--- /dev/null
+#ifndef _URCU_QSBR_STATIC_H
+#define _URCU_QSBR_STATIC_H
+
+/*
+ * urcu-qsbr-static.h
+ *
+ * Userspace RCU QSBR 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 <limits.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/debug.h>
+
+#ifdef __cplusplus
+extern "C" {
+#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.
+ */
+
+enum rcu_state {
+ RCU_READER_ACTIVE_CURRENT,
+ RCU_READER_ACTIVE_OLD,
+ RCU_READER_INACTIVE,
+};
+
+#define RCU_GP_ONLINE (1UL << 0)
+#define RCU_GP_CTR (1UL << 1)
+
+struct rcu_gp {
+ /*
+ * 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.
+ */
+ 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;
+ /* Data used for registry */
+ struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
+ int waiting;
+ 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(_CMM_LOAD_SHARED(URCU_TLS(rcu_reader).waiting))) {
+ _CMM_STORE_SHARED(URCU_TLS(rcu_reader).waiting, 0);
+ cmm_smp_mb();
+ if (uatomic_read(&rcu_gp.futex) != -1)
+ return;
+ 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_noasync(&rcu_gp.futex, FUTEX_WAKE, 1,
+ NULL, NULL, 0);
+ }
+}
+
+static inline enum rcu_state rcu_reader_state(unsigned long *ctr)
+{
+ unsigned long v;
+
+ v = CMM_LOAD_SHARED(*ctr);
+ if (!v)
+ return RCU_READER_INACTIVE;
+ if (v == rcu_gp.ctr)
+ return RCU_READER_ACTIVE_CURRENT;
+ return RCU_READER_ACTIVE_OLD;
+}
+
+/*
+ * Enter an 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 void _rcu_read_lock(void)
+{
+ urcu_assert(URCU_TLS(rcu_reader).ctr);
+}
+
+/*
+ * Exit an 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 void _rcu_read_unlock(void)
+{
+ urcu_assert(URCU_TLS(rcu_reader).ctr);
+}
+
+/*
+ * 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;
+}
+
+/*
+ * This is a helper function for _rcu_quiescent_state().
+ * The first cmm_smp_mb() ensures memory accesses in the prior read-side
+ * critical sections are not reordered with store to
+ * URCU_TLS(rcu_reader).ctr, and ensures that mutexes held within an
+ * offline section that would happen to end with this
+ * rcu_quiescent_state() call are not reordered with
+ * store to URCU_TLS(rcu_reader).ctr.
+ */
+static inline void _rcu_quiescent_state_update_and_wakeup(unsigned long gp_ctr)
+{
+ cmm_smp_mb();
+ _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, gp_ctr);
+ cmm_smp_mb(); /* write URCU_TLS(rcu_reader).ctr before read futex */
+ wake_up_gp();
+ cmm_smp_mb();
+}
+
+/*
+ * Inform RCU of a quiescent state.
+ *
+ * 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.
+ *
+ * We skip the memory barriers and gp store if our local ctr already
+ * matches the global rcu_gp.ctr value: this is OK because a prior
+ * _rcu_quiescent_state() or _rcu_thread_online() already updated it
+ * within our thread, so we have no quiescent state to report.
+ */
+static inline void _rcu_quiescent_state(void)
+{
+ unsigned long gp_ctr;
+
+ urcu_assert(URCU_TLS(rcu_reader).registered);
+ if ((gp_ctr = CMM_LOAD_SHARED(rcu_gp.ctr)) == URCU_TLS(rcu_reader).ctr)
+ return;
+ _rcu_quiescent_state_update_and_wakeup(gp_ctr);
+}
+
+/*
+ * Take a thread offline, prohibiting it from entering further RCU
+ * read-side critical sections.
+ *
+ * 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 void _rcu_thread_offline(void)
+{
+ urcu_assert(URCU_TLS(rcu_reader).registered);
+ cmm_smp_mb();
+ CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, 0);
+ cmm_smp_mb(); /* write URCU_TLS(rcu_reader).ctr before read futex */
+ wake_up_gp();
+ cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
+}
+
+/*
+ * Bring a thread online, allowing it to once again enter RCU
+ * read-side critical sections.
+ *
+ * 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 void _rcu_thread_online(void)
+{
+ urcu_assert(URCU_TLS(rcu_reader).registered);
+ cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
+ _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, CMM_LOAD_SHARED(rcu_gp.ctr));
+ cmm_smp_mb();
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _URCU_QSBR_STATIC_H */
projects / userspace-rcu.git / blobdiff