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') 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