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hc
2023-12-09 b22da3d8526a935aa31e086e63f60ff3246cb61c 
 kernel/include/linux/rwsem.h
....@@ -16,54 +16,63 @@
1616 #include <linux/spinlock.h>
1717 #include <linux/atomic.h>
1818 #include <linux/err.h>
19
+
20
+#ifdef CONFIG_PREEMPT_RT
21
+#include <linux/rwsem-rt.h>
22
+#else /* PREEMPT_RT */
23
+
1924 #ifdef CONFIG_RWSEM_SPIN_ON_OWNER
2025 #include <linux/osq_lock.h>
2126 #endif
27
+#include <linux/android_vendor.h>
2228 
23
-struct rw_semaphore;
24
-
25
-#ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
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-#include <linux/rwsem-spinlock.h> /* use a generic implementation */
27
-#define __RWSEM_INIT_COUNT(name)	.count = RWSEM_UNLOCKED_VALUE
28
-#else
29
-/* All arch specific implementations share the same struct */
29
+/*
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+ * For an uncontended rwsem, count and owner are the only fields a task
31
+ * needs to touch when acquiring the rwsem. So they are put next to each
32
+ * other to increase the chance that they will share the same cacheline.
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+ *
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+ * In a contended rwsem, the owner is likely the most frequently accessed
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+ * field in the structure as the optimistic waiter that holds the osq lock
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+ * will spin on owner. For an embedded rwsem, other hot fields in the
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+ * containing structure should be moved further away from the rwsem to
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+ * reduce the chance that they will share the same cacheline causing
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+ * cacheline bouncing problem.
40
+ */
3041 struct rw_semaphore {
3142 	atomic_long_t count;
32
-	struct list_head wait_list;
33
-	raw_spinlock_t wait_lock;
43
+	/*
44
+	 * Write owner or one of the read owners as well flags regarding
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+	 * the current state of the rwsem. Can be used as a speculative
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+	 * check to see if the write owner is running on the cpu.
47
+	 */
48
+	atomic_long_t owner;
3449 #ifdef CONFIG_RWSEM_SPIN_ON_OWNER
3550 	struct optimistic_spin_queue osq; /* spinner MCS lock */
36
-	/*
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-	 * Write owner. Used as a speculative check to see
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-	 * if the owner is running on the cpu.
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-	 */
40
-	struct task_struct *owner;
51
+#endif
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+	raw_spinlock_t wait_lock;
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+	struct list_head wait_list;
54
+#ifdef CONFIG_DEBUG_RWSEMS
55
+	void *magic;
4156 #endif
4257 #ifdef CONFIG_DEBUG_LOCK_ALLOC
4358 	struct lockdep_map	dep_map;
4459 #endif
45
-        /* NOTICE: m_count is a vendor variable used for the config
46
-         * CONFIG_RWSEM_PRIO_AWARE. This is included here to maintain ABI
47
-         * compatibility with our vendors */
48
-        /* count for waiters preempt to queue in wait list */
49
-	long m_count;
60
+	ANDROID_VENDOR_DATA(1);
61
+	ANDROID_OEM_DATA_ARRAY(1, 2);
5062 };
5163 
52
-/*
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- * Setting bit 0 of the owner field with other non-zero bits will indicate
54
- * that the rwsem is writer-owned with an unknown owner.
