#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"
/* 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
+#ifdef DEBUG_YIELD
+#include <sched.h>
+
+#define YIELD_READ (1 << 0)
+#define YIELD_WRITE (1 << 1)
+
+extern unsigned int yield_active;
+extern unsigned int __thread rand_yield;
+
+static inline void debug_yield_read(void)
+{
+ if (yield_active & YIELD_READ)
+ if (rand_r(&rand_yield) & 0x1)
+ sched_yield();
+}
+
+static inline void debug_yield_write(void)
+{
+ if (yield_active & YIELD_WRITE)
+ if (rand_r(&rand_yield) & 0x1)
+ sched_yield();
+}
+
+static inline void debug_yield_init(void)
+{
+ rand_yield = time(NULL) ^ pthread_self();
+}
+#else
+static inline void debug_yield_read(void)
+{
+}
+
+static inline void debug_yield_write(void)
+{
+}
+
+static inline void debug_yield_init(void)
+{
+
+}
+#endif
+
/* Global quiescent period parity */
extern int urcu_qparity;
}
/*
- * returns urcu_parity.
+ * urcu_parity should be declared on the caller's stack.
*/
-static inline int rcu_read_lock(void)
+static inline void rcu_read_lock(int *urcu_parity)
{
- int urcu_parity = get_urcu_qparity();
- urcu_active_readers[urcu_parity]++;
+ debug_yield_read();
+ *urcu_parity = get_urcu_qparity();
+ debug_yield_read();
+ urcu_active_readers[*urcu_parity]++;
+ debug_yield_read();
/*
* Increment active readers count before accessing the pointer.
* See force_mb_all_threads().
*/
barrier();
- return urcu_parity;
+ debug_yield_read();
}
-static inline void rcu_read_unlock(int urcu_parity)
+static inline void rcu_read_unlock(int *urcu_parity)
{
+ debug_yield_read();
barrier();
+ debug_yield_read();
/*
* Finish using rcu before decrementing the pointer.
* See force_mb_all_threads().
*/
- urcu_active_readers[urcu_parity]--;
+ urcu_active_readers[*urcu_parity]--;
+ debug_yield_read();
}
extern void *urcu_publish_content(void **ptr, void *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 */