--- /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
+ */
+
+#define _LGPL_SOURCE
+#include <stdio.h>
+#include <pthread.h>
+#include <signal.h>
+#include <assert.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <errno.h>
+#include <poll.h>
+#include <sys/time.h>
+#include <unistd.h>
+#include <sched.h>
+
+#include "compat-getcpu.h"
+#include "urcu/wfcqueue.h"
+#include "urcu-call-rcu.h"
+#include "urcu-pointer.h"
+#include "urcu/list.h"
+#include "urcu/futex.h"
+#include "urcu/tls-compat.h"
+#include "urcu/ref.h"
+#include "urcu-die.h"
+
+#define SET_AFFINITY_CHECK_PERIOD (1U << 8) /* 256 */
+#define SET_AFFINITY_CHECK_PERIOD_MASK (SET_AFFINITY_CHECK_PERIOD - 1)
+
+/* Data structure that identifies a call_rcu thread. */
+
+struct call_rcu_data {
+ /*
+ * We do not align head on a different cache-line than tail
+ * mainly because call_rcu callback-invocation threads use
+ * batching ("splice") to get an entire list of callbacks, which
+ * effectively empties the queue, and requires to touch the tail
+ * anyway.
+ */
+ struct cds_wfcq_tail cbs_tail;
+ struct cds_wfcq_head cbs_head;
+ unsigned long flags;
+ int32_t futex;
+ unsigned long qlen; /* maintained for debugging. */
+ pthread_t tid;
+ int cpu_affinity;
+ unsigned long gp_count;
+ struct cds_list_head list;
+} __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
+
+struct call_rcu_completion {
+ int barrier_count;
+ int32_t futex;
+ struct urcu_ref ref;
+};
+
+struct call_rcu_completion_work {
+ struct rcu_head head;
+ struct call_rcu_completion *completion;
+};
+
+/*
+ * List of all call_rcu_data structures to keep valgrind happy.
+ * Protected by call_rcu_mutex.
+ */
+
+static CDS_LIST_HEAD(call_rcu_data_list);
+
+/* Link a thread using call_rcu() to its call_rcu thread. */
+
+static DEFINE_URCU_TLS(struct call_rcu_data *, thread_call_rcu_data);
+
+/*
+ * Guard call_rcu thread creation and atfork handlers.
+ */
+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;
+
+/*
+ * 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_SYSCONF) && (defined(HAVE_SCHED_GETCPU) || defined(HAVE_GETCPUID))
+
+/*
+ * Pointer to array of pointers to per-CPU call_rcu_data structures
+ * and # CPUs. per_cpu_call_rcu_data is a RCU-protected pointer to an
+ * array of RCU-protected pointers to call_rcu_data. call_rcu acts as a
+ * RCU read-side and reads per_cpu_call_rcu_data and the per-cpu pointer
+ * without mutex. The call_rcu_mutex protects updates.
+ */
+
+static struct call_rcu_data **per_cpu_call_rcu_data;
+static long maxcpus;
+
+static void maxcpus_reset(void)
+{
+ maxcpus = 0;
+}
+
+/* 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));
+ rcu_set_pointer(&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_SYSCONF) && defined(HAVE_SCHED_GETCPU) */
+
+/*
+ * per_cpu_call_rcu_data should be constant, but some functions below, used both
+ * for cases where cpu number is available and not available, assume it it not
+ * constant.
+ */
+static struct call_rcu_data **per_cpu_call_rcu_data = NULL;
+static const long maxcpus = -1;
+
+static void maxcpus_reset(void)
+{
+}
+
+static void alloc_cpu_call_rcu_data(void)
+{
+}
+
+#endif /* #else #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) */
+
+/* Acquire the specified pthread mutex. */
+
+static void call_rcu_lock(pthread_mutex_t *pmp)
+{
+ int ret;
+
+ ret = pthread_mutex_lock(pmp);
+ if (ret)
+ urcu_die(ret);
+}
+
+/* Release the specified pthread mutex. */
+
+static void call_rcu_unlock(pthread_mutex_t *pmp)
+{
+ int ret;
+
+ ret = pthread_mutex_unlock(pmp);
+ if (ret)
+ urcu_die(ret);
+}
+
+/*
+ * Periodically retry setting CPU affinity if we migrate.
+ * Losing affinity can be caused by CPU hotunplug/hotplug, or by
+ * cpuset(7).
+ */
+#if HAVE_SCHED_SETAFFINITY
+static
+int set_thread_cpu_affinity(struct call_rcu_data *crdp)
+{
+ cpu_set_t mask;
+ int ret;
+
+ if (crdp->cpu_affinity < 0)
+ return 0;
+ if (++crdp->gp_count & SET_AFFINITY_CHECK_PERIOD_MASK)
+ return 0;
+ if (urcu_sched_getcpu() == crdp->cpu_affinity)
+ return 0;
+
+ CPU_ZERO(&mask);
+ CPU_SET(crdp->cpu_affinity, &mask);
+#if SCHED_SETAFFINITY_ARGS == 2
+ ret = sched_setaffinity(0, &mask);
+#else
+ ret = sched_setaffinity(0, sizeof(mask), &mask);
+#endif
+ /*
+ * EINVAL is fine: can be caused by hotunplugged CPUs, or by
+ * cpuset(7). This is why we should always retry if we detect
+ * migration.
