From c7580c1e84435c9ccc6c612d9fee8e71811f7be6 Mon Sep 17 00:00:00 2001 From: Waiman Long Date: Thu, 4 Apr 2019 13:43:11 -0400 Subject: locking/rwsem: Move owner setting code from rwsem.c to rwsem.h Move all the owner setting code closer to the rwsem-xadd fast paths directly within rwsem.h file as well as in the slowpaths where owner setting is done after acquring the lock. This will enable us to add DEBUG_RWSEMS check in a later patch to make sure that read lock is really acquired when rwsem_down_read_failed() returns, for instance. Signed-off-by: Waiman Long Acked-by: Peter Zijlstra Acked-by: Davidlohr Bueso Cc: Andrew Morton Cc: Arnd Bergmann Cc: Borislav Petkov Cc: Davidlohr Bueso Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Tim Chen Cc: Will Deacon Link: http://lkml.kernel.org/r/20190404174320.22416-3-longman@redhat.com Signed-off-by: Ingo Molnar --- kernel/locking/rwsem.c | 19 ++----------------- 1 file changed, 2 insertions(+), 17 deletions(-) (limited to 'kernel/locking/rwsem.c') diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index e586f0d03ad3..59e584895532 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -24,7 +24,6 @@ void __sched down_read(struct rw_semaphore *sem) rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_); LOCK_CONTENDED(sem, __down_read_trylock, __down_read); - rwsem_set_reader_owned(sem); } EXPORT_SYMBOL(down_read); @@ -39,7 +38,6 @@ int __sched down_read_killable(struct rw_semaphore *sem) return -EINTR; } - rwsem_set_reader_owned(sem); return 0; } @@ -52,10 +50,8 @@ int down_read_trylock(struct rw_semaphore *sem) { int ret = __down_read_trylock(sem); - if (ret == 1) { + if (ret == 1) rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_); - rwsem_set_reader_owned(sem); - } return ret; } @@ -70,7 +66,6 @@ void __sched down_write(struct rw_semaphore *sem) rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_); LOCK_CONTENDED(sem, __down_write_trylock, __down_write); - rwsem_set_owner(sem); } EXPORT_SYMBOL(down_write); @@ -88,7 +83,6 @@ int __sched down_write_killable(struct rw_semaphore *sem) return -EINTR; } - rwsem_set_owner(sem); return 0; } @@ -101,10 +95,8 @@ int down_write_trylock(struct rw_semaphore *sem) { int ret = __down_write_trylock(sem); - if (ret == 1) { + if (ret == 1) rwsem_acquire(&sem->dep_map, 0, 1, _RET_IP_); - rwsem_set_owner(sem); - } return ret; } @@ -119,7 +111,6 @@ void up_read(struct rw_semaphore *sem) rwsem_release(&sem->dep_map, 1, _RET_IP_); DEBUG_RWSEMS_WARN_ON(!((unsigned long)sem->owner & RWSEM_READER_OWNED)); - rwsem_clear_reader_owned(sem); __up_read(sem); } @@ -133,7 +124,6 @@ void up_write(struct rw_semaphore *sem) rwsem_release(&sem->dep_map, 1, _RET_IP_); DEBUG_RWSEMS_WARN_ON(sem->owner != current); - rwsem_clear_owner(sem); __up_write(sem); } @@ -147,7 +137,6 @@ void downgrade_write(struct rw_semaphore *sem) lock_downgrade(&sem->dep_map, _RET_IP_); DEBUG_RWSEMS_WARN_ON(sem->owner != current); - rwsem_set_reader_owned(sem); __downgrade_write(sem); } @@ -161,7 +150,6 @@ void down_read_nested(struct rw_semaphore *sem, int subclass) rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_); LOCK_CONTENDED(sem, __down_read_trylock, __down_read); - rwsem_set_reader_owned(sem); } EXPORT_SYMBOL(down_read_nested); @@ -172,7 +160,6 @@ void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest) rwsem_acquire_nest(&sem->dep_map, 0, 0, nest, _RET_IP_); LOCK_CONTENDED(sem, __down_write_trylock, __down_write); - rwsem_set_owner(sem); } EXPORT_SYMBOL(_down_write_nest_lock); @@ -193,7 +180,6 @@ void down_write_nested(struct rw_semaphore *sem, int subclass) rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_); LOCK_CONTENDED(sem, __down_write_trylock, __down_write); - rwsem_set_owner(sem); } EXPORT_SYMBOL(down_write_nested); @@ -208,7 +194,6 @@ int __sched down_write_killable_nested(struct rw_semaphore *sem, int subclass) return -EINTR; } - rwsem_set_owner(sem); return 