X-Git-Url: http://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu.h;h=af7d75cb7bc9e389ba9896a9207695d4feea9540;hp=7c94a776119245086fc6a5ea84cd35684e0b2d8f;hb=7abf2d0da3b328572a17c9457b33c3890b0ba58b;hpb=5b1da0c8bb5fd8f6afd2ca821606cfe3aae838bd diff --git a/urcu.h b/urcu.h index 7c94a77..af7d75c 100644 --- a/urcu.h +++ b/urcu.h @@ -6,272 +6,91 @@ * * 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. */ -#define __USE_GNU #include - -/* The "volatile" is due to gcc bugs */ -#define barrier() __asm__ __volatile__("": : :"memory") - -#define likely(x) __builtin_expect(!!(x), 1) -#define unlikely(x) __builtin_expect(!!(x), 0) - -/* 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)); -} - -#define xchg(ptr, v) \ - ((__typeof__(*(ptr)))__xchg((unsigned long)(v), (ptr), sizeof(*(ptr)))) - -struct __xchg_dummy { - unsigned long a[100]; -}; -#define __xg(x) ((struct __xchg_dummy *)(x)) - -/* - * Note: no "lock" prefix even on SMP: xchg always implies lock anyway - * Note 2: xchg has side effect, so that attribute volatile is necessary, - * but generally the primitive is invalid, *ptr is output argument. --ANK - */ -static inline unsigned long __xchg(unsigned long x, volatile void *ptr, - int size) -{ - switch (size) { - case 1: - asm volatile("xchgb %b0,%1" - : "=q" (x) - : "m" (*__xg(ptr)), "0" (x) - : "memory"); - break; - case 2: - asm volatile("xchgw %w0,%1" - : "=r" (x) - : "m" (*__xg(ptr)), "0" (x) - : "memory"); - break; - case 4: - asm volatile("xchgl %k0,%1" - : "=r" (x) - : "m" (*__xg(ptr)), "0" (x) - : "memory"); - break; - case 8: - asm volatile("xchgq %0,%1" - : "=r" (x) - : "m" (*__xg(ptr)), "0" (x) - : "memory"); - break; - } - return x; -} - -/* Nop everywhere except on alpha. */ -#define smp_read_barrier_depends() +#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. + * Important ! * - * 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. + * 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 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. - */ +#ifdef _LGPL_SOURCE -#define rcu_dereference(p) ({ \ - typeof(p) _________p1 = ACCESS_ONCE(p); \ - smp_read_barrier_depends(); \ - (_________p1); \ - }) +#include -#define SIGURCU SIGUSR1 - -#ifdef DEBUG_YIELD -#include -#include -#include - -#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) -{ -} +/* + * Mappings for static use of the userspace RCU library. + * Should only be used in LGPL-compatible code. + */ -static inline void debug_yield_write(void) -{ -} +#define rcu_dereference _rcu_dereference +#define rcu_read_lock _rcu_read_lock +#define rcu_read_unlock _rcu_read_unlock -static inline void debug_yield_init(void) -{ +#define rcu_assign_pointer _rcu_assign_pointer +#define rcu_xchg_pointer _rcu_xchg_pointer +#define rcu_publish_content _rcu_publish_content -} -#endif +#else /* !_LGPL_SOURCE */ /* - * Limiting the nesting level to 256 to keep instructions small in the read - * fast-path. + * library wrappers to be used by non-LGPL compatible source code. */ -#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. - * Using a int rather than a char to eliminate false register dependencies - * causing stalls on some architectures. - */ -extern int urcu_gp_ctr; +extern void rcu_read_lock(void); +extern void rcu_read_unlock(void); -extern int __thread urcu_active_readers; +extern void *rcu_dereference(void *p); -static inline int rcu_old_gp_ongoing(int *value) -{ - int v; +extern void *rcu_assign_pointer_sym(void **p, void *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); -} +#define rcu_assign_pointer(p, v) \ + rcu_assign_pointer_sym((void **)(p), (v)) -static inline void rcu_read_lock(void) -{ - int tmp; +extern void *rcu_xchg_pointer_sym(void **p, void *v); +#define rcu_xchg_pointer(p, v) \ + rcu_xchg_pointer_sym((void **)(p), (v)) - debug_yield_read(); - tmp = urcu_active_readers; - debug_yield_read(); - if (likely(!(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. - * See force_mb_all_threads(). - */ - barrier(); - debug_yield_read(); -} +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_read_unlock(void) -{ - debug_yield_read(); - barrier(); - debug_yield_read(); - /* - * Finish using rcu before decrementing the pointer. - * See force_mb_all_threads(). - */ - 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); \ - }) - -#define rcu_xchg_pointer(p, v) \ - ({ \ - if (!__builtin_constant_p(v) || \ - ((v) != NULL)) \ - wmb(); \ - xchg(p, v); \ - }) +#endif /* !_LGPL_SOURCE */ extern void synchronize_rcu(void); -/* - * Exchanges the pointer and waits for quiescent state. - * The pointer returned can be freed. - */ -#define urcu_publish_content(p, v) \ - ({ \ - void *oldptr; \ - debug_yield_write(); \ - oldptr = rcu_xchg_pointer(p, v); \ - synchronize_rcu(); \ - oldptr; \ - }) - /* * 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); #endif /* _URCU_H */