigned long orig_flags, unsigned long flags)
>  {
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index c177472..a48bef7 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1887,7 +1887,7 @@ context_switch(struct rq *rq, struct task_struct *prev,
>  #endif
> 
>  	/* Here we just switch the register state and the stack. */
> -	rcu_switch(prev, next);
> +	rcu_user_hooks_switch(prev, next);
>  	switch_to(prev, next, prev);
> 
>  	barrier();
> -- 
> 1.7.5.4
> 

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