0; } -- cgit v1.2.3 From a68e2c4c637918da47b3aa270051545cff7d8245 Mon Sep 17 00:00:00 2001 From: Waiman Long Date: Thu, 4 Apr 2019 13:43:14 -0400 Subject: locking/rwsem: Add debug check for __down_read*() When rwsem_down_read_failed*() return, the read lock is acquired indirectly by others. So debug checks are added in __down_read() and __down_read_killable() to make sure the rwsem is really reader-owned. The other debug check calls in kernel/locking/rwsem.c except the one in up_read_non_owner() are also moved over to rwsem-xadd.h. Signed-off-by: Waiman Long Acked-by: Peter Zijlstra Acked-by: Davidlohr Bueso Cc: Andrew Morton Cc: Arnd Bergmann Cc: Borislav Petkov Cc: Davidlohr Bueso Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Tim Chen Cc: Will Deacon Link: http://lkml.kernel.org/r/20190404174320.22416-6-longman@redhat.com Signed-off-by: Ingo Molnar --- kernel/locking/rwsem.c | 3 --- kernel/locking/rwsem.h | 12 ++++++++++-- 2 files changed, 10 insertions(+), 5 deletions(-) (limited to 'kernel/locking/rwsem.c') diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 59e584895532..90de5f1780ba 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -109,7 +109,6 @@ EXPORT_SYMBOL(down_write_trylock); void up_read(struct rw_semaphore *sem) { rwsem_release(&sem->dep_map, 1, _RET_IP_); - DEBUG_RWSEMS_WARN_ON(!((unsigned long)sem->owner & RWSEM_READER_OWNED)); __up_read(sem); } @@ -122,7 +121,6 @@ EXPORT_SYMBOL(up_read); void up_write(struct rw_semaphore *sem) { rwsem_release(&sem->dep_map, 1, _RET_IP_); - DEBUG_RWSEMS_WARN_ON(sem->owner != current); __up_write(sem); } @@ -135,7 +133,6 @@ EXPORT_SYMBOL(up_write); void downgrade_write(struct rw_semaphore *sem) { lock_downgrade(&sem->dep_map, _RET_IP_); - DEBUG_RWSEMS_WARN_ON(sem->owner != current); __downgrade_write(sem); } diff --git a/kernel/locking/rwsem.h b/kernel/locking/rwsem.h index 19997c82270b..1d8f722a6761 100644 --- a/kernel/locking/rwsem.h +++ b/kernel/locking/rwsem.h @@ -165,10 +165,13 @@ extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem); */ static inline void __down_read(struct rw_semaphore *sem) { - if (unlikely(atomic_long_inc_return_acquire(&sem->count) <= 0)) + if (unlikely(atomic_long_inc_return_acquire(&sem->count) <= 0)) { rwsem_down_read_failed(sem); - else + DEBUG_RWSEMS_WARN_ON(!((unsigned long)sem->owner & + RWSEM_READER_OWNED)); + } else { rwsem_set_reader_owned(sem); + } } static inline int __down_read_killable(struct rw_semaphore *sem) @@ -176,6 +179,8 @@ static inline int __down_read_killable(struct rw_semaphore *sem) if (unlikely(atomic_long_inc_return_acquire(&sem->count) <= 0)) { if (IS_ERR(rwsem_down_read_failed_killable(sem))) return -EINTR; + DEBUG_RWSEMS_WARN_ON(!((unsigned long)sem->owner & + RWSEM_READER_OWNED)); } else { rwsem_set_reader_owned(sem); } @@ -246,6 +251,7 @@ static inline void __up_read(struct rw_semaphore *sem) { long tmp; + DEBUG_RWSEMS_WARN_ON(!((unsigned long)sem->owner & RWSEM_READER_OWNED)); rwsem_clear_reader_owned(sem); tmp = atomic_long_dec_return_release(&sem->count); if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0)) @@ -257,6 +263,7 @@ static inline void __up_read(struct rw_semaphore *sem) */ static inline void __up_write(struct rw_semaphore *sem) { + DEBUG_RWSEMS_WARN_ON(sem->owner != current); rwsem_clear_owner(sem); if (unlikely(atomic_long_sub_return_release(RWSEM_ACTIVE_WRITE_BIAS, &sem->count) < 0)) @@ -277,6 +284,7 @@ static inline void __downgrade_write(struct rw_semaphore *sem) * read-locked region is ok to be re-ordered into the * write side. As such, rely on RELEASE semantics. */ + DEBUG_RWSEMS_WARN_ON(sem->owner != current); tmp = atomic_long_add_return_release(-RWSEM_WAITING_BIAS, &sem->count); rwsem_set_reader_owned(sem); if (tmp < 0) -- cgit v1.2.3 From 3b4ba6643d26a95e08067fca9a5da1828f9afabf Mon Sep 17 00:00:00 2001 From: Waiman Long Date: Thu, 4 Apr 2019 13:43:15 -0400 Subject: locking/rwsem: