--- /dev/null
+#ifndef _URCU_STATIC_H
+#define _URCU_STATIC_H
+
+/*
+ * urcu-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 <mathieu.desnoyers@efficios.com>
+ * 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 <stdlib.h>
+#include <pthread.h>
+#include <unistd.h>
+#include <stdint.h>
+
+#include <urcu/compiler.h>
+#include <urcu/arch.h>
+#include <urcu/system.h>
+#include <urcu/uatomic.h>
+#include <urcu/list.h>
+#include <urcu/futex.h>
+#include <urcu/tls-compat.h>
+#include <urcu/rand-compat.h>
+#include <urcu/debug.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Default is RCU_MEMBARRIER */
+#if !defined(RCU_MEMBARRIER) && !defined(RCU_MB) && !defined(RCU_SIGNAL)
+#define RCU_MEMBARRIER
+#endif
+
+/*
+ * 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.
+ */
+
+/*
+ * The signal number used by the RCU library can be overridden with
+ * -DSIGRCU= when compiling the library.
+ * Provide backward compatibility for liburcu 0.3.x SIGURCU.
+ */
+#ifdef SIGURCU
+#define SIGRCU SIGURCU
+#endif
+
+#ifndef SIGRCU
+#define SIGRCU SIGUSR1
+#endif
+
+enum rcu_state {
+ RCU_READER_ACTIVE_CURRENT,
+ RCU_READER_ACTIVE_OLD,
+ RCU_READER_INACTIVE,
+};
+
+/*
+ * Slave barriers are only guaranteed to be ordered wrt master barriers.
+ *
+ * The pair ordering is detailed as (O: ordered, X: not ordered) :
+ * slave master
+ * slave X O
+ * master O O
+ */
+
+#ifdef RCU_MEMBARRIER
+extern int rcu_has_sys_membarrier;
+
+static inline void smp_mb_slave(void)
+{
+ if (caa_likely(rcu_has_sys_membarrier))
+ cmm_barrier();
+ else
+ cmm_smp_mb();
+}
+#endif
+
+#ifdef RCU_MB
+static inline void smp_mb_slave(void)
+{
+ cmm_smp_mb();
+}
+#endif
+
+#ifdef RCU_SIGNAL
+static inline void smp_mb_slave(void)
+{
+ cmm_barrier();
+}
+#endif
+
+/*
+ * 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(unsigned long) << 2))
+#define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_PHASE - 1)
+
+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;
+
+ int32_t futex;
+} __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;
+ char need_mb;
+ /* Data used for registry */
+ struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
+ pthread_t tid;
+ /* Reader registered flag, for internal checks. */
+ unsigned int registered:1;
+};
+
+extern DECLARE_URCU_TLS(struct rcu_reader, rcu_reader);
+
+/*
+ * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
+ */
+static inline void wake_up_gp(void)
+{
+ if (caa_unlikely(uatomic_read(&rcu_gp.futex) == -1)) {
+ uatomic_set(&rcu_gp.futex, 0);
+ /*
+ * Ignoring return value until we can make this function
+ * return something (because urcu_die() is not publicly
+ * exposed).
+ */
+ (void) futex_async(&rcu_gp.futex, FUTEX_WAKE, 1,
+ NULL, NULL, 0);
+ }
+}
+
+static inline enum rcu_state rcu_reader_state(unsigned long *ctr)
+{
+ unsigned long v;
+
+ /*
+ * 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));
+ 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;
+
+ urcu_assert(URCU_TLS(rcu_reader).registered);
+ cmm_barrier();
+ tmp = URCU_TLS(rcu_reader).ctr;
+ urcu_assert((tmp & RCU_GP_CTR_NEST_MASK) != RCU_GP_CTR_NEST_MASK);
+ _rcu_read_lock_update(tmp);
+}
+
+/*
+ * This is a helper function for _rcu_read_unlock().
+ *
+ * The first smp_mb_slave() call ensures that the critical section is
+ * seen to precede the store to rcu_reader.ctr.
+ * The second smp_mb_slave() call ensures that we write to rcu_reader.ctr
+ * before reading the update-side futex.
+ */
+static inline void _rcu_read_unlock_update_and_wakeup(unsigned long tmp)
+{
+ if (caa_likely((tmp & RCU_GP_CTR_NEST_MASK) == RCU_GP_COUNT)) {
+ smp_mb_slave();
+ _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, tmp - RCU_GP_COUNT);
+ smp_mb_slave();
+ wake_up_gp();
+ } else
+ _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, tmp - RCU_GP_COUNT);
+}
+
+/*
+ * Exit an RCU read-side crtical section. Both this function and its
+ * helper are smaller than 10 lines of code, and are intended to be
+ * usable by non-LGPL code, as called out in LGPL.
+ */
+static inline void _rcu_read_unlock(void)
+{
+ unsigned long tmp;
+
+ urcu_assert(URCU_TLS(rcu_reader).registered);
+ tmp = URCU_TLS(rcu_reader).ctr;
+ urcu_assert(tmp & RCU_GP_CTR_NEST_MASK);
+ _rcu_read_unlock_update_and_wakeup(tmp);
+ 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)
+{
+ return URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK;
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _URCU_STATIC_H */
projects / userspace-rcu.git / blobdiff