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

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

> Paul E. McKenney wrote:
> > From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> >
> > Signed-off-by: Paul E. McKenney <paulmck@linux.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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