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

Unified · Split

4 files

include/linux/rwsem.h +5 −4
kernel/locking/rwsem-xadd.c +1 −1
kernel/locking/rwsem.h +0 −23
lib/Kconfig.debug +4 −4

include/linux/rwsem.h+5−4

@@ -34,12 +34,12 @@ · 33 unmodified lines
34	34	*/
35	35	struct rw_semaphore {
36	36	atomic_long_t count;
37		−#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
38	37	/*
39		− * Write owner. Used as a speculative check to see
40		− * if the owner is running on the cpu.
	38	+ * Write owner or one of the read owners. Can be used as a
	39	+ * speculative check to see if the owner is running on the cpu.
41	40	*/
42	41	struct task_struct *owner;
	42	+#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
43	43	struct optimistic_spin_queue osq; /* spinner MCS lock */
44	44	#endif
45	45	raw_spinlock_t wait_lock;
@@ -73,13 +73,14 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem) · 27 unmodified lines
73	73	#endif
74	74
75	75	#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
76		−#define __RWSEM_OPT_INIT(lockname) , .osq = OSQ_LOCK_UNLOCKED, .owner = NULL
	76	+#define __RWSEM_OPT_INIT(lockname) , .osq = OSQ_LOCK_UNLOCKED
77	77	#else
78	78	#define __RWSEM_OPT_INIT(lockname)
79	79	#endif
80	80
81	81	#define __RWSEM_INITIALIZER(name) \
82	82	{ __RWSEM_INIT_COUNT(name), \
	83	+ .owner = NULL, \
83	84	.wait_list = LIST_HEAD_INIT((name).wait_list), \
84	85	.wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock) \
85	86	__RWSEM_OPT_INIT(name) \

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	}

lib/Kconfig.debug+4−4

@@ -1095,7 +1095,7 @@ config PROVE_LOCKING · 1094 unmodified lines
1095	1095	select DEBUG_SPINLOCK
1096	1096	select DEBUG_MUTEXES
1097	1097	select DEBUG_RT_MUTEXES if RT_MUTEXES
1098		− select DEBUG_RWSEMS if RWSEM_SPIN_ON_OWNER
	1098	+ select DEBUG_RWSEMS
1099	1099	select DEBUG_WW_MUTEX_SLOWPATH
1100	1100	select DEBUG_LOCK_ALLOC
1101	1101	select TRACE_IRQFLAGS
@@ -1199,10 +1199,10 @@ config DEBUG_WW_MUTEX_SLOWPATH · 97 unmodified lines
1199	1199
1200	1200	config DEBUG_RWSEMS
1201	1201	bool "RW Semaphore debugging: basic checks"
1202		− depends on DEBUG_KERNEL && RWSEM_SPIN_ON_OWNER
	1202	+ depends on DEBUG_KERNEL
1203	1203	help
1204		− This debugging feature allows mismatched rw semaphore locks and unlocks
1205		− to be detected and reported.
	1204	+ This debugging feature allows mismatched rw semaphore locks
	1205	+ and unlocks to be detected and reported.
1206	1206
1207	1207	config DEBUG_LOCK_ALLOC
1208	1208	bool "Lock debugging: detect incorrect freeing of live locks"