On Thu, Feb 04, 2016 at 12:45:12AM +0800, Boqun Feng wrote: > The variables protected by an RCU read-side critical section are > sometimes hard to figure out, especially when the critical section is > long or has some function calls in it. However, figuring out which > variable a RCU read-side critical section protects could save > us a lot of time for code reviewing, bug fixing or performance tuning. > > This patch therefore uses the LOCKED_ACCESS to collect the information > of relationship between rcu_dereference*() and rcu_read_lock*() by > doing: > > Step 0: define a locked_access_class for RCU. > > Step 1: set the content of rcu_*_lock_key and __srcu_key to the > address of the locked_access_class for RCU. > > Step 2: add locked_access_point() in __rcu_dereference_check() > > After that we can figure out not only in which RCU read-side critical > section but also after which rcu_read_lock*() called an > rcu_dereference*() is called. > > This feature is controlled by a config option RCU_LOCKED_ACCESS. > > Also clean up the initialization code of lockdep_maps for different > flavors of RCU a little bit. > > Signed-off-by: Boqun Feng <boqun.f...@gmail.com> > --- > include/linux/rcupdate.h | 8 ++++++++ > include/linux/srcu.h | 8 +++++++- > kernel/locking/lockdep.c | 3 +++ > kernel/rcu/update.c | 31 +++++++++++++++++-------------- > lib/Kconfig.debug | 12 ++++++++++++ > 5 files changed, 47 insertions(+), 15 deletions(-) > > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h > index 14e6f47..4bab658 100644 > --- a/include/linux/rcupdate.h > +++ b/include/linux/rcupdate.h > @@ -610,6 +610,13 @@ static inline void rcu_preempt_sleep_check(void) > #define rcu_dereference_sparse(p, space) > #endif /* #else #ifdef __CHECKER__ */ > > +#ifdef CONFIG_RCU_LOCKED_ACCESS > +extern struct locked_access_class rcu_laclass; > +#define rcu_dereference_access() \ > + locked_access_point(&rcu_laclass, LOCKED_ACCESS_TYPE_READ) > +#else /* #ifdef CONFIG_LOCKED_ACCESS */ > +#define rcu_dereference_access() > +#endif /* #else #ifdef CONFIG_LOCKED_ACCESS */ > #define __rcu_access_pointer(p, space) \ > ({ \ > typeof(*p) *_________p1 = (typeof(*p) *__force)READ_ONCE(p); \ > @@ -622,6 +629,7 @@ static inline void rcu_preempt_sleep_check(void) > typeof(*p) *________p1 = (typeof(*p) *__force)lockless_dereference(p); \ > RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_check() usage"); \ > rcu_dereference_sparse(p, space); \ > + rcu_dereference_access(); \ > ((typeof(*p) __force __kernel *)(________p1)); \ > }) > #define __rcu_dereference_protected(p, c, space) \ > diff --git a/include/linux/srcu.h b/include/linux/srcu.h > index f5f80c5..ff048a2 100644 > --- a/include/linux/srcu.h > +++ b/include/linux/srcu.h > @@ -64,12 +64,18 @@ struct srcu_struct { > > #ifdef CONFIG_DEBUG_LOCK_ALLOC > > +# ifdef CONFIG_RCU_LOCKED_ACCESS > +# define RCU_KEY { .laclass = &rcu_laclass } > +# else > +# define RCU_KEY { 0 } > +# endif > + > int __init_srcu_struct(struct srcu_struct *sp, const char *name, > struct lock_class_key *key); > > #define init_srcu_struct(sp) \ > ({ \ > - static struct lock_class_key __srcu_key; \ > + static struct lock_class_key __srcu_key = RCU_KEY; \
This gets me the following for the TASKS01, TINY02, TREE02, TREE05, TREE06, and TREE08 configurations: CC mm/mmap.o In file included from /home/paulmck/public_git/linux-rcu/include/linux/notifier.h:15:0, from /home/paulmck/public_git/linux-rcu/arch/x86/include/asm/kdebug.h:4, from /home/paulmck/public_git/linux-rcu/include/linux/kdebug.h:4, from /home/paulmck/public_git/linux-rcu/kernel/notifier.c:1: /home/paulmck/public_git/linux-rcu/kernel/notifier.c: In function ‘srcu_init_notifier_head’: /home/paulmck/public_git/linux-rcu/include/linux/srcu.h:78:16: warning: missing braces