55
- */
56
-#define RWSEM_OWNER_UNKNOWN	((struct task_struct *)-1L)
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+enum rwsem_waiter_type {
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+	RWSEM_WAITING_FOR_WRITE,
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+	RWSEM_WAITING_FOR_READ
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+};
5768 
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-extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
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-extern struct rw_semaphore *rwsem_down_read_failed_killable(struct rw_semaphore *sem);
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-extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
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-extern struct rw_semaphore *rwsem_down_write_failed_killable(struct rw_semaphore *sem);
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-extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *);
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-extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
64
-
65
-/* Include the arch specific part */
66
-#include <asm/rwsem.h>
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+struct rwsem_waiter {
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+	struct list_head list;
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+	struct task_struct *task;
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+	enum rwsem_waiter_type type;
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+	unsigned long timeout;
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+	unsigned long last_rowner;
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+};
6776 
6877 /* In all implementations count != 0 means locked */
6978 static inline int rwsem_is_locked(struct rw_semaphore *sem)
....@@ -71,28 +80,40 @@
7180 	return atomic_long_read(&sem->count) != 0;
7281 }
7382 
74
-#define __RWSEM_INIT_COUNT(name)	.count = ATOMIC_LONG_INIT(RWSEM_UNLOCKED_VALUE)
75
-#endif
83
+#define RWSEM_UNLOCKED_VALUE		0L
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+#define __RWSEM_COUNT_INIT(name)	.count = ATOMIC_LONG_INIT(RWSEM_UNLOCKED_VALUE)
7685 
7786 /* Common initializer macros and functions */
7887 
7988 #ifdef CONFIG_DEBUG_LOCK_ALLOC
80
-# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
89
+# define __RWSEM_DEP_MAP_INIT(lockname)			\
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+	.dep_map = {					\
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+		.name = #lockname,			\
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+		.wait_type_inner = LD_WAIT_SLEEP,	\
93
+	},
8194 #else
8295 # define __RWSEM_DEP_MAP_INIT(lockname)
8396 #endif
8497 
98
+#ifdef CONFIG_DEBUG_RWSEMS
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+# define __RWSEM_DEBUG_INIT(lockname) .magic = &lockname,
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+#else
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+# define __RWSEM_DEBUG_INIT(lockname)
102
+#endif
103
+
85104 #ifdef CONFIG_RWSEM_SPIN_ON_OWNER
86
-#define __RWSEM_OPT_INIT(lockname) , .osq = OSQ_LOCK_UNLOCKED, .owner = NULL
105
+#define __RWSEM_OPT_INIT(lockname) .osq = OSQ_LOCK_UNLOCKED,
87106 #else
88107 #define __RWSEM_OPT_INIT(lockname)
89108 #endif
90109 
91110 #define __RWSEM_INITIALIZER(name)				\
92
-	{ __RWSEM_INIT_COUNT(name),				\
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-	  .wait_list = LIST_HEAD_INIT((name).wait_list),	\
94
-	  .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock)	\
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+	{ __RWSEM_COUNT_INIT(name),				\
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+	  .owner = ATOMIC_LONG_INIT(0),				\
95113 	  __RWSEM_OPT_INIT(name)				\
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+	  .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock),\
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+	  .wait_list = LIST_HEAD_INIT((name).wait_list),	\
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+	  __RWSEM_DEBUG_INIT(name)				\
96117 	  __RWSEM_DEP_MAP_INIT(name) }
97118 
98119 #define DECLARE_RWSEM(name) \
....@@ -119,10 +140,18 @@
119140 	return !list_empty(&sem->wait_list);
120141 }
121142 
143
+#endif /* !PREEMPT_RT */
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+
145
+/*
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+ * The functions below are the same for all rwsem implementations including
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+ * the RT specific variant.
148
+ */
149
+
122150 /*
123151  * lock for reading
124152  */
125153 extern void down_read(struct rw_semaphore *sem);
154
+extern int __must_check down_read_interruptible(struct rw_semaphore *sem);
126155 extern int __must_check down_read_killable(struct rw_semaphore *sem);
127156 
128157 /*
....@@ -168,9 +197,10 @@
168197  * static then another method for expressing nested locking is
169198  * the explicit definition of lock class keys and the use of
170199  * lockdep_set_class() at lock initialization time.
171
- * See Documentation/locking/lockdep-design.txt for more details.)
200
+ * See Documentation/locking/lockdep-design.rst for more details.)
172201  */
173202 extern void down_read_nested(struct rw_semaphore *sem, int subclass);
203
+extern int __must_check down_read_killable_nested(struct rw_semaphore *sem, int subclass);
174204 extern void down_write_nested(struct rw_semaphore *sem, int subclass);
175205 extern int down_write_killable_nested(struct rw_semaphore *sem, int subclass);
176206 extern void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest_lock);
....@@ -191,6 +221,7 @@
191221 extern void up_read_non_owner(struct rw_semaphore *sem);
192222 #else
193223 # define down_read_nested(sem, subclass)		down_read(sem)
224
+# define down_read_killable_nested(sem, subclass)	down_read_killable(sem)
194225 # define down_write_nest_lock(sem, nest_lock)	down_write(sem)
195226 # define down_write_nested(sem, subclass)	down_write(sem)
196227 # define down_write_killable_nested(sem, subclass)	down_write_killable(sem)