+++ /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"
-#include "urcu/list.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;
- struct cds_list_head list;
-} __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
-
-/*
- * List of all call_rcu_data structures to keep valgrind happy.
- * Protected by call_rcu_mutex.
- */
-
-CDS_LIST_HEAD(call_rcu_data_list);
-
-/* 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_STOP)
- break;
- 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);
- }
- }
- call_rcu_lock(&crdp->mtx);
- crdp->flags |= URCU_CALL_RCU_STOPPED;
- call_rcu_unlock(&crdp->mtx);
- return NULL;
-}
-
-/*
- * Create both a call_rcu thread and the corresponding call_rcu_data
- * structure, linking the structure in as specified. Caller must hold
- * call_rcu_mutex.
- */
-
-static 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;
- cds_list_add(&crdp->list, &call_rcu_data_list);
- 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.
- */
-
-static struct call_rcu_data *__create_call_rcu_data(unsigned long flags)
-{
- struct call_rcu_data *crdp;
-
- call_rcu_data_init(&crdp, flags);
- return crdp;
-}
-
-struct call_rcu_data *create_call_rcu_data(unsigned long flags)
-{
- struct call_rcu_data *crdp;
-
- call_rcu_lock(&call_rcu_mutex);
- crdp = __create_call_rcu_data(flags);
- call_rcu_unlock(&call_rcu_mutex);
- return crdp;
-}
-
-/*
- * Set the specified CPU to use the specified call_rcu_data structure.
- *
- * Use NULL to remove a CPU's call_rcu_data structure, but it is
- * the caller's responsibility to dispose of the removed structure.
- * Use get_cpu_call_rcu_data() to obtain a pointer to the old structure
- * (prior to NULLing it out, of course).
- */
-
-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.)
- *
- * Use NULL to remove a thread's call_rcu_data structure, but it is
- * the caller's responsibility to dispose of the removed structure.
- * Use get_thread_call_rcu_data() to obtain a pointer to the old structure
- * (prior to NULLing it out, of course).
- */
-
-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;
-}
-
-/*
- * Wake up the call_rcu thread corresponding to the specified
- * call_rcu_data structure.
- */
-static void wake_call_rcu_thread(struct call_rcu_data *crdp)
-{
- 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);
- }
-}
-
-/*
- * 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);
- wake_call_rcu_thread(crdp);
-}
-
-/*
- * Free up the specified call_rcu_data structure, terminating the
- * associated call_rcu thread. The caller must have previously
- * removed the call_rcu_data structure from per-thread or per-CPU
- * usage. For example, set_cpu_call_rcu_data(cpu, NULL) for per-CPU
- * call_rcu_data structures or set_thread_call_rcu_data(NULL) for
- * per-thread call_rcu_data structures.
- *
- * We silently refuse to free up the default call_rcu_data structure
- * because that is where we put any leftover callbacks. Note that
- * the possibility of self-spawning callbacks makes it impossible
- * to execute all the callbacks in finite time without putting any
- * newly spawned callbacks somewhere else. The "somewhere else" of
- * last resort is the default call_rcu_data structure.
- *
- * We also silently refuse to free NULL pointers. This simplifies
- * the calling code.
- */
-void call_rcu_data_free(struct call_rcu_data *crdp)
-{
- struct cds_wfq_node *cbs;
- struct cds_wfq_node **cbs_tail;
- struct cds_wfq_node **cbs_endprev;
-
- if (crdp == NULL || crdp == default_call_rcu_data) {
- return;
- }
- if ((crdp->flags & URCU_CALL_RCU_STOPPED) == 0) {
- call_rcu_lock(&crdp->mtx);
- crdp->flags |= URCU_CALL_RCU_STOP;
- call_rcu_unlock(&crdp->mtx);
- wake_call_rcu_thread(crdp);
- while ((crdp->flags & URCU_CALL_RCU_STOPPED) == 0)
- poll(NULL, 0, 1);
- }
- 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);
- cbs_endprev = (struct cds_wfq_node **)
- uatomic_xchg(&default_call_rcu_data, cbs_tail);
- *cbs_endprev = cbs;
- uatomic_add(&default_call_rcu_data->qlen,
- uatomic_read(&crdp->qlen));
- cds_list_del(&crdp->list);
- free(crdp);
- }
-}
-
-/*
- * Clean up all the per-CPU call_rcu threads.
- */
-void free_all_cpu_call_rcu_data(void)
-{
- int cpu;
- struct call_rcu_data *crdp;
-
- if (maxcpus <= 0)
- return;
- for (cpu = 0; cpu < maxcpus; cpu++) {
- crdp = get_cpu_call_rcu_data(cpu);
- if (crdp == NULL)
- continue;
- set_cpu_call_rcu_data(cpu, NULL);
- call_rcu_data_free(crdp);
- }
-}
-
-/*
- * Acquire the call_rcu_mutex in order to ensure that the child sees
- * all of the call_rcu() data structures in a consistent state.
- * Suitable for pthread_atfork() and friends.
- */
-void call_rcu_before_fork(void)
-{
- call_rcu_lock(&call_rcu_mutex);
-}
-
-/*
- * Clean up call_rcu data structures in the parent of a successful fork()
- * that is not followed by exec() in the child. Suitable for
- * pthread_atfork() and friends.
- */
-void call_rcu_after_fork_parent(void)
-{
- call_rcu_unlock(&call_rcu_mutex);
-}
-
-/*
- * Clean up call_rcu data structures in the child of a successful fork()
- * that is not followed by exec(). Suitable for pthread_atfork() and
- * friends.
- */
-void call_rcu_after_fork_child(void)
-{
- struct call_rcu_data *crdp;
-
- /* Release the mutex. */
- call_rcu_unlock(&call_rcu_mutex);
-
- /*
- * Allocate a new default call_rcu_data structure in order
- * to get a working call_rcu thread to go with it.
- */
- default_call_rcu_data = NULL;
- (void)get_default_call_rcu_data();
-
- /* Dispose of all of the rest of the call_rcu_data structures. */
- while (call_rcu_data_list.next != call_rcu_data_list.prev) {
- crdp = cds_list_entry(call_rcu_data_list.prev,
- struct call_rcu_data, list);
- if (crdp == default_call_rcu_data)
- crdp = cds_list_entry(crdp->list.prev,
- struct call_rcu_data, list);
- crdp->flags = URCU_CALL_RCU_STOPPED;
- call_rcu_data_free(crdp);
- }
-}
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