#define _URCU_QSBR_H
/*
- * urcu-static.h
+ * urcu-qsbr.h
*
- * Userspace RCU header.
+ * Userspace RCU QSBR header.
*
- * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu.h for linking
- * dynamically with the userspace rcu library.
+ * LGPL-compatible code should include this header with :
*
- * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
- * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
+ * #define _LGPL_SOURCE
+ * #include <urcu.h>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
#include <stdlib.h>
#include <pthread.h>
-#include <compiler.h>
-#include <arch.h>
-
/*
- * Identify a shared load. A smp_rmc() or smp_mc() should come before the load.
+ * Important !
+ *
+ * Each thread containing read-side critical sections must be registered
+ * with rcu_register_thread() before calling rcu_read_lock().
+ * rcu_unregister_thread() should be called before the thread exits.
*/
-#define _LOAD_SHARED(p) ACCESS_ONCE(p)
-/*
- * Load a data from shared memory, doing a cache flush if required.
- */
-#define LOAD_SHARED(p) \
- ({ \
- smp_rmc(); \
- _LOAD_SHARED(p); \
- })
+#ifdef _LGPL_SOURCE
-/*
- * Identify a shared store. A smp_wmc() or smp_mc() should follow the store.
- */
-#define _STORE_SHARED(x, v) ({ ACCESS_ONCE(x) = (v); })
+#include <urcu-qsbr-static.h>
/*
- * Store v into x, where x is located in shared memory. Performs the required
- * cache flush after writing. Returns v.
+ * Mappings for static use of the userspace RCU library.
+ * Should only be used in LGPL-compatible code.
*/
-#define STORE_SHARED(x, v) \
- ({ \
- _STORE_SHARED(x, v); \
- smp_wmc(); \
- (v); \
- })
-/**
- * _rcu_dereference - reads (copy) a RCU-protected pointer to a local variable
- * into a RCU read-side critical section. The pointer can later be safely
- * dereferenced within the critical section.
- *
- * This ensures that the pointer copy is invariant thorough the whole critical
- * section.
- *
- * Inserts memory barriers on architectures that require them (currently only
- * Alpha) and documents which pointers are protected by RCU.
- *
- * Should match rcu_assign_pointer() or rcu_xchg_pointer().
- */
+#define rcu_dereference _rcu_dereference
+#define rcu_read_lock _rcu_read_lock
+#define rcu_read_unlock _rcu_read_unlock
-#define _rcu_dereference(p) ({ \
- typeof(p) _________p1 = LOAD_SHARED(p); \
- smp_read_barrier_depends(); \
- (_________p1); \
- })
+#define rcu_quiescent_state _rcu_quiescent_state
+#define rcu_thread_offline _rcu_thread_offline
+#define rcu_thread_online _rcu_thread_online
-/*
- * This code section can only be included in LGPL 2.1 compatible source code.
- * See below for the function call wrappers which can be used in code meant to
- * be only linked with the Userspace RCU library. This comes with a small
- * performance degradation on the read-side due to the added function calls.
- * This is required to permit relinking with newer versions of the library.
- */
+#define rcu_assign_pointer _rcu_assign_pointer
+#define rcu_xchg_pointer _rcu_xchg_pointer
+#define rcu_publish_content _rcu_publish_content
+
+#else /* !_LGPL_SOURCE */
/*
- * The signal number used by the RCU library can be overridden with
- * -DSIGURCU= when compiling the library.
+ * library wrappers to be used by non-LGPL compatible source code.
*/
-#ifndef SIGURCU
-#define SIGURCU SIGUSR1
-#endif
/*
- * If a reader is really non-cooperative and refuses to commit its
- * rcu_reader_qs_gp count to memory (there is no barrier in the reader
- * per-se), kick it after a few loops waiting for it.
+ * QSBR read lock/unlock are guaranteed to be no-ops. Therefore, we expose them
+ * in the LGPL header for any code to use. However, the debug version is not
+ * nops and may contain sanity checks. To activate it, applications must be
+ * recompiled with -DURCU_DEBUG (even non-LGPL/GPL applications). This is the
+ * best trade-off between license/performance/code triviality and
+ * library debugging & tracing features we could come up with.
