X-Git-Url: http://git.efficios.com/?a=blobdiff_plain;f=include%2Flttng%2Furcu%2Fstatic%2Furcu-ust.h;fp=include%2Flttng%2Furcu%2Fstatic%2Furcu-ust.h;h=cbe27c09704c7bc43d36c4dcf4373834c0065426;hb=10544ee8af31afb239e3dfa71cb2fe09d3de3771;hp=0000000000000000000000000000000000000000;hpb=3336564f68cb964478db684e5e70815fc179e97b;p=deliverable%2Flttng-ust.git diff --git a/include/lttng/urcu/static/urcu-ust.h b/include/lttng/urcu/static/urcu-ust.h new file mode 100644 index 00000000..cbe27c09 --- /dev/null +++ b/include/lttng/urcu/static/urcu-ust.h @@ -0,0 +1,211 @@ +#ifndef _LTTNG_UST_URCU_STATIC_H +#define _LTTNG_UST_URCU_STATIC_H + +/* + * urcu-ust-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 +#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 lttng_ust_urcu_state { + LTTNG_UST_URCU_READER_ACTIVE_CURRENT, + LTTNG_UST_URCU_READER_ACTIVE_OLD, + LTTNG_UST_URCU_READER_INACTIVE, +}; + +/* + * The trick here is that LTTNG_UST_URCU_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 LTTNG_UST_URCU_GP_COUNT (1UL << 0) +/* Use the amount of bits equal to half of the architecture long size */ +#define LTTNG_UST_URCU_GP_CTR_PHASE (1UL << (sizeof(long) << 2)) +#define LTTNG_UST_URCU_GP_CTR_NEST_MASK (LTTNG_UST_URCU_GP_CTR_PHASE - 1) + +/* + * Used internally by _lttng_ust_urcu_read_lock. + */ +extern void lttng_ust_urcu_register(void); + +struct lttng_ust_urcu_gp { + /* + * Global grace period counter. + * Contains the current LTTNG_UST_URCU_GP_CTR_PHASE. + * Also has a LTTNG_UST_URCU_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 lttng_ust_urcu_gp lttng_ust_urcu_gp; + +struct lttng_ust_urcu_reader { + /* Data used by both reader and lttng_ust_urcu_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 lttng_ust_urcu_reader *, lttng_ust_urcu_reader); + +#ifdef CONFIG_RCU_FORCE_SYS_MEMBARRIER +#define lttng_ust_urcu_has_sys_membarrier 1 +#else +extern int lttng_ust_urcu_has_sys_membarrier; +#endif + +static inline void lttng_ust_urcu_smp_mb_slave(void) +{ + if (caa_likely(lttng_ust_urcu_has_sys_membarrier)) + cmm_barrier(); + else + cmm_smp_mb(); +} + +static inline enum lttng_ust_urcu_state lttng_ust_urcu_reader_state(unsigned long *ctr) +{ + unsigned long v; + + if (ctr == NULL) + return LTTNG_UST_URCU_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 & LTTNG_UST_URCU_GP_CTR_NEST_MASK)) + return LTTNG_UST_URCU_READER_INACTIVE; + if (!((v ^ lttng_ust_urcu_gp.ctr) & LTTNG_UST_URCU_GP_CTR_PHASE)) + return LTTNG_UST_URCU_READER_ACTIVE_CURRENT; + return LTTNG_UST_URCU_READER_ACTIVE_OLD; +} + +/* + * Helper for _lttng_ust_urcu_read_lock(). The format of lttng_ust_urcu_gp.ctr (as well as + * the per-thread rcu_reader.ctr) has the upper bits containing a count of + * _lttng_ust_urcu_read_lock() nesting, and a lower-order bit that contains either zero + * or LTTNG_UST_URCU_GP_CTR_PHASE. The smp_mb_slave() ensures that the accesses in + * _lttng_ust_urcu_read_lock() happen before the subsequent read-side critical section. + */ +static inline void _lttng_ust_urcu_read_lock_update(unsigned long tmp) +{ + if (caa_likely(!(tmp & LTTNG_UST_URCU_GP_CTR_NEST_MASK))) { + _CMM_STORE_SHARED(URCU_TLS(lttng_ust_urcu_reader)->ctr, _CMM_LOAD_SHARED(lttng_ust_urcu_gp.ctr)); + lttng_ust_urcu_smp_mb_slave(); + } else + _CMM_STORE_SHARED(URCU_TLS(lttng_ust_urcu_reader)->ctr, tmp + LTTNG_UST_URCU_GP_COUNT); +} + +/* + * Enter an RCU read-side critical section. + * + * The first cmm_barrier() call ensures that the compiler does not reorder + * the body of _lttng_ust_urcu_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 _lttng_ust_urcu_read_lock(void) +{ + unsigned long tmp; + + if (caa_unlikely(!URCU_TLS(lttng_ust_urcu_reader))) + lttng_ust_urcu_register(); /* If not yet registered. */ + cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */ + tmp = URCU_TLS(lttng_ust_urcu_reader)->ctr; + urcu_assert((tmp & LTTNG_UST_URCU_GP_CTR_NEST_MASK) != LTTNG_UST_URCU_GP_CTR_NEST_MASK); + _lttng_ust_urcu_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 _lttng_ust_urcu_read_unlock(void) +{ + unsigned long tmp; + + tmp = URCU_TLS(lttng_ust_urcu_reader)->ctr; + urcu_assert(tmp & LTTNG_UST_URCU_GP_CTR_NEST_MASK); + /* Finish using rcu before decrementing the pointer. */ + lttng_ust_urcu_smp_mb_slave(); + _CMM_STORE_SHARED(URCU_TLS(lttng_ust_urcu_reader)->ctr, tmp - LTTNG_UST_URCU_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 _lttng_ust_urcu_read_ongoing(void) +{ + if (caa_unlikely(!URCU_TLS(lttng_ust_urcu_reader))) + lttng_ust_urcu_register(); /* If not yet registered. */ + return URCU_TLS(lttng_ust_urcu_reader)->ctr & LTTNG_UST_URCU_GP_CTR_NEST_MASK; +} + +#ifdef __cplusplus +} +#endif + +#endif /* _LTTNG_UST_URCU_STATIC_H */