--- /dev/null
+/*
+ * urcu-call-rcu.c
+ *
+ * Userspace RCU library - batch memory reclamation with kernel API
+ *
+ * Copyright (c) 2010 Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+ *
+ * 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
+ */
+
+#include <stdio.h>
+#include <pthread.h>
+#include <signal.h>
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <poll.h>
+#include <sys/time.h>
+#include <syscall.h>
+#include <unistd.h>
+
+#include "config.h"
+#include "urcu/wfqueue.h"
+#include "urcu-call-rcu.h"
+#include "urcu-pointer.h"
+
+/* Data structure that identifies a call_rcu thread. */
+
+struct call_rcu_data {
+ struct cds_wfq_queue cbs;
+ unsigned long flags;
+ pthread_mutex_t mtx;
+ pthread_cond_t cond;
+ unsigned long qlen;
+ pthread_t tid;
+} __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
+
+/* Link a thread using call_rcu() to its call_rcu thread. */
+
+static __thread struct call_rcu_data *thread_call_rcu_data;
+
+/* Guard call_rcu thread creation. */
+
+static pthread_mutex_t call_rcu_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+/* If a given thread does not have its own call_rcu thread, this is default. */
+
+static struct call_rcu_data *default_call_rcu_data;
+
+extern void synchronize_rcu(void);
+
+/*
+ * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are
+ * available, then we can have call_rcu threads assigned to individual
+ * CPUs rather than only to specific threads.
+ */
+
+#if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF)
+
+/*
+ * Pointer to array of pointers to per-CPU call_rcu_data structures
+ * and # CPUs.
+ */
+
+static struct call_rcu_data **per_cpu_call_rcu_data;
+static long maxcpus;
+
+/* Allocate the array if it has not already been allocated. */
+
+static void alloc_cpu_call_rcu_data(void)
+{
+ struct call_rcu_data **p;
+ static int warned = 0;
+
+ if (maxcpus != 0)
+ return;
+ maxcpus = sysconf(_SC_NPROCESSORS_CONF);
+ if (maxcpus <= 0) {
+ return;
+ }
+ p = malloc(maxcpus * sizeof(*per_cpu_call_rcu_data));
+ if (p != NULL) {
+ memset(p, '\0', maxcpus * sizeof(*per_cpu_call_rcu_data));
+ per_cpu_call_rcu_data = p;
+ } else {
+ if (!warned) {
+ fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n");
+ }
+ warned = 1;
+ }
+}
+
+#else /* #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */
+
+static const struct call_rcu_data **per_cpu_call_rcu_data = NULL;
+static const long maxcpus = -1;
+
+static void alloc_cpu_call_rcu_data(void)
+{
+}
+
+static int sched_getcpu(void)
+{
+ return -1;
+}
+
+#endif /* #else #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */
+
+/* Acquire the specified pthread mutex. */
+
+static void call_rcu_lock(pthread_mutex_t *pmp)
+{
+ if (pthread_mutex_lock(pmp) != 0) {
+ perror("pthread_mutex_lock");
+ exit(-1);
+ }
+}
+
+/* Release the specified pthread mutex. */
+
+static void call_rcu_unlock(pthread_mutex_t *pmp)
+{
+ if (pthread_mutex_unlock(pmp) != 0) {
+ perror("pthread_mutex_unlock");
+ exit(-1);
+ }
+}
+
+/* This is the code run by each call_rcu thread. */
+
+static void *call_rcu_thread(void *arg)
+{
+ unsigned long cbcount;
+ struct cds_wfq_node *cbs;
+ struct cds_wfq_node **cbs_tail;
+ struct call_rcu_data *crdp = (struct call_rcu_data *)arg;
+ struct rcu_head *rhp;
+
+ thread_call_rcu_data = crdp;
+ for (;;) {
+ if (&crdp->cbs.head != _CMM_LOAD_SHARED(crdp->cbs.tail)) {
+ while ((cbs = _CMM_LOAD_SHARED(crdp->cbs.head)) == NULL)
+ poll(NULL, 0, 1);
+ _CMM_STORE_SHARED(crdp->cbs.head, NULL);
+ cbs_tail = (struct cds_wfq_node **)
+ uatomic_xchg(&crdp->cbs.tail, &crdp->cbs.head);
+ synchronize_rcu();
+ cbcount = 0;
+ do {
+ while (cbs->next == NULL &&
+ &cbs->next != cbs_tail)
+ poll(NULL, 0, 1);
+ if (cbs == &crdp->cbs.dummy) {
+ cbs = cbs->next;
+ continue;
+ }
+ rhp = (struct rcu_head *)cbs;
+ cbs = cbs->next;
+ rhp->func(rhp);
+ cbcount++;
+ } while (cbs != NULL);
+ uatomic_sub(&crdp->qlen, cbcount);
+ }
+ if (crdp->flags & URCU_CALL_RCU_RT)
+ poll(NULL, 0, 10);
+ else {
+ call_rcu_lock(&crdp->mtx);
+ _CMM_STORE_SHARED(crdp->flags,
+ crdp->flags & ~URCU_CALL_RCU_RUNNING);
+ if (&crdp->cbs.head ==
+ _CMM_LOAD_SHARED(crdp->cbs.tail) &&
+ pthread_cond_wait(&crdp->cond, &crdp->mtx) != 0) {
+ perror("pthread_cond_wait");
+ exit(-1);
+ }
+ _CMM_STORE_SHARED(crdp->flags,
+ crdp->flags | URCU_CALL_RCU_RUNNING);
+ poll(NULL, 0, 10);
+ call_rcu_unlock(&crdp->mtx);
+ }
+ }
+ return NULL; /* NOTREACHED */
+}
+
+/*
+ * Create both a call_rcu thread and the corresponding call_rcu_data
+ * structure, linking the structure in as specified.
