* Distributed under GPLv2
*/
+#include <stdlib.h>
+
/* The "volatile" is due to gcc bugs */
#define barrier() __asm__ __volatile__("": : :"memory")
}
#endif
-/* Global quiescent period parity */
-extern int urcu_qparity;
+/*
+ * Limiting the nesting level to 256 to keep instructions small in the read
+ * fast-path.
+ */
+#define RCU_GP_COUNT (1U << 0)
+#define RCU_GP_CTR_BIT (1U << 8)
+#define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_BIT - 1)
+
+/* Global quiescent period counter with low-order bits unused. */
+extern int urcu_gp_ctr;
-extern int __thread urcu_active_readers[2];
+extern int __thread urcu_active_readers;
-static inline int get_urcu_qparity(void)
+static inline int rcu_old_gp_ongoing(int *value)
{
- return urcu_qparity;
+ int v;
+
+ if (value == NULL)
+ return 0;
+ debug_yield_write();
+ v = ACCESS_ONCE(*value);
+ debug_yield_write();
+ return (v & RCU_GP_CTR_NEST_MASK) &&
+ ((v ^ ACCESS_ONCE(urcu_gp_ctr)) & RCU_GP_CTR_BIT);
}
-/*
- * urcu_parity should be declared on the caller's stack.
- */
-static inline void rcu_read_lock(int *urcu_parity)
+static inline void rcu_read_lock(void)
{
+ int tmp;
+
debug_yield_read();
- *urcu_parity = get_urcu_qparity();
+ tmp = urcu_active_readers;
debug_yield_read();
- urcu_active_readers[*urcu_parity]++;
+ if (!(tmp & RCU_GP_CTR_NEST_MASK))
+ urcu_active_readers = urcu_gp_ctr + RCU_GP_COUNT;
+ else
+ urcu_active_readers = tmp + RCU_GP_COUNT;
debug_yield_read();
/*
* Increment active readers count before accessing the pointer.
debug_yield_read();
}
-static inline void rcu_read_unlock(int *urcu_parity)
+static inline void rcu_read_unlock(void)
{
debug_yield_read();
barrier();
* Finish using rcu before decrementing the pointer.
* See force_mb_all_threads().
*/
- urcu_active_readers[*urcu_parity]--;
+ urcu_active_readers -= RCU_GP_COUNT;
debug_yield_read();
}
+/**
+ * rcu_assign_pointer - assign (publicize) a pointer to a newly
+ * initialized structure that will be dereferenced by RCU read-side
+ * critical sections. Returns the value assigned.
+ *
+ * Inserts memory barriers on architectures that require them
+ * (pretty much all of them other than x86), and also prevents
+ * the compiler from reordering the code that initializes the
+ * structure after the pointer assignment. More importantly, this
+ * call documents which pointers will be dereferenced by RCU read-side
+ * code.
+ */
+
+#define rcu_assign_pointer(p, v) \
+ ({ \
+ if (!__builtin_constant_p(v) || \
+ ((v) != NULL)) \
+ wmb(); \
+ (p) = (v); \
+ })
+
extern void *urcu_publish_content(void **ptr, void *new);
+extern void synchronize_rcu(void);
/*
* Reader thread registration.