#include <linux/rwsem_compat.h>
typedef enum {
- RW_DRIVER = 2,
- RW_DEFAULT = 4
+ RW_DRIVER = 2,
+ RW_DEFAULT = 4,
+ RW_NOLOCKDEP = 5
} krw_type_t;
typedef enum {
- RW_NONE = 0,
- RW_WRITER = 1,
- RW_READER = 2
+ RW_NONE = 0,
+ RW_WRITER = 1,
+ RW_READER = 2
} krw_t;
+/*
+ * If CONFIG_RWSEM_SPIN_ON_OWNER is defined, rw_semaphore will have an owner
+ * field, so we don't need our own.
+ */
typedef struct {
- struct rw_semaphore rw_rwlock;
- kthread_t *rw_owner;
+ struct rw_semaphore rw_rwlock;
+#ifndef CONFIG_RWSEM_SPIN_ON_OWNER
+ kthread_t *rw_owner;
+#endif
+#ifdef CONFIG_LOCKDEP
+ krw_type_t rw_type;
+#endif /* CONFIG_LOCKDEP */
} krwlock_t;
-#define SEM(rwp) ((struct rw_semaphore *)(rwp))
+#define SEM(rwp) (&(rwp)->rw_rwlock)
static inline void
spl_rw_set_owner(krwlock_t *rwp)
{
- unsigned long flags;
-
- spl_rwsem_lock_irqsave(&SEM(rwp)->wait_lock, flags);
- rwp->rw_owner = current;
- spl_rwsem_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
+/*
+ * If CONFIG_RWSEM_SPIN_ON_OWNER is defined, down_write, up_write,
+ * downgrade_write and __init_rwsem will set/clear owner for us.
+ */
+#ifndef CONFIG_RWSEM_SPIN_ON_OWNER
+ rwp->rw_owner = current;
+#endif
}
static inline void
spl_rw_clear_owner(krwlock_t *rwp)
{
- unsigned long flags;
-
- spl_rwsem_lock_irqsave(&SEM(rwp)->wait_lock, flags);
- rwp->rw_owner = NULL;
- spl_rwsem_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
+#ifndef CONFIG_RWSEM_SPIN_ON_OWNER
+ rwp->rw_owner = NULL;
+#endif
}
static inline kthread_t *
rw_owner(krwlock_t *rwp)
{
- unsigned long flags;
- kthread_t *owner;
-
- spl_rwsem_lock_irqsave(&SEM(rwp)->wait_lock, flags);
- owner = rwp->rw_owner;
- spl_rwsem_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
+#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
+ return SEM(rwp)->owner;
+#else
+ return rwp->rw_owner;
+#endif
+}
- return owner;
+#ifdef CONFIG_LOCKDEP
+static inline void
+spl_rw_set_type(krwlock_t *rwp, krw_type_t type)
+{
+ rwp->rw_type = type;
+}
+static inline void
+spl_rw_lockdep_off_maybe(krwlock_t *rwp) \
+{ \
+ if (rwp && rwp->rw_type == RW_NOLOCKDEP) \
+ lockdep_off(); \
+}
+static inline void
+spl_rw_lockdep_on_maybe(krwlock_t *rwp) \
+{ \
+ if (rwp && rwp->rw_type == RW_NOLOCKDEP) \
+ lockdep_on(); \
}
+#else /* CONFIG_LOCKDEP */
+#define spl_rw_set_type(rwp, type)
+#define spl_rw_lockdep_off_maybe(rwp)
+#define spl_rw_lockdep_on_maybe(rwp)
+#endif /* CONFIG_LOCKDEP */
static inline int
RW_READ_HELD(krwlock_t *rwp)
{
- return (spl_rwsem_is_locked(SEM(rwp)) &&
- rw_owner(rwp) == NULL);
+ return (spl_rwsem_is_locked(SEM(rwp)) && rw_owner(rwp) == NULL);
}
static inline int
RW_WRITE_HELD(krwlock_t *rwp)
{
- return (spl_rwsem_is_locked(SEM(rwp)) &&
- rw_owner(rwp) == current);
+ return (rw_owner(rwp) == current);
}
static inline int
* will be correctly located in the users code which is important
* for the built in kernel lock analysis tools
*/
-#define rw_init(rwp, name, type, arg) \
-({ \
- static struct lock_class_key __key; \
- \
- __init_rwsem(SEM(rwp), #rwp, &__key); \
- spl_rw_clear_owner(rwp); \
+#define rw_init(rwp, name, type, arg) \
+({ \
+ static struct lock_class_key __key; \
+ ASSERT(type == RW_DEFAULT || type == RW_NOLOCKDEP); \
+ \
+ __init_rwsem(SEM(rwp), #rwp, &__key); \
+ spl_rw_clear_owner(rwp); \
+ spl_rw_set_type(rwp, type); \
})
-#define rw_destroy(rwp) \
-({ \
- VERIFY(!RW_LOCK_HELD(rwp)); \
+#define rw_destroy(rwp) \
+({ \
+ VERIFY(!RW_LOCK_HELD(rwp)); \
})
-#define rw_tryenter(rwp, rw) \
-({ \
- int _rc_ = 0; \
- \
- switch (rw) { \
- case RW_READER: \
- _rc_ = down_read_trylock(SEM(rwp)); \
- break; \
- case RW_WRITER: \
- if ((_rc_ = down_write_trylock(SEM(rwp)))) \
- spl_rw_set_owner(rwp); \
- break; \
- default: \
- VERIFY(0); \
- } \
- _rc_; \
+#define rw_tryenter(rwp, rw) \