+ */
+
+void call_rcu_data_init(struct call_rcu_data **crdpp, unsigned long flags)
+{
+ struct call_rcu_data *crdp;
+
+ crdp = malloc(sizeof(*crdp));
+ if (crdp == NULL) {
+ fprintf(stderr, "Out of memory.\n");
+ exit(-1);
+ }
+ memset(crdp, '\0', sizeof(*crdp));
+ cds_wfq_init(&crdp->cbs);
+ crdp->qlen = 0;
+ if (pthread_mutex_init(&crdp->mtx, NULL) != 0) {
+ perror("pthread_mutex_init");
+ exit(-1);
+ }
+ if (pthread_cond_init(&crdp->cond, NULL) != 0) {
+ perror("pthread_cond_init");
+ exit(-1);
+ }
+ crdp->flags = flags | URCU_CALL_RCU_RUNNING;
+ cmm_smp_mb(); /* Structure initialized before pointer is planted. */
+ *crdpp = crdp;
+ if (pthread_create(&crdp->tid, NULL, call_rcu_thread, crdp) != 0) {
+ perror("pthread_create");
+ exit(-1);
+ }
+}
+
+/*
+ * Return a pointer to the call_rcu_data structure for the specified
+ * CPU, returning NULL if there is none. We cannot automatically
+ * created it because the platform we are running on might not define
+ * sched_getcpu().
+ */
+
+struct call_rcu_data *get_cpu_call_rcu_data(int cpu)
+{
+ static int warned = 0;
+
+ if (per_cpu_call_rcu_data == NULL)
+ return NULL;
+ if (!warned && maxcpus > 0 && (cpu < 0 || maxcpus <= cpu)) {
+ fprintf(stderr, "[error] liburcu: get CPU # out of range\n");
+ warned = 1;
+ }
+ if (cpu < 0 || maxcpus <= cpu)
+ return NULL;
+ return per_cpu_call_rcu_data[cpu];
+}
+
+/*
+ * Return the tid corresponding to the call_rcu thread whose
+ * call_rcu_data structure is specified.
+ */
+
+pthread_t get_call_rcu_thread(struct call_rcu_data *crdp)
+{
+ return crdp->tid;
+}
+
+/*
+ * Create a call_rcu_data structure (with thread) and return a pointer.
+ */
+
+struct call_rcu_data *create_call_rcu_data(unsigned long flags)
+{
+ struct call_rcu_data *crdp;
+
+ call_rcu_data_init(&crdp, flags);
+ return crdp;
+}
+
+/*
+ * Set the specified CPU to use the specified call_rcu_data structure.
+ */
+
+int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp)
+{
+ int warned = 0;
+
+ call_rcu_lock(&call_rcu_mutex);
+ if (cpu < 0 || maxcpus <= cpu) {
+ if (!warned) {
+ fprintf(stderr, "[error] liburcu: set CPU # out of range\n");
+ warned = 1;
+ }
+ call_rcu_unlock(&call_rcu_mutex);
+ errno = EINVAL;
+ return -EINVAL;
+ }
+ alloc_cpu_call_rcu_data();
+ call_rcu_unlock(&call_rcu_mutex);
+ if (per_cpu_call_rcu_data == NULL) {
+ errno = ENOMEM;
+ return -ENOMEM;
+ }
+ per_cpu_call_rcu_data[cpu] = crdp;
+ return 0;
+}
+
+/*
+ * Return a pointer to the default call_rcu_data structure, creating
+ * one if need be. Because we never free call_rcu_data structures,
+ * we don't need to be in an RCU read-side critical section.