Enhance DEBUG_RWSEMS_WARN_ON() macro Currently, the DEBUG_RWSEMS_WARN_ON() macro just dumps a stack trace when the rwsem isn't in the right state. It does not show the actual states of the rwsem. This may not be that helpful in the debugging process. Enhance the DEBUG_RWSEMS_WARN_ON() macro to also show the current content of the rwsem count and owner fields to give more information about what is wrong with the rwsem. The debug_locks_off() function is called as is done inside DEBUG_LOCKS_WARN_ON(). Signed-off-by: Waiman Long Acked-by: Peter Zijlstra Acked-by: Davidlohr Bueso Cc: Andrew Morton Cc: Arnd Bergmann Cc: Borislav Petkov Cc: Davidlohr Bueso Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Tim Chen Cc: Will Deacon Link: http://lkml.kernel.org/r/20190404174320.22416-7-longman@redhat.com Signed-off-by: Ingo Molnar --- kernel/locking/rwsem.c | 3 ++- kernel/locking/rwsem.h | 21 ++++++++++++++------- 2 files changed, 16 insertions(+), 8 deletions(-) (limited to 'kernel/locking/rwsem.c') diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 90de5f1780ba..ccbf18f560ff 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -198,7 +198,8 @@ EXPORT_SYMBOL(down_write_killable_nested); void up_read_non_owner(struct rw_semaphore *sem) { - DEBUG_RWSEMS_WARN_ON(!((unsigned long)sem->owner & RWSEM_READER_OWNED)); + DEBUG_RWSEMS_WARN_ON(!((unsigned long)sem->owner & RWSEM_READER_OWNED), + sem); __up_read(sem); } diff --git a/kernel/locking/rwsem.h b/kernel/locking/rwsem.h index 1d8f722a6761..3059a2dc39f8 100644 --- a/kernel/locking/rwsem.h +++ b/kernel/locking/rwsem.h @@ -27,9 +27,15 @@ #define RWSEM_ANONYMOUSLY_OWNED (1UL << 1) #ifdef CONFIG_DEBUG_RWSEMS -# define DEBUG_RWSEMS_WARN_ON(c) DEBUG_LOCKS_WARN_ON(c) +# define DEBUG_RWSEMS_WARN_ON(c, sem) do { \ + if (WARN_ONCE(c, "DEBUG_RWSEMS_WARN_ON(%s): count = 0x%lx, owner = 0x%lx, curr 0x%lx, list %sempty\n",\ + #c, atomic_long_read(&(sem)->count), \ + (long)((sem)->owner), (long)current, \ + list_empty(&(sem)->wait_list) ? "" : "not ")) \ + debug_locks_off(); \ + } while (0) #else -# define DEBUG_RWSEMS_WARN_ON(c) +# define DEBUG_RWSEMS_WARN_ON(c, sem) #endif /* @@ -168,7 +174,7 @@ static inline void __down_read(struct rw_semaphore *sem) if (unlikely(atomic_long_inc_return_acquire(&sem->count) <= 0)) { rwsem_down_read_failed(sem); DEBUG_RWSEMS_WARN_ON(!((unsigned long)sem->owner & - RWSEM_READER_OWNED)); + RWSEM_READER_OWNED), sem); } else { rwsem_set_reader_owned(sem); } @@ -180,7 +186,7 @@ static inline int __down_read_killable(struct rw_semaphore *sem) if (IS_ERR(rwsem_down_read_failed_killable(sem))) return -EINTR; DEBUG_RWSEMS_WARN_ON(!((unsigned long)sem->owner & - RWSEM_READER_OWNED)); + RWSEM_READER_OWNED), sem); } else { rwsem_set_reader_owned(sem); } @@ -251,7 +257,8 @@ static inline void __up_read(struct rw_semaphore *sem) { long tmp; - DEBUG_RWSEMS_WARN_ON(!((unsigned long)sem->owner & RWSEM_READER_OWNED)); + DEBUG_RWSEMS_WARN_ON(!((unsigned long)sem->owner & RWSEM_READER_OWNED), + sem); rwsem_clear_reader_owned(sem); tmp = atomic_long_dec_return_release(&sem->count); if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0)) @@ -263,7 +270,7 @@ static inline void __up_read(struct rw_semaphore *sem) */ static inline void __up_write(struct rw_semaphore *sem) { - DEBUG_RWSEMS_WARN_ON(sem->owner != current); + DEBUG_RWSEMS_WARN_ON(sem->owner != current, sem); rwsem_clear_owner(sem); if (unlikely(atomic_long_sub_return_release(RWSEM_ACTIVE_WRITE_BIAS, &sem->count) < 0)) @@ -284,7 +291,7 @@ static inline void __downgrade_write(struct rw_semaphore *sem) * read-locked region is ok to be re-ordered into the * write side. As such, rely on RELEASE semantics. */ - DEBUG_RWSEMS_WARN_ON(sem->owner != current); + DEBUG_RWSEMS_WARN_ON(sem->owner != current, sem); tmp = atomic_long_add_return_release(-RWSEM_WAITING_BIAS, &sem->count); rwsem_set_reader_owned(sem); if (tmp < 0) -- cgit v1.2.3