Update Linux to v5.4.2
Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index ab93b6e..00d6054 100644
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -20,24 +20,33 @@
#include <linux/osq_lock.h>
#endif
-struct rw_semaphore;
-
-#ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
-#include <linux/rwsem-spinlock.h> /* use a generic implementation */
-#define __RWSEM_INIT_COUNT(name) .count = RWSEM_UNLOCKED_VALUE
-#else
-/* All arch specific implementations share the same struct */
+/*
+ * For an uncontended rwsem, count and owner are the only fields a task
+ * needs to touch when acquiring the rwsem. So they are put next to each
+ * other to increase the chance that they will share the same cacheline.
+ *
+ * In a contended rwsem, the owner is likely the most frequently accessed
+ * field in the structure as the optimistic waiter that holds the osq lock
+ * will spin on owner. For an embedded rwsem, other hot fields in the
+ * containing structure should be moved further away from the rwsem to
+ * reduce the chance that they will share the same cacheline causing
+ * cacheline bouncing problem.
+ */
struct rw_semaphore {
atomic_long_t count;
- struct list_head wait_list;
- raw_spinlock_t wait_lock;
+ /*
+ * Write owner or one of the read owners as well flags regarding
+ * the current state of the rwsem. Can be used as a speculative
+ * check to see if the write owner is running on the cpu.
+ */
+ atomic_long_t owner;
#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
struct optimistic_spin_queue osq; /* spinner MCS lock */
- /*
- * Write owner. Used as a speculative check to see
- * if the owner is running on the cpu.
- */
- struct task_struct *owner;
+#endif
+ raw_spinlock_t wait_lock;
+ struct list_head wait_list;
+#ifdef CONFIG_DEBUG_RWSEMS
+ void *magic;
#endif
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
@@ -45,20 +54,10 @@
};
/*
- * Setting bit 0 of the owner field with other non-zero bits will indicate
+ * Setting all bits of the owner field except bit 0 will indicate
* that the rwsem is writer-owned with an unknown owner.
*/
-#define RWSEM_OWNER_UNKNOWN ((struct task_struct *)-1L)
-
-extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
-extern struct rw_semaphore *rwsem_down_read_failed_killable(struct rw_semaphore *sem);
-extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
-extern struct rw_semaphore *rwsem_down_write_failed_killable(struct rw_semaphore *sem);
-extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *);
-extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
-
-/* Include the arch specific part */
-#include <asm/rwsem.h>
+#define RWSEM_OWNER_UNKNOWN (-2L)
/* In all implementations count != 0 means locked */
static inline int rwsem_is_locked(struct rw_semaphore *sem)
@@ -66,8 +65,8 @@
return atomic_long_read(&sem->count) != 0;
}
+#define RWSEM_UNLOCKED_VALUE 0L
#define __RWSEM_INIT_COUNT(name) .count = ATOMIC_LONG_INIT(RWSEM_UNLOCKED_VALUE)
-#endif
/* Common initializer macros and functions */
@@ -77,17 +76,25 @@
# define __RWSEM_DEP_MAP_INIT(lockname)
#endif
+#ifdef CONFIG_DEBUG_RWSEMS
+# define __DEBUG_RWSEM_INITIALIZER(lockname) , .magic = &lockname
+#else
+# define __DEBUG_RWSEM_INITIALIZER(lockname)
+#endif
+
#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
-#define __RWSEM_OPT_INIT(lockname) , .osq = OSQ_LOCK_UNLOCKED, .owner = NULL
+#define __RWSEM_OPT_INIT(lockname) , .osq = OSQ_LOCK_UNLOCKED
#else
#define __RWSEM_OPT_INIT(lockname)
#endif
#define __RWSEM_INITIALIZER(name) \
{ __RWSEM_INIT_COUNT(name), \
+ .owner = ATOMIC_LONG_INIT(0), \
.wait_list = LIST_HEAD_INIT((name).wait_list), \
.wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock) \
__RWSEM_OPT_INIT(name) \
+ __DEBUG_RWSEM_INITIALIZER(name) \
__RWSEM_DEP_MAP_INIT(name) }
#define DECLARE_RWSEM(name) \
@@ -163,7 +170,7 @@
* static then another method for expressing nested locking is
* the explicit definition of lock class keys and the use of
* lockdep_set_class() at lock initialization time.
- * See Documentation/locking/lockdep-design.txt for more details.)
+ * See Documentation/locking/lockdep-design.rst for more details.)
*/
extern void down_read_nested(struct rw_semaphore *sem, int subclass);
extern void down_write_nested(struct rw_semaphore *sem, int subclass);