#ifndef _URCU_H
#define _URCU_H
+/*
+ * urcu.h
+ *
+ * Userspace RCU header
+ *
+ * Copyright February 2009 - Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
+ *
+ * Credits for Paul e. McKenney <paulmck@linux.vnet.ibm.com>
+ * for inspiration coming from the Linux kernel RCU and rcu-preempt.
+ *
+ * The barrier, mb, rmb, wmb, atomic_inc, smp_read_barrier_depends, ACCESS_ONCE
+ * and rcu_dereference primitives come from the Linux kernel.
+ *
+ * Distributed under GPLv2
+ */
+
/* The "volatile" is due to gcc bugs */
#define barrier() __asm__ __volatile__("": : :"memory")
#define rmb() asm volatile("lfence":::"memory")
#define wmb() asm volatile("sfence" ::: "memory")
-
-
-/* x86 32 */
static inline void atomic_inc(int *v)
{
asm volatile("lock; incl %0"
- : "+m" (v->counter));
+ : "+m" (*v));
}
/* Nop everywhere except on alpha. */
#define smp_read_barrier_depends()
+/*
+ * Prevent the compiler from merging or refetching accesses. The compiler
+ * is also forbidden from reordering successive instances of ACCESS_ONCE(),
+ * but only when the compiler is aware of some particular ordering. One way
+ * to make the compiler aware of ordering is to put the two invocations of
+ * ACCESS_ONCE() in different C statements.
+ *
+ * This macro does absolutely -nothing- to prevent the CPU from reordering,
+ * merging, or refetching absolutely anything at any time. Its main intended
+ * use is to mediate communication between process-level code and irq/NMI
+ * handlers, all running on the same CPU.
+ */
+#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
+
+/**
+ * rcu_dereference - fetch an RCU-protected pointer in an
+ * RCU read-side critical section. This pointer may later
+ * be safely dereferenced.
+ *
+ * Inserts memory barriers on architectures that require them
+ * (currently only the Alpha), and, more importantly, documents
+ * exactly which pointers are protected by RCU.
+ */
+
+#define rcu_dereference(p) ({ \
+ typeof(p) _________p1 = ACCESS_ONCE(p); \
+ smp_read_barrier_depends(); \
+ (_________p1); \
+ })
+
#define SIGURCU SIGUSR1
/* Global quiescent period parity */
urcu_active_readers[urcu_parity]--;
}
-extern void *urcu_publish_content(void **ptr, void *new);
+extern void rcu_write_lock(void);
+extern void rcu_write_unlock(void);
+
+extern void *_urcu_publish_content(void **ptr, void *new);
+
+/*
+ * gcc does not like automatic &struct ... * -> void **.
+ * Remove the warning. (hopefully this is ok)
+ */
+#define urcu_publish_content(ptr, new) _urcu_publish_content((void **)ptr, new)
/*
* Reader thread registration.
*/
extern void urcu_register_thread(void);
-extern void urcu_register_thread(void);
+extern void urcu_unregister_thread(void);
#endif /* _URCU_H */