locking/rwsem: Make owner available even if !CONFIG_RWSEM_SPIN_ON_OWNER

The owner field in the rw_semaphore structure is used primarily for optimistic spinning. However, identifying the rwsem owner can also be helpful in debugging as well as tracing locking related issues when analyzing crash dump. The owner field may also store state information that can be important to the operation of the rwsem. So the owner field is now made a permanent member of the rw_semaphore structure irrespective of CONFIG_RWSEM_SPIN_ON_OWNER.

Waiman Long committed 7 years ago

Commit c71fd891 parent 69d927b4 files · +10 −32Browse files

Showing the changes to kernel (2 of 4 files). Show all

Unified · Split

2 files

kernel/locking/rwsem-xadd.c +1 −1
kernel/locking/rwsem.h +0 −23

kernel/locking/rwsem-xadd.c+1−1

@@ -86,8 +86,8 @@ void __init_rwsem(struct rw_semaphore sem, const char name, · 85 unmodified lines
86	86	atomic_long_set(&sem->count, RWSEM_UNLOCKED_VALUE);
87	87	raw_spin_lock_init(&sem->wait_lock);
88	88	INIT_LIST_HEAD(&sem->wait_list);
89		−#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
90	89	sem->owner = NULL;
	90	+#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
91	91	osq_lock_init(&sem->osq);
92	92	#endif
93	93	}

kernel/locking/rwsem.h+0−23

@@ -61,7 +61,6 @@ · 60 unmodified lines
61	61	#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
62	62	#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
63	63
64		−#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
65	64	/*
66	65	* All writes to owner are protected by WRITE_ONCE() to make sure that
67	66	* store tearing can't happen as optimistic spinners may read and use
@@ -126,7 +125,6 @@ static inline bool rwsem_has_anonymous_owner(struct task_struct *owner) · 58 unmodified lines
126	125	* real owner or one of the real owners. The only exception is when the
127	126	* unlock is done by up_read_non_owner().
128	127	*/
129		−#define rwsem_clear_reader_owned rwsem_clear_reader_owned
130	128	static inline void rwsem_clear_reader_owned(struct rw_semaphore *sem)
131	129	{
132	130	unsigned long val = (unsigned long)current \| RWSEM_READER_OWNED
@@ -135,28 +133,7 @@ static inline void rwsem_clear_reader_owned(struct rw_semaphore *sem) · 2 unmodified lines
135	133	cmpxchg_relaxed((unsigned long *)&sem->owner, val,
136	134	RWSEM_READER_OWNED \| RWSEM_ANONYMOUSLY_OWNED);
137	135	}
138		−#endif
139		−
140	136	#else
141		−static inline void rwsem_set_owner(struct rw_semaphore *sem)
142		−{
143		−}
144		−
145		−static inline void rwsem_clear_owner(struct rw_semaphore *sem)
146		−{
147		−}
148		−
149		−static inline void __rwsem_set_reader_owned(struct rw_semaphore *sem,
150		− struct task_struct *owner)
151		−{
152		−}
153		−
154		−static inline void rwsem_set_reader_owned(struct rw_semaphore *sem)
155		−{
156		−}
157		−#endif
158		−
159		−#ifndef rwsem_clear_reader_owned
160	137	static inline void rwsem_clear_reader_owned(struct rw_semaphore *sem)
161	138	{
162	139	}