+ */
+ if (ret && errno == EINVAL) {
+ ret = 0;
+ errno = 0;
+ }
+ return ret;
+}
+#else
+static
+int set_thread_cpu_affinity(struct call_rcu_data *crdp)
+{
+ return 0;
+}
+#endif
+
+static void call_rcu_wait(struct call_rcu_data *crdp)
+{
+ /* Read call_rcu list before read futex */
+ cmm_smp_mb();
+ if (uatomic_read(&crdp->futex) != -1)
+ return;
+ while (futex_async(&crdp->futex, FUTEX_WAIT, -1,
+ NULL, NULL, 0)) {
+ switch (errno) {
+ case EWOULDBLOCK:
+ /* Value already changed. */
+ return;
+ case EINTR:
+ /* Retry if interrupted by signal. */
+ break; /* Get out of switch. */
+ default:
+ /* Unexpected error. */
+ urcu_die(errno);
+ }
+ }
+}
+
+static void call_rcu_wake_up(struct call_rcu_data *crdp)
+{
+ /* Write to call_rcu list before reading/writing futex */
+ cmm_smp_mb();
+ if (caa_unlikely(uatomic_read(&crdp->futex) == -1)) {
+ uatomic_set(&crdp->futex, 0);
+ if (futex_async(&crdp->futex, FUTEX_WAKE, 1,
+ NULL, NULL, 0) < 0)
+ urcu_die(errno);
+ }
+}
+
+static void call_rcu_completion_wait(struct call_rcu_completion *completion)
+{
+ /* Read completion barrier count before read futex */
+ cmm_smp_mb();
+ if (uatomic_read(&completion->futex) != -1)
+ return;
+ while (futex_async(&completion->futex, FUTEX_WAIT, -1,
+ NULL, NULL, 0)) {
+ switch (errno) {
+ case EWOULDBLOCK:
+ /* Value already changed. */
+ return;
+ case EINTR:
+ /* Retry if interrupted by signal. */
+ break; /* Get out of switch. */
+ default:
+ /* Unexpected error. */
+ urcu_die(errno);
+ }
+ }
+}
+
+static void call_rcu_completion_wake_up(struct call_rcu_completion *completion)
+{
+ /* Write to completion barrier count before reading/writing futex */
+ cmm_smp_mb();
+ if (caa_unlikely(uatomic_read(&completion->futex) == -1)) {
+ uatomic_set(&completion->futex, 0);
+ if (futex_async(&completion->futex, FUTEX_WAKE, 1,
+ NULL, NULL, 0) < 0)
+ urcu_die(errno);
+ }
+}
+
+/* This is the code run by each call_rcu thread. */
+
+static void *call_rcu_thread(void *arg)
+{
+ unsigned long cbcount;
+ struct call_rcu_data *crdp = (struct call_rcu_data *) arg;
+ int rt = !!(uatomic_read(&crdp->flags) & URCU_CALL_RCU_RT);
+
+ if (set_thread_cpu_affinity(crdp))
+ urcu_die(errno);
+
+ /*
+ * If callbacks take a read-side lock, we need to be registered.
+ */
+ rcu_register_thread();
+
+ URCU_TLS(thread_call_rcu_data) = crdp;
+ if (!rt) {
+ uatomic_dec(&crdp->futex);
+ /* Decrement futex before reading call_rcu list */
+ cmm_smp_mb();
+ }
+ for (;;) {
+ struct cds_wfcq_head cbs_tmp_head;
+ struct cds_wfcq_tail cbs_tmp_tail;
+ struct cds_wfcq_node *cbs, *cbs_tmp_n;
+ enum cds_wfcq_ret splice_ret;
+
+ if (set_thread_cpu_affinity(crdp))
+ urcu_die(errno);
+
+ if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) {
+ /*
+ * Pause requested. Become quiescent: remove
+ * ourself from all global lists, and don't
+ * process any callback. The callback lists may
+ * still be non-empty though.
