On 7/29/19 12:47 AM, Davidlohr Bueso wrote: > Currently rwsems is the only locking primitive that lacks this > debug feature. Add it under CONFIG_DEBUG_RWSEMS and do the magic > checking in the locking fastpath (trylock) operation such that > we cover all cases. The unlocking part is pretty straightforward. > > Signed-off-by: Davidlohr Bueso <[email protected]> > --- > include/linux/rwsem.h | 10 ++++++++++ > kernel/locking/rwsem.c | 22 ++++++++++++++++++---- > 2 files changed, 28 insertions(+), 4 deletions(-) > > diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h > index 9d9c663987d8..00d6054687dd 100644 > --- a/include/linux/rwsem.h > +++ b/include/linux/rwsem.h > @@ -45,6 +45,9 @@ struct rw_semaphore { > #endif > raw_spinlock_t wait_lock; > struct list_head wait_list; > +#ifdef CONFIG_DEBUG_RWSEMS > + void *magic; > +#endif > #ifdef CONFIG_DEBUG_LOCK_ALLOC > struct lockdep_map dep_map; > #endif > @@ -73,6 +76,12 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem) > # define __RWSEM_DEP_MAP_INIT(lockname) > #endif > > +#ifdef CONFIG_DEBUG_RWSEMS > +# define __DEBUG_RWSEM_INITIALIZER(lockname) , .magic = &lockname > +#else > +# define __DEBUG_RWSEM_INITIALIZER(lockname) > +#endif > + > #ifdef CONFIG_RWSEM_SPIN_ON_OWNER > #define __RWSEM_OPT_INIT(lockname) , .osq = OSQ_LOCK_UNLOCKED > #else > @@ -85,6 +94,7 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem) > .wait_list = LIST_HEAD_INIT((name).wait_list), \ > .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock) \ > __RWSEM_OPT_INIT(name) \ > + __DEBUG_RWSEM_INITIALIZER(name) \ > __RWSEM_DEP_MAP_INIT(name) } > > #define DECLARE_RWSEM(name) \ > diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c > index 37524a47f002..ab392ec51252 100644 > --- a/kernel/locking/rwsem.c > +++ b/kernel/locking/rwsem.c > @@ -105,8 +105,9 @@ > #ifdef CONFIG_DEBUG_RWSEMS > # define DEBUG_RWSEMS_WARN_ON(c, sem) do { \ > if (!debug_locks_silent && \ > - WARN_ONCE(c, "DEBUG_RWSEMS_WARN_ON(%s): count = 0x%lx, owner = > 0x%lx, curr 0x%lx, list %sempty\n",\ > + WARN_ONCE(c, "DEBUG_RWSEMS_WARN_ON(%s): count = 0x%lx, magic = > 0x%lx, owner = 0x%lx, curr 0x%lx, list %sempty\n",\ > #c, atomic_long_read(&(sem)->count), \ > + (unsigned long) sem->magic, \ > atomic_long_read(&(sem)->owner), (long)current, \ > list_empty(&(sem)->wait_list) ? "" : "not ")) \ > debug_locks_off(); \ > @@ -329,6 +330,9 @@ void __init_rwsem(struct rw_semaphore *sem, const char > *name, > */ > debug_check_no_locks_freed((void *)sem, sizeof(*sem)); > lockdep_init_map(&sem->dep_map, name, key, 0); > +#endif > +#ifdef CONFIG_DEBUG_RWSEMS > + sem->magic = sem; > #endif > atomic_long_set(&sem->count, RWSEM_UNLOCKED_VALUE); > raw_spin_lock_init(&sem->wait_lock); > @@ -1322,11 +1326,14 @@ static inline int __down_read_killable(struct > rw_semaphore *sem) > > static inline int __down_read_trylock(struct rw_semaphore *sem) > { > + long tmp; > + > + DEBUG_RWSEMS_WARN_ON(sem->magic != sem, sem); > + > /* > * Optimize for the case when the rwsem is not locked at all. > */ > - long tmp = RWSEM_UNLOCKED_VALUE; > - > + tmp = RWSEM_UNLOCKED_VALUE; > do { > if (atomic_long_try_cmpxchg_acquire(&sem->count, &tmp, > tmp + RWSEM_READER_BIAS)) { > @@ -1367,8 +1374,11 @@ static inline int __down_write_killable(struct > rw_semaphore *sem) > > static inline int __down_write_trylock(struct rw_semaphore *sem) > { > - long tmp = RWSEM_UNLOCKED_VALUE; > + long tmp; > > + DEBUG_RWSEMS_WARN_ON(sem->magic != sem, sem); > + > + tmp = RWSEM_UNLOCKED_VALUE; > if (atomic_long_try_cmpxchg_acquire(&sem->count, &tmp, > RWSEM_WRITER_LOCKED)) { > rwsem_set_owner(sem); > @@ -1384,7 +1394,9 @@ inline void __up_read(struct rw_semaphore *sem) > { > long tmp; > > + DEBUG_RWSEMS_WARN_ON(sem->magic != sem, sem); > DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem); > + > rwsem_clear_reader_owned(sem); > tmp = atomic_long_add_return_release(-RWSEM_READER_BIAS, &sem->count); > DEBUG_RWSEMS_WARN_ON(tmp < 0, sem); > @@ -1402,12 +1414,14 @@ static inline void __up_write(struct rw_semaphore > *sem) > { > long tmp; > > + DEBUG_RWSEMS_WARN_ON(sem->magic != sem, sem); > /* > * sem->owner may differ from current if the ownership is transferred > * to an anonymous writer by setting the RWSEM_NONSPINNABLE bits. > */ > DEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) && > !rwsem_test_oflags(sem, RWSEM_NONSPINNABLE), sem); > + > rwsem_clear_owner(sem); > tmp = atomic_long_fetch_add_release(-RWSEM_WRITER_LOCKED, &sem->count); > if (unlikely(tmp & RWSEM_FLAG_WAITERS))
Acked-by: Waiman Long <[email protected]> Thanks for the patch. -Longman
