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 11:00:58 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, 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


* Lai Jiangshan <laijs@...fujitsu.com> wrote:

> 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.

ah, this would explain the crash i reported in:

    http://lkml.org/lkml/2009/8/23/170

	Ingo
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