+({ \
+ int _rc_ = 0; \
+ \
+ spl_rw_lockdep_off_maybe(rwp); \
+ switch (rw) { \
+ case RW_READER: \
+ _rc_ = down_read_trylock(SEM(rwp)); \
+ break; \
+ case RW_WRITER: \
+ if ((_rc_ = down_write_trylock(SEM(rwp)))) \
+ spl_rw_set_owner(rwp); \
+ break; \
+ default: \
+ VERIFY(0); \
+ } \
+ spl_rw_lockdep_on_maybe(rwp); \
+ _rc_; \
})
-#define rw_enter(rwp, rw) \
-({ \
- switch (rw) { \
- case RW_READER: \
- down_read(SEM(rwp)); \
- break; \
- case RW_WRITER: \
- down_write(SEM(rwp)); \
- spl_rw_set_owner(rwp); \
- break; \
- default: \
- VERIFY(0); \
- } \
+#define rw_enter(rwp, rw) \
+({ \
+ spl_rw_lockdep_off_maybe(rwp); \
+ switch (rw) { \
+ case RW_READER: \
+ down_read(SEM(rwp)); \
+ break; \
+ case RW_WRITER: \
+ down_write(SEM(rwp)); \
+ spl_rw_set_owner(rwp); \
+ break; \
+ default: \
+ VERIFY(0); \
+ } \
+ spl_rw_lockdep_on_maybe(rwp); \
})
-#define rw_exit(rwp) \
-({ \
- if (RW_WRITE_HELD(rwp)) { \
- spl_rw_clear_owner(rwp); \
- up_write(SEM(rwp)); \
- } else { \
- ASSERT(RW_READ_HELD(rwp)); \
- up_read(SEM(rwp)); \
- } \
+#define rw_exit(rwp) \
+({ \
+ spl_rw_lockdep_off_maybe(rwp); \
+ if (RW_WRITE_HELD(rwp)) { \
+ spl_rw_clear_owner(rwp); \
+ up_write(SEM(rwp)); \
+ } else { \
+ ASSERT(RW_READ_HELD(rwp)); \
+ up_read(SEM(rwp)); \
+ } \
+ spl_rw_lockdep_on_maybe(rwp); \
})
-#define rw_downgrade(rwp) \
-({ \
- spl_rw_clear_owner(rwp); \
- downgrade_write(SEM(rwp)); \
+#define rw_downgrade(rwp) \
+({ \
+ spl_rw_lockdep_off_maybe(rwp); \
+ spl_rw_clear_owner(rwp); \
+ downgrade_write(SEM(rwp)); \
+ spl_rw_lockdep_on_maybe(rwp); \
})
-#if defined(CONFIG_RWSEM_GENERIC_SPINLOCK)
/*
- * For the generic implementations of rw-semaphores the following is
- * true. If your semaphore implementation internally represents the
- * semaphore state differently then special case handling is required.
- * - if activity/count is 0 then there are no active readers or writers
- * - if activity/count is +ve then that is the number of active readers
- * - if activity/count is -1 then there is one active writer
+ * This implementation of rw_tryupgrade() behaves slightly differently
+ * from its counterparts on other platforms. It drops the RW_READER lock
+ * and then acquires the RW_WRITER lock leaving a small window where no
+ * lock is held. On other platforms the lock is never released during
+ * the upgrade process. This is necessary under Linux because the kernel
+ * does not provide an upgrade function.
*/
-
-extern void __up_read_locked(struct rw_semaphore *);
-extern int __down_write_trylock_locked(struct rw_semaphore *);
-
-#define rw_tryupgrade(rwp) \
-({ \
- unsigned long _flags_; \
- int _rc_ = 0; \
- \
- spl_rwsem_lock_irqsave(&SEM(rwp)->wait_lock, _flags_); \
- if ((list_empty(&SEM(rwp)->wait_list)) && \
- (SEM(rwp)->activity == 1)) { \
- __up_read_locked(SEM(rwp)); \
- VERIFY(_rc_ = __down_write_trylock_locked(SEM(rwp))); \
- (rwp)->rw_owner = current; \
- } \
- spl_rwsem_unlock_irqrestore(&SEM(rwp)->wait_lock, _flags_); \
- _rc_; \
+#define rw_tryupgrade(rwp) \
+({ \
+ int _rc_ = 0; \
+ \
+ if (RW_WRITE_HELD(rwp)) { \
+ _rc_ = 1; \
+ } else { \
+ spl_rw_lockdep_off_maybe(rwp); \
+ if ((_rc_ = rwsem_tryupgrade(SEM(rwp)))) \
+ spl_rw_set_owner(rwp); \
+ spl_rw_lockdep_on_maybe(rwp); \
+ } \
+ _rc_; \
})
-#else
-/*
- * rw_tryupgrade() can be implemented correctly but for each supported
- * arch we will need a custom implementation. For the x86 implementation
- * it looks like a custom cmpxchg() to atomically check and promote the
- * rwsem would be safe. For now that's not worth the trouble so in this
- * case rw_tryupgrade() has just been disabled.
- */
-#define rw_tryupgrade(rwp) ({ 0; })
-#endif
int spl_rw_init(void);
void spl_rw_fini(void);
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