+ */
+
+struct call_rcu_data *get_default_call_rcu_data(void)
+{
+ if (default_call_rcu_data != NULL)
+ return rcu_dereference(default_call_rcu_data);
+ call_rcu_lock(&call_rcu_mutex);
+ if (default_call_rcu_data != NULL) {
+ call_rcu_unlock(&call_rcu_mutex);
+ return default_call_rcu_data;
+ }
+ call_rcu_data_init(&default_call_rcu_data, 0);
+ call_rcu_unlock(&call_rcu_mutex);
+ return default_call_rcu_data;
+}
+
+/*
+ * Return the call_rcu_data structure that applies to the currently
+ * running thread. Any call_rcu_data structure assigned specifically
+ * to this thread has first priority, followed by any call_rcu_data
+ * structure assigned to the CPU on which the thread is running,
+ * followed by the default call_rcu_data structure. If there is not
+ * yet a default call_rcu_data structure, one will be created.
+ */
+struct call_rcu_data *get_call_rcu_data(void)
+{
+ int curcpu;
+ static int warned = 0;
+
+ if (thread_call_rcu_data != NULL)
+ return thread_call_rcu_data;
+ if (maxcpus <= 0)
+ return get_default_call_rcu_data();
+ curcpu = sched_getcpu();
+ if (!warned && (curcpu < 0 || maxcpus <= curcpu)) {
+ fprintf(stderr, "[error] liburcu: gcrd CPU # out of range\n");
+ warned = 1;
+ }
+ if (curcpu >= 0 && maxcpus > curcpu &&
+ per_cpu_call_rcu_data != NULL &&
+ per_cpu_call_rcu_data[curcpu] != NULL)
+ return per_cpu_call_rcu_data[curcpu];
+ return get_default_call_rcu_data();
+}
+
+/*
+ * Return a pointer to this task's call_rcu_data if there is one.
+ */
+
+struct call_rcu_data *get_thread_call_rcu_data(void)
+{
+ return thread_call_rcu_data;
+}
+
+/*
+ * Set this task's call_rcu_data structure as specified, regardless
+ * of whether or not this task already had one. (This allows switching
+ * to and from real-time call_rcu threads, for example.)
+ */
+
+void set_thread_call_rcu_data(struct call_rcu_data *crdp)
+{
+ thread_call_rcu_data = crdp;
+}
+
+/*
+ * Create a separate call_rcu thread for each CPU. This does not
+ * replace a pre-existing call_rcu thread -- use the set_cpu_call_rcu_data()
+ * function if you want that behavior.
+ */
+
+int create_all_cpu_call_rcu_data(unsigned long flags)
+{
+ int i;
+ struct call_rcu_data *crdp;
+ int ret;
+
+ call_rcu_lock(&call_rcu_mutex);
+ alloc_cpu_call_rcu_data();
+ call_rcu_unlock(&call_rcu_mutex);
+ if (maxcpus <= 0) {
+ errno = EINVAL;
+ return -EINVAL;
+ }
+ if (per_cpu_call_rcu_data == NULL) {
+ errno = ENOMEM;
+ return -ENOMEM;
+ }
+ for (i = 0; i < maxcpus; i++) {
+ call_rcu_lock(&call_rcu_mutex);
+ if (get_cpu_call_rcu_data(i)) {
+ call_rcu_unlock(&call_rcu_mutex);
+ continue;
+ }
+ crdp = create_call_rcu_data(flags);
+ if (crdp == NULL) {
+ call_rcu_unlock(&call_rcu_mutex);
+ errno = ENOMEM;
+ return -ENOMEM;
+ }
+ call_rcu_unlock(&call_rcu_mutex);
+ if ((ret = set_cpu_call_rcu_data(i, crdp)) != 0) {
+ /* FIXME: Leaks crdp for now. */
+ return ret; /* Can happen on race. */
+ }
+ }
+ return 0;
+}
+
+/*
+ * Schedule a function to be invoked after a following grace period.
+ * This is the only function that must be called -- the others are
+ * only present to allow applications to tune their use of RCU for
+ * maximum performance.
+ *
+ * Note that unless a call_rcu thread has not already been created,
+ * the first invocation of call_rcu() will create one. So, if you
+ * need the first invocation of call_rcu() to be fast, make sure
+ * to create a call_rcu thread first. One way to accomplish this is
+ * "get_call_rcu_data();", and another is create_all_cpu_call_rcu_data().
+ */
+
+void call_rcu(struct rcu_head *head,
+ void (*func)(struct rcu_head *head))
+{
+ struct call_rcu_data *crdp;
+
+ cds_wfq_node_init(&head->next);
+ head->func = func;
+ crdp = get_call_rcu_data();
+ cds_wfq_enqueue(&crdp->cbs, &head->next);
+ uatomic_inc(&crdp->qlen);
+ if (!(_CMM_LOAD_SHARED(crdp->flags) & URCU_CALL_RCU_RT)) {
+ call_rcu_lock(&crdp->mtx);
+ if (!(_CMM_LOAD_SHARED(crdp->flags) & URCU_CALL_RCU_RUNNING)) {
+ if (pthread_cond_signal(&crdp->cond) != 0) {
+ perror("pthread_cond_signal");
+ exit(-1);
+ }
+ }
+ call_rcu_unlock(&crdp->mtx);
+ }
+}
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