X-Git-Url: http://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=include%2Furcu%2Fstatic%2Furcu-bp.h;fp=include%2Furcu%2Fstatic%2Furcu-bp.h;h=6e52d84bafe84f75dfd45593a2b58cad6431bcd0;hp=0000000000000000000000000000000000000000;hb=6893800a4d1cc14dff0395ddcd660a5138db183d;hpb=a59f39055b5ecb77b68cf78b9839aa9e8e4ec332 diff --git a/include/urcu/static/urcu-bp.h b/include/urcu/static/urcu-bp.h new file mode 100644 index 0000000..6e52d84 --- /dev/null +++ b/include/urcu/static/urcu-bp.h @@ -0,0 +1,206 @@ +#ifndef _URCU_BP_STATIC_H +#define _URCU_BP_STATIC_H + +/* + * urcu-bp-static.h + * + * Userspace RCU header. + * + * TO BE INCLUDED ONLY IN CODE THAT IS TO BE RECOMPILED ON EACH LIBURCU + * RELEASE. See urcu.h for linking dynamically with the userspace rcu library. + * + * Copyright (c) 2009 Mathieu Desnoyers + * Copyright (c) 2009 Paul E. McKenney, IBM Corporation. + * + * 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. + */ + +#include +#include +#include + +#include +#include +#include +#include +#include +#include +#include + +/* + * 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 __cplusplus +extern "C" { +#endif + +enum rcu_state { + RCU_READER_ACTIVE_CURRENT, + RCU_READER_ACTIVE_OLD, + RCU_READER_INACTIVE, +}; + +/* + * The trick here is that RCU_GP_CTR_PHASE 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. + */ +#define RCU_GP_COUNT (1UL << 0) +/* Use the amount of bits equal to half of the architecture long size */ +#define RCU_GP_CTR_PHASE (1UL << (sizeof(long) << 2)) +#define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_PHASE - 1) + +/* + * Used internally by _rcu_read_lock. + */ +extern void rcu_bp_register(void); + +struct rcu_gp { + /* + * Global grace period counter. + * Contains the current RCU_GP_CTR_PHASE. + * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path. + * Written to only by writer with mutex taken. + * Read by both writer and readers. + */ + unsigned long ctr; +} __attribute__((aligned(CAA_CACHE_LINE_SIZE))); + +extern struct rcu_gp rcu_gp; + +struct rcu_reader { + /* Data used by both reader and synchronize_rcu() */ + unsigned long ctr; + /* Data used for registry */ + struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE))); + pthread_t tid; + int alloc; /* registry entry allocated */ +}; + +/* + * Bulletproof version keeps a pointer to a registry not part of the TLS. + * Adds a pointer dereference on the read-side, but won't require to unregister + * the reader thread. + */ +extern DECLARE_URCU_TLS(struct rcu_reader *, rcu_reader); + +extern int urcu_bp_has_sys_membarrier; + +static inline void urcu_bp_smp_mb_slave(void) +{ + if (caa_likely(urcu_bp_has_sys_membarrier)) + cmm_barrier(); + else + cmm_smp_mb(); +} + +static inline enum rcu_state rcu_reader_state(unsigned long *ctr) +{ + unsigned long v; + + if (ctr == NULL) + return RCU_READER_INACTIVE; + /* + * Make sure both tests below are done on the same version of *value + * to insure consistency. + */ + v = CMM_LOAD_SHARED(*ctr); + if (!(v & RCU_GP_CTR_NEST_MASK)) + return RCU_READER_INACTIVE; + if (!((v ^ rcu_gp.ctr) & RCU_GP_CTR_PHASE)) + return RCU_READER_ACTIVE_CURRENT; + return RCU_READER_ACTIVE_OLD; +} + +/* + * Helper for _rcu_read_lock(). The format of rcu_gp.ctr (as well as + * the per-thread rcu_reader.ctr) has the upper bits containing a count of + * _rcu_read_lock() nesting, and a lower-order bit that contains either zero + * or RCU_GP_CTR_PHASE. The smp_mb_slave() ensures that the accesses in + * _rcu_read_lock() happen before the subsequent read-side critical section. + */ +static inline void _rcu_read_lock_update(unsigned long tmp) +{ + if (caa_likely(!(tmp & RCU_GP_CTR_NEST_MASK))) { + _CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, _CMM_LOAD_SHARED(rcu_gp.ctr)); + urcu_bp_smp_mb_slave(); + } else + _CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, tmp + RCU_GP_COUNT); +} + +/* + * Enter an RCU read-side critical section. + * + * The first cmm_barrier() call ensures that the compiler does not reorder + * the body of _rcu_read_lock() with a mutex. + * + * This function and its helper are both less than 10 lines long. The + * intent is that this function meets the 10-line criterion in LGPL, + * allowing this function to be invoked directly from non-LGPL code. + */ +static inline void _rcu_read_lock(void) +{ + unsigned long tmp; + + if (caa_unlikely(!URCU_TLS(rcu_reader))) + rcu_bp_register(); /* If not yet registered. */ + cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */ + tmp = URCU_TLS(rcu_reader)->ctr; + urcu_assert((tmp & RCU_GP_CTR_NEST_MASK) != RCU_GP_CTR_NEST_MASK); + _rcu_read_lock_update(tmp); +} + +/* + * Exit an RCU read-side critical section. This function is less than + * 10 lines of code, and is intended to be usable by non-LGPL code, as + * called out in LGPL. + */ +static inline void _rcu_read_unlock(void) +{ + unsigned long tmp; + + tmp = URCU_TLS(rcu_reader)->ctr; + urcu_assert(tmp & RCU_GP_CTR_NEST_MASK); + /* Finish using rcu before decrementing the pointer. */ + urcu_bp_smp_mb_slave(); + _CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, tmp - RCU_GP_COUNT); + cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */ +} + +/* + * Returns whether within a RCU read-side critical section. + * + * This function is less than 10 lines long. The intent is that this + * function meets the 10-line criterion for LGPL, allowing this function + * to be invoked directly from non-LGPL code. + */ +static inline int _rcu_read_ongoing(void) +{ + if (caa_unlikely(!URCU_TLS(rcu_reader))) + rcu_bp_register(); /* If not yet registered. */ + return URCU_TLS(rcu_reader)->ctr & RCU_GP_CTR_NEST_MASK; +} + +#ifdef __cplusplus +} +#endif + +#endif /* _URCU_BP_STATIC_H */