around initializer [-Wmissing-braces] static struct lock_class_key __srcu_key = RCU_KEY; \ ^ /home/paulmck/public_git/linux-rcu/kernel/notifier.c:526:6: note: in expansion of macro ‘init_srcu_struct’ if (init_srcu_struct(&nh->srcu) < 0) ^ /home/paulmck/public_git/linux-rcu/include/linux/srcu.h:78:16: warning: (near initialization for ‘__srcu_key.subkeys’) [-Wmissing-braces] static struct lock_class_key __srcu_key = RCU_KEY; \ ^ /home/paulmck/public_git/linux-rcu/kernel/notifier.c:526:6: note: in expansion of macro ‘init_srcu_struct’ if (init_srcu_struct(&nh->srcu) < 0) ^ These have the following in their .config files: CONFIG_DEBUG_LOCK_ALLOC=y However, none of your new Kconfig options are set, which needs to be tested because this will be the common case. Several of them have CONFIG_PROVE_LOCKING=y, but others do not. I have dequeued these for the moment. Please send an updated patch series when you have this fixed. Thanx, Paul > \ > __init_srcu_struct((sp), #sp, &__srcu_key); \ > }) > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c > index 996c2d5..36bd0cc 100644 > --- a/kernel/locking/lockdep.c > +++ b/kernel/locking/lockdep.c > @@ -4623,5 +4623,8 @@ void locked_access(struct locked_access_class *laclass, > correlate_locked_access(laclass, acqchain, loc, type); > } > EXPORT_SYMBOL(locked_access); > +#ifdef CONFIG_RCU_LOCKED_ACCESS > +DEFINE_LACLASS(rcu); > +#endif > > #endif /* CONFIG_LOCKED_ACCESS */ > diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c > index 76b94e1..ba2ded6 100644 > --- a/kernel/rcu/update.c > +++ b/kernel/rcu/update.c > @@ -235,20 +235,23 @@ EXPORT_SYMBOL_GPL(__rcu_read_unlock); > #endif /* #ifdef CONFIG_PREEMPT_RCU */ > > #ifdef CONFIG_DEBUG_LOCK_ALLOC > -static struct lock_class_key rcu_lock_key; > -struct lockdep_map rcu_lock_map = > - STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key); > -EXPORT_SYMBOL_GPL(rcu_lock_map); > - > -static struct lock_class_key rcu_bh_lock_key; > -struct lockdep_map rcu_bh_lock_map = > - STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key); > -EXPORT_SYMBOL_GPL(rcu_bh_lock_map); > - > -static struct lock_class_key rcu_sched_lock_key; > -struct lockdep_map rcu_sched_lock_map = > - STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key); > -EXPORT_SYMBOL_GPL(rcu_sched_lock_map); > + > +# ifdef CONFIG_RCU_LOCKED_ACCESS > +# define RCU_KEY { .laclass = &rcu_laclass } > +# else > +# define RCU_KEY { 0 } > +# endif > + > +#define DEFINE_RCU_LOCKDEP_MAP(flavor) > \ > + static struct lock_class_key rcu##flavor##_lock_key = RCU_KEY; \ > + struct lockdep_map rcu##flavor##_lock_map = \ > + STATIC_LOCKDEP_MAP_INIT("rcu" #flavor "_read_lock", \ > + &rcu##flavor##_lock_key); \ > + EXPORT_SYMBOL_GPL(rcu##flavor##_lock_map) > + > +DEFINE_RCU_LOCKDEP_MAP(); > +DEFINE_RCU_LOCKDEP_MAP(_bh); > +DEFINE_RCU_LOCKDEP_MAP(_sched); > > static struct lock_class_key rcu_callback_key; > struct lockdep_map rcu_callback_map = > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index 178f288..b6003d4 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -1410,6 +1410,18 @@ config RCU_EQS_DEBUG > Say N here if you need ultimate kernel/user switch latencies > Say Y if you are unsure > > +config RCU_LOCKED_ACCESS > + bool "Track data access in RCU read-side critical sections" > + depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT > && LOCKDEP_SUPPORT > + select LOCKED_ACCESS > + default n > + help > + Track data acces in RCU read-side critical sections, > + by doing so, one can examine which rcu_dereference() and its > + friends are called in which RCU read-side critical sections, > + and even more detailed, after which rcu_read_lock() and > + its friends are called. > + > endmenu # "RCU Debugging" > > config DEBUG_BLOCK_EXT_DEVT > -- > 2.7.0 >