linux-kernel - Re: [PATCH -tip] v3 Consolidate sparse and lockdep declarations in include/linux/rcupdate.h

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Date:	Mon, 24 Aug 2009 15:34:46 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
CC:	linux-kernel@...r.kernel.org, mingo@...e.hu, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...ymtl.ca,
	josht@...ux.vnet.ibm.com, dvhltc@...ibm.com, niv@...ibm.com,
	tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org
Subject: Re: [PATCH -tip] v3 Consolidate sparse and lockdep declarations in
 include/linux/rcupdate.h

Paul E. McKenney wrote:
> From: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> 
> Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> ---
>  include/linux/rcupdate.h   |   46 ++++++++++++++++++++++++++++++++++++++++---
>  include/linux/rcupreempt.h |    4 +-
>  include/linux/rcutree.h    |   18 -----------------
>  3 files changed, 44 insertions(+), 24 deletions(-)
> 
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> index e920f0f..9d85ee1 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -80,6 +80,16 @@ extern int rcu_scheduler_active;
>         (ptr)->next = NULL; (ptr)->func = NULL; \
>  } while (0)
>  
> +#ifdef CONFIG_DEBUG_LOCK_ALLOC
> +extern struct lockdep_map rcu_lock_map;
> +# define rcu_read_acquire()	\
> +			lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
> +# define rcu_read_release()	lock_release(&rcu_lock_map, 1, _THIS_IP_)
> +#else
> +# define rcu_read_acquire()	do { } while (0)
> +# define rcu_read_release()	do { } while (0)
> +#endif
> +
>  /**
>   * rcu_read_lock - mark the beginning of an RCU read-side critical section.
>   *
> @@ -109,7 +119,12 @@ extern int rcu_scheduler_active;
>   *
>   * It is illegal to block while in an RCU read-side critical section.
>   */
> -#define rcu_read_lock() __rcu_read_lock()
> +static inline void rcu_read_lock(void)
> +{
> +	__rcu_read_lock();
> +	__acquire(RCU);
> +	rcu_read_acquire();
> +}
>  
>  /**
>   * rcu_read_unlock - marks the end of an RCU read-side critical section.
> @@ -126,7 +141,12 @@ extern int rcu_scheduler_active;
>   * used as well.  RCU does not care how the writers keep out of each
>   * others' way, as long as they do so.
>   */
> -#define rcu_read_unlock() __rcu_read_unlock()
> +static inline void rcu_read_unlock(void)
> +{
> +	rcu_read_release();
> +	__release(RCU);
> +	__rcu_read_unlock();
> +}
>  
>  /**
>   * rcu_read_lock_bh - mark the beginning of a softirq-only RCU critical section
> @@ -139,14 +159,24 @@ extern int rcu_scheduler_active;
>   * can use just rcu_read_lock().
>   *
>   */
> -#define rcu_read_lock_bh() __rcu_read_lock_bh()
> +static inline void rcu_read_lock_bh(void)
> +{
> +	__rcu_read_lock_bh();
> +	__acquire(RCU_BH);
> +	rcu_read_acquire();
> +}
>  
>  /*
>   * rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section
>   *
>   * See rcu_read_lock_bh() for more information.
>   */
> -#define rcu_read_unlock_bh() __rcu_read_unlock_bh()
> +static inline void rcu_read_unlock_bh(void)
> +{
> +	rcu_read_release();
> +	__release(RCU_BH);
> +	__rcu_read_unlock_bh();
> +}
>  
>  /**
>   * rcu_read_lock_sched - mark the beginning of a RCU-classic critical section
> @@ -160,10 +190,14 @@ extern int rcu_scheduler_active;
>  static inline void rcu_read_lock_sched(void)
>  {
>  	preempt_disable();
> +	__acquire(RCU_SCHED);
> +	rcu_read_acquire();
>  }
>  static inline void rcu_read_lock_sched_notrace(void)

It need be marked "notrace" too.

>  {
>  	preempt_disable_notrace();
> +	__acquire(RCU_SCHED);
> +	rcu_read_acquire();
>  }
>  

It may cause infinity recursion.
rcu_read_acquire() calls rcu_read_lock_sched_notrace()
before current->lockdep_recursion is set to 1 when tracing in on,
thus infinity recursion occurs.

Lai

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