Re: [PATCH 1/1] rcu_sync: Cleanup the CONFIG_PROVE_RCU checks

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Fri, Sep 11, 2015 at 05:59:18PM +0200, Oleg Nesterov wrote:
> 1. Rename __rcu_sync_is_idle() to rcu_sync_lockdep_assert() and
>    change it to use rcu_lockdep_assert().
> 
> 2. Change rcu_sync_is_idle() to return rsp->gp_state == GP_IDLE
>    unconditonally, this way we can remove the same check from
>    rcu_sync_lockdep_assert() and clearly isolate the debugging
>    code.
> 
> Note: rcu_sync_enter()->wait_event(gp_state == GP_PASSED) needs
> another CONFIG_PROVE_RCU check, the same we do in ->sync(); but
> this needs some simple preparations in the core RCU code to avoid
> the code duplication.
> 
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>

Queued for v4.4, thank you, Oleg!

							Thanx, Paul

> ---
>  include/linux/rcu_sync.h |    7 +++----
>  kernel/rcu/sync.c        |    6 +++---
>  2 files changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/include/linux/rcu_sync.h b/include/linux/rcu_sync.h
> index 8069d64..a63a33e 100644
> --- a/include/linux/rcu_sync.h
> +++ b/include/linux/rcu_sync.h
> @@ -40,7 +40,7 @@ struct rcu_sync {
>  	enum rcu_sync_type	gp_type;
>  };
> 
> -extern bool __rcu_sync_is_idle(struct rcu_sync *);
> +extern void rcu_sync_lockdep_assert(struct rcu_sync *);
> 
>  /**
>   * rcu_sync_is_idle() - Are readers permitted to use their fastpaths?
> @@ -53,10 +53,9 @@ extern bool __rcu_sync_is_idle(struct rcu_sync *);
>  static inline bool rcu_sync_is_idle(struct rcu_sync *rsp)
>  {
>  #ifdef CONFIG_PROVE_RCU
> -	return __rcu_sync_is_idle(rsp);
> -#else
> -	return !rsp->gp_state; /* GP_IDLE */
> +	rcu_sync_lockdep_assert(rsp);
>  #endif
> +	return !rsp->gp_state; /* GP_IDLE */
>  }
> 
>  extern void rcu_sync_init(struct rcu_sync *, enum rcu_sync_type);
> diff --git a/kernel/rcu/sync.c b/kernel/rcu/sync.c
> index 1c73c57..a8cf199 100644
> --- a/kernel/rcu/sync.c
> +++ b/kernel/rcu/sync.c
> @@ -63,10 +63,10 @@ enum { CB_IDLE = 0, CB_PENDING, CB_REPLAY };
>  #define	rss_lock	gp_wait.lock
> 
>  #ifdef CONFIG_PROVE_RCU
> -bool __rcu_sync_is_idle(struct rcu_sync *rsp)
> +void rcu_sync_lockdep_assert(struct rcu_sync *rsp)
>  {
> -	WARN_ON(!gp_ops[rsp->gp_type].held());
> -	return rsp->gp_state == GP_IDLE;
> +	rcu_lockdep_assert(gp_ops[rsp->gp_type].held(),
> +			   "suspicious rcu_sync_is_idle() usage");
>  }
>  #endif
> 
> -- 
> 1.5.5.1
> 
>