X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu.h;h=c6c54e7c7c3bcbc83d88b279e20ab35f64a0806f;hp=9431da547bfcc8245d07969de426ac33c7fe3d2d;hb=eaf2c3f4b9041d2a6a85d7f9e56f6014603367d4;hpb=cdcb92bbb9e54201e0982844e3ca9cb4fd9b31e5 diff --git a/urcu.h b/urcu.h index 9431da5..c6c54e7 100644 --- a/urcu.h +++ b/urcu.h @@ -6,110 +6,98 @@ * * Userspace RCU header * - * Copyright February 2009 - Mathieu Desnoyers + * Copyright (c) 2009 Mathieu Desnoyers + * Copyright (c) 2009 Paul E. McKenney, IBM Corporation. * - * Credits for Paul e. McKenney - * for inspiration coming from the Linux kernel RCU and rcu-preempt. + * LGPL-compatible code should include this header with : * - * The barrier, mb, rmb, wmb, atomic_inc, smp_read_barrier_depends, ACCESS_ONCE - * and rcu_dereference primitives come from the Linux kernel. + * #define _LGPL_SOURCE + * #include * - * Distributed under GPLv2 + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + * + * IBM's contributions to this file may be relicensed under LGPLv2 or later. */ -/* The "volatile" is due to gcc bugs */ -#define barrier() __asm__ __volatile__("": : :"memory") - -/* x86 32/64 specific */ -#define mb() asm volatile("mfence":::"memory") -#define rmb() asm volatile("lfence":::"memory") -#define wmb() asm volatile("sfence" ::: "memory") - -static inline void atomic_inc(int *v) -{ - asm volatile("lock; incl %0" - : "+m" (*v)); -} - -/* Nop everywhere except on alpha. */ -#define smp_read_barrier_depends() +#include +#include /* - * 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. + * See urcu-pointer.h and urcu-pointer-static.h for pointer publication headers. */ -#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x)) +#include + +#ifdef __cplusplus +extern "C" { +#endif -/** - * rcu_dereference - fetch an RCU-protected pointer in an - * RCU read-side critical section. This pointer may later - * be safely dereferenced. +/* + * Important ! * - * Inserts memory barriers on architectures that require them - * (currently only the Alpha), and, more importantly, documents - * exactly which pointers are protected by RCU. + * 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 rcu_dereference(p) ({ \ - typeof(p) _________p1 = ACCESS_ONCE(p); \ - smp_read_barrier_depends(); \ - (_________p1); \ - }) +#ifdef _LGPL_SOURCE -#define SIGURCU SIGUSR1 +#include -/* Global quiescent period parity */ -extern int urcu_qparity; +/* + * Mappings for static use of the userspace RCU library. + * Should only be used in LGPL-compatible code. + */ -extern int __thread urcu_active_readers[2]; +/* + * rcu_read_lock() + * rcu_read_unlock() + * + * Mark the beginning and end of a read-side critical section. + * DON'T FORGET TO USE RCU_REGISTER/UNREGISTER_THREAD() FOR EACH THREAD WITH + * READ-SIDE CRITICAL SECTION. + */ +#define rcu_read_lock() _rcu_read_lock() +#define rcu_read_unlock() _rcu_read_unlock() -static inline int get_urcu_qparity(void) -{ - return urcu_qparity; -} +#else /* !_LGPL_SOURCE */ /* - * returns urcu_parity. + * library wrappers to be used by non-LGPL compatible source code. + * See LGPL-only urcu-pointer-static.h for documentation. */ -static inline int rcu_read_lock(void) -{ - int urcu_parity = get_urcu_qparity(); - urcu_active_readers[urcu_parity]++; - /* - * Increment active readers count before accessing the pointer. - * See force_mb_all_threads(). - */ - barrier(); - return urcu_parity; -} -static inline void rcu_read_unlock(int urcu_parity) -{ - barrier(); - /* - * Finish using rcu before decrementing the pointer. - * See force_mb_all_threads(). - */ - urcu_active_readers[urcu_parity]--; -} +extern void rcu_read_lock(void); +extern void rcu_read_unlock(void); -extern void rcu_write_lock(void); -extern void rcu_write_unlock(void); +#endif /* !_LGPL_SOURCE */ -extern void *urcu_publish_content(void **ptr, void *new); +extern void synchronize_rcu(void); /* * Reader thread registration. */ -extern void urcu_register_thread(void); -extern void urcu_unregister_thread(void); +extern void rcu_register_thread(void); +extern void rcu_unregister_thread(void); + +/* + * Explicit rcu initialization, for "early" use within library constructors. + */ +extern void rcu_init(void); + +#ifdef __cplusplus +} +#endif #endif /* _URCU_H */