X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu-qsbr.h;h=346f906202aa60edc8f5c77628e18af5f130361a;hp=101b94d49d83c71230bf208bf5cd9771656bab5b;hb=4d1ce26fea0296ff67791c881836393fdd020cf9;hpb=420e5b9208a77041b662c9d9cdc021287f95eec1 diff --git a/urcu-qsbr.h b/urcu-qsbr.h index 101b94d..346f906 100644 --- a/urcu-qsbr.h +++ b/urcu-qsbr.h @@ -2,15 +2,14 @@ #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 - * Copyright (c) 2009 Paul E. McKenney, IBM Corporation. + * #define _LGPL_SOURCE + * #include * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public @@ -32,246 +31,91 @@ #include #include -#include -#include - -/* - * Identify a shared load. A smp_rmc() or smp_mc() should come before the load. - */ -#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); \ - }) - -/* - * Identify a shared store. A smp_wmc() or smp_mc() should follow the store. - */ -#define _STORE_SHARED(x, v) ({ ACCESS_ONCE(x) = (v); }) - -/* - * Store v into x, where x is located in shared memory. Performs the required - * cache flush after writing. Returns v. - */ -#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. + * Important ! * - * 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(). + * 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 = LOAD_SHARED(p); \ - smp_read_barrier_depends(); \ - (_________p1); \ - }) - -/* - * 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. - */ +#ifdef _LGPL_SOURCE -/* - * The signal number used by the RCU library can be overridden with - * -DSIGURCU= when compiling the library. - */ -#ifndef SIGURCU -#define SIGURCU SIGUSR1 -#endif +#include /* - * If a reader is really non-cooperative and refuses to commit its - * urcu_active_readers count to memory (there is no barrier in the reader - * per-se), kick it after a few loops waiting for it. + * Mappings for static use of the userspace RCU library. + * Should only be used in LGPL-compatible code. */ -#define KICK_READER_LOOPS 10000 - -#ifdef DEBUG_YIELD -#include -#include -#include -#include - -#define YIELD_READ (1 << 0) -#define YIELD_WRITE (1 << 1) - -/* Updates without DEBUG_FULL_MB are much slower. Account this in the delay */ -#ifdef DEBUG_FULL_MB -/* maximum sleep delay, in us */ -#define MAX_SLEEP 50 -#else -#define MAX_SLEEP 30000 -#endif - -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) - usleep(rand_r(&rand_yield) % MAX_SLEEP); -} - -static inline void debug_yield_write(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) -{ -} +#define rcu_dereference _rcu_dereference +#define rcu_read_lock _rcu_read_lock +#define rcu_read_unlock _rcu_read_unlock -static inline void debug_yield_write(void) -{ -} +#define rcu_quiescent_state _rcu_quiescent_state +#define rcu_thread_offline _rcu_thread_offline +#define rcu_thread_online _rcu_thread_online -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 - -#ifdef DEBUG_FULL_MB -static inline void reader_barrier() -{ - smp_mb(); -} -#else -static inline void reader_barrier() -{ - barrier(); -} -#endif +#else /* !_LGPL_SOURCE */ /* - * The trick here is that RCU_GP_CTR_BIT must be a multiple of 8 so we can use a - * full 8-bits, 16-bits or 32-bits bitmask for the lower order bits. + * library wrappers to be used by non-LGPL compatible source code. */ -#define RCU_GP_COUNT (1UL << 0) -/* Use the amount of bits equal to half of the architecture long size */ -#define RCU_GP_CTR_BIT (1UL << (sizeof(long) << 2)) -#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. + * 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. */ -extern long urcu_gp_ctr; -extern long __thread urcu_active_readers; +#if (!defined(BUILD_QSBR_LIB) && defined(URCU_DEBUG)) -static inline int rcu_old_gp_ongoing(long *value) +static inline void rcu_read_lock(void) { - if (value == NULL) - return 0; - - return LOAD_SHARED(*value) & 1; } -static inline void _rcu_read_lock(void) +static inline void rcu_read_lock(void) { } -static inline void _rcu_read_unlock(void) -{ -} +#else /* !URCU_DEBUG */ -static inline void _rcu_quiescent_state(void) -{ - smp_mb(); - urcu_active_readers = ACCESS_ONCE(urcu_gp_ctr) + 1; - smp_mb(); -} +extern void rcu_read_lock(void); +extern void rcu_read_unlock(void); -static inline void _rcu_thread_offline(void) -{ - smp_mb(); - urcu_active_readers = ACCESS_ONCE(urcu_gp_ctr); -} +#endif /* !URCU_DEBUG */ -static inline void _rcu_thread_online(void) -{ - urcu_active_readers = ACCESS_ONCE(urcu_gp_ctr) + 1; - smp_mb(); -} +extern void *rcu_dereference(void *p); -/** - * _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(). - */ +extern void rcu_quiescent_state(void); +extern void rcu_thread_offline(void); +extern void rcu_thread_online(void); -#define _rcu_assign_pointer(p, v) \ - ({ \ - if (!__builtin_constant_p(v) || \ - ((v) != NULL)) \ - wmb(); \ - STORE_SHARED(p, v); \ - }) +extern void *rcu_assign_pointer_sym(void **p, void *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_assign_pointer(p, v) \ + rcu_assign_pointer_sym((void **)(p), (v)) -#define _rcu_xchg_pointer(p, v) \ - ({ \ - if (!__builtin_constant_p(v) || \ - ((v) != NULL)) \ - wmb(); \ - xchg(p, v); \ - }) +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)) -/* - * 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; \ - }) +extern void *rcu_xchg_pointer_sym(void **p, void *v); +#define rcu_xchg_pointer(p, v) \ + rcu_xchg_pointer_sym((void **)(p), (v)) + +extern void *rcu_publish_content_sym(void **p, void *v); +#define rcu_publish_content(p, v) \ + rcu_publish_content_sym((void **)(p), (v)) + +#endif /* !_LGPL_SOURCE */ extern void synchronize_rcu(void);