X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu-bp-static.h;fp=urcu-bp-static.h;h=428c53f9d38cd6491d64926332498871f00df1a7;hp=0000000000000000000000000000000000000000;hb=fdee2e6dc73cc504ba24be89da539c68742e508e;hpb=f83e795f70708d3692542ac61a0cbb7a2b38fae7 diff --git a/urcu-bp-static.h b/urcu-bp-static.h new file mode 100644 index 0000000..428c53f --- /dev/null +++ b/urcu-bp-static.h @@ -0,0 +1,197 @@ +#ifndef _URCU_BP_STATIC_H +#define _URCU_BP_STATIC_H + +/* + * urcu-bp-static.h + * + * Userspace RCU header. + * + * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. 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 + +/* + * 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. + */ + +/* + * Active attempts to check for reader Q.S. before calling sleep(). + */ +#define RCU_QS_ACTIVE_ATTEMPTS 100 + +#ifdef DEBUG_RCU +#define rcu_assert(args...) assert(args) +#else +#define rcu_assert(args...) +#endif + +#ifdef DEBUG_YIELD +#include +#include +#include +#include + +#define YIELD_READ (1 << 0) +#define YIELD_WRITE (1 << 1) + +/* + * Updates without URCU_MB are much slower. Account this in + * the delay. + */ +/* maximum sleep delay, in us */ +#define MAX_SLEEP 50 + +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) +{ +} + +static inline void debug_yield_write(void) +{ +} + +static inline void debug_yield_init(void) +{ + +} +#endif + +/* + * 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. + */ +#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) + +/* + * Used internally by _rcu_read_lock. + */ +extern void rcu_bp_register(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; + +struct urcu_reader { + /* Data used by both reader and synchronize_rcu() */ + long ctr; + /* Data used for registry */ + struct list_head head __attribute__((aligned(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 struct urcu_reader __thread *urcu_reader; + +static inline int rcu_old_gp_ongoing(long *value) +{ + long v; + + if (value == NULL) + return 0; + /* + * Make sure both tests below are done on the same version of *value + * to insure consistency. + */ + v = LOAD_SHARED(*value); + return (v & RCU_GP_CTR_NEST_MASK) && + ((v ^ urcu_gp_ctr) & RCU_GP_CTR_BIT); +} + +static inline void _rcu_read_lock(void) +{ + long tmp; + + /* Check if registered */ + if (unlikely(!urcu_reader)) + rcu_bp_register(); + + tmp = urcu_reader->ctr; + /* urcu_gp_ctr = RCU_GP_COUNT | (~RCU_GP_CTR_BIT or RCU_GP_CTR_BIT) */ + if (likely(!(tmp & RCU_GP_CTR_NEST_MASK))) { + _STORE_SHARED(urcu_reader->ctr, _LOAD_SHARED(urcu_gp_ctr)); + /* + * Set active readers count for outermost nesting level before + * accessing the pointer. + */ + smp_mb(); + } else { + _STORE_SHARED(urcu_reader->ctr, tmp + RCU_GP_COUNT); + } +} + +static inline void _rcu_read_unlock(void) +{ + /* + * Finish using rcu before decrementing the pointer. + */ + smp_mb(); + _STORE_SHARED(urcu_reader->ctr, urcu_reader->ctr - RCU_GP_COUNT); +} + +#endif /* _URCU_BP_STATIC_H */