*/
-#define KICK_READER_LOOPS 10000
-
-#ifdef DEBUG_YIELD
-#include <sched.h>
-#include <time.h>
-#include <pthread.h>
-#include <unistd.h>
-
-#define YIELD_READ (1 << 0)
-#define YIELD_WRITE (1 << 1)
-/* maximum sleep delay, in us */
-#define MAX_SLEEP 50
+#if (!defined(BUILD_QSBR_LIB) && defined(URCU_DEBUG))
-extern unsigned int yield_active;
-extern unsigned int __thread rand_yield;
-
-static inline void debug_yield_read(void)
+static inline void rcu_read_lock(void)
{
- if (yield_active & YIELD_READ)
- if (rand_r(&rand_yield) & 0x1)
- usleep(rand_r(&rand_yield) % MAX_SLEEP);
}
-static inline void debug_yield_write(void)
+static inline void rcu_read_lock(void)
{
- if (yield_active & YIELD_WRITE)
- if (rand_r(&rand_yield) & 0x1)
- usleep(rand_r(&rand_yield) % MAX_SLEEP);
}
-static inline void debug_yield_init(void)
-{
- rand_yield = time(NULL) ^ pthread_self();
-}
-#else
-static inline void debug_yield_read(void)
-{
-}
+#else /* !URCU_DEBUG */
-static inline void debug_yield_write(void)
-{
-}
+extern void rcu_read_lock(void);
+extern void rcu_read_unlock(void);
-static inline void debug_yield_init(void)
-{
+#endif /* !URCU_DEBUG */
-}
-#endif
+extern void *rcu_dereference(void *p);
-static inline void reader_barrier()
-{
- smp_mb();
-}
+extern void rcu_quiescent_state(void);
+extern void rcu_thread_offline(void);
+extern void rcu_thread_online(void);
-/*
- * Global quiescent period counter with low-order bits unused.
- * Using a int rather than a char to eliminate false register dependencies
- * causing stalls on some architectures.
- */
-extern long urcu_gp_ctr;
-
-extern long __thread rcu_reader_qs_gp;
-
-static inline int rcu_gp_ongoing(long *value)
-{
- if (value == NULL)
- return 0;
+extern void *rcu_assign_pointer_sym(void **p, void *v);
- return LOAD_SHARED(*value) & 1;
-}
-
-static inline void _rcu_read_lock(void)
-{
-}
+#define rcu_assign_pointer(p, v) \
+ rcu_assign_pointer_sym((void **)(p), (v))
-static inline void _rcu_read_unlock(void)
-{
-}
+extern void *rcu_cmpxchg_pointer_sym(void **p, void *old, void *_new);
+#define rcu_cmpxchg_pointer(p, old, _new) \
+ rcu_cmpxchg_pointer_sym((void **)(p), (old), (_new))
-static inline void _rcu_quiescent_state(void)
-{
- smp_mb();
- rcu_reader_qs_gp = ACCESS_ONCE(urcu_gp_ctr) + 1;
- smp_mb();
-}
+extern void *rcu_xchg_pointer_sym(void **p, void *v);
+#define rcu_xchg_pointer(p, v) \
+ rcu_xchg_pointer_sym((void **)(p), (v))
-static inline void _rcu_thread_offline(void)
-{
- smp_mb();
- rcu_reader_qs_gp = ACCESS_ONCE(urcu_gp_ctr);
-}
+extern void *rcu_publish_content_sym(void **p, void *v);
+#define rcu_publish_content(p, v) \
+ rcu_publish_content_sym((void **)(p), (v))
-static inline void _rcu_thread_online(void)
-{
- rcu_reader_qs_gp = ACCESS_ONCE(urcu_gp_ctr) + 1;
- smp_mb();
-}
-
-/**
- * _rcu_assign_pointer - assign (publicize) a pointer to a new data structure
- * meant to be read by RCU read-side critical sections. Returns the assigned
- * value.
- *
- * Documents which pointers will be dereferenced by RCU read-side critical
- * sections and adds the required memory barriers on architectures requiring
- * them. It also makes sure the compiler does not reorder code initializing the
- * data structure before its publication.
- *
- * Should match rcu_dereference_pointer().
- */
-
-#define _rcu_assign_pointer(p, v) \
- ({ \
- if (!__builtin_constant_p(v) || \
- ((v) != NULL)) \
- wmb(); \
- STORE_SHARED(p, v); \
- })
-
-/**
- * _rcu_xchg_pointer - same as rcu_assign_pointer, but returns the previous
- * pointer to the data structure, which can be safely freed after waiting for a
- * quiescent state using synchronize_rcu().
- */
-
-#define _rcu_xchg_pointer(p, v) \
- ({ \
- if (!__builtin_constant_p(v) || \
- ((v) != NULL)) \
- wmb(); \
- xchg(p, v); \
- })
-
-/*
- * Exchanges the pointer and waits for quiescent state.
- * The pointer returned can be freed.
- */
-#define _rcu_publish_content(p, v) \
- ({ \
- void *oldptr; \
- oldptr = _rcu_xchg_pointer(p, v); \
- synchronize_rcu(); \
- oldptr; \
- })
+#endif /* !_LGPL_SOURCE */
extern void synchronize_rcu(void);
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