+ */
+ rcu_unregister_thread();
+ cmm_smp_mb__before_uatomic_or();
+ uatomic_or(&crdp->flags, URCU_CALL_RCU_PAUSED);
+ while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) != 0)
+ (void) poll(NULL, 0, 1);
+ uatomic_and(&crdp->flags, ~URCU_CALL_RCU_PAUSED);
+ cmm_smp_mb__after_uatomic_and();
+ rcu_register_thread();
+ }
+
+ cds_wfcq_init(&cbs_tmp_head, &cbs_tmp_tail);
+ splice_ret = __cds_wfcq_splice_blocking(&cbs_tmp_head,
+ &cbs_tmp_tail, &crdp->cbs_head, &crdp->cbs_tail);
+ assert(splice_ret != CDS_WFCQ_RET_WOULDBLOCK);
+ assert(splice_ret != CDS_WFCQ_RET_DEST_NON_EMPTY);
+ if (splice_ret != CDS_WFCQ_RET_SRC_EMPTY) {
+ synchronize_rcu();
+ cbcount = 0;
+ __cds_wfcq_for_each_blocking_safe(&cbs_tmp_head,
+ &cbs_tmp_tail, cbs, cbs_tmp_n) {
+ struct rcu_head *rhp;
+
+ rhp = caa_container_of(cbs,
+ struct rcu_head, next);
+ rhp->func(rhp);
+ cbcount++;
+ }
+ uatomic_sub(&crdp->qlen, cbcount);
+ }
+ if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOP)
+ break;
+ rcu_thread_offline();
+ if (!rt) {
+ if (cds_wfcq_empty(&crdp->cbs_head,
+ &crdp->cbs_tail)) {
+ call_rcu_wait(crdp);
+ (void) poll(NULL, 0, 10);
+ uatomic_dec(&crdp->futex);
+ /*
+ * Decrement futex before reading
+ * call_rcu list.
+ */
+ cmm_smp_mb();
+ } else {
+ (void) poll(NULL, 0, 10);
+ }
+ } else {
+ (void) poll(NULL, 0, 10);
+ }
+ rcu_thread_online();
+ }
+ if (!rt) {
+ /*
+ * Read call_rcu list before write futex.
+ */
+ cmm_smp_mb();
+ uatomic_set(&crdp->futex, 0);
+ }
+ uatomic_or(&crdp->flags, URCU_CALL_RCU_STOPPED);
+ rcu_unregister_thread();
+ 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,
+ int cpu_affinity)
+{
+ struct call_rcu_data *crdp;
+ int ret;
+
+ crdp = malloc(sizeof(*crdp));
+ if (crdp == NULL)
+ urcu_die(errno);
+ memset(crdp, '\0', sizeof(*crdp));
+ cds_wfcq_init(&crdp->cbs_head, &crdp->cbs_tail);
+ crdp->qlen = 0;
+ crdp->futex = 0;
+ crdp->flags = flags;
+ cds_list_add(&crdp->list, &call_rcu_data_list);
+ crdp->cpu_affinity = cpu_affinity;
+ crdp->gp_count = 0;
+ cmm_smp_mb(); /* Structure initialized before pointer is planted. */
+ *crdpp = crdp;
+ ret = pthread_create(&crdp->tid, NULL, call_rcu_thread, crdp);
+ if (ret)
+ urcu_die(ret);
+}
+
+/*
+ * 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
+ * urcu_sched_getcpu().
+ *
+ * The call to this function and use of the returned call_rcu_data
+ * should be protected by RCU read-side lock.
+ */
+
+struct call_rcu_data *get_cpu_call_rcu_data(int cpu)
+{
+ static int warned = 0;
+ struct call_rcu_data **pcpu_crdp;
+
+ pcpu_crdp = rcu_dereference(per_cpu_call_rcu_data);
+ if (pcpu_crdp == 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 rcu_dereference(pcpu_crdp[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,
+ int cpu_affinity)
+{
+ struct call_rcu_data *crdp;
+
+ call_rcu_data_init(&crdp, flags, cpu_affinity);
+ return crdp;
+}
+
+struct call_rcu_data *create_call_rcu_data(unsigned long flags,
+ int cpu_affinity)
+{
+ struct call_rcu_data *crdp;
+
+ call_rcu_lock(&call_rcu_mutex);
+ crdp = __create_call_rcu_data(flags, cpu_affinity);
+ 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).
+ *
+ * The caller must wait for a grace-period to pass between return from
+ * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the
+ * previous call rcu data as argument.
+ */
+
+int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp)
+{
+ static int warned = 0;
+
+ call_rcu_lock(&call_rcu_mutex);
+ alloc_cpu_call_rcu_data();
+ 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;
+ }
+
+ if (per_cpu_call_rcu_data == NULL) {
+ call_rcu_unlock(&call_rcu_mutex);
+ errno = ENOMEM;
+ return -ENOMEM;
+ }
+
+ if (per_cpu_call_rcu_data[cpu] != NULL && crdp != NULL) {
+ call_rcu_unlock(&call_rcu_mutex);
+ errno = EEXIST;
+ return -EEXIST;
+ }
+
+ rcu_set_pointer(&per_cpu_call_rcu_data[cpu], crdp);
+ call_rcu_unlock(&call_rcu_mutex);
+ 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, -1);
+ 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.
+ *
+ * Calls to this function and use of the returned call_rcu_data should
+ * be protected by RCU read-side lock.
+ */
+struct call_rcu_data *get_call_rcu_data(void)
+{
+ struct call_rcu_data *crd;
+
+ if (URCU_TLS(thread_call_rcu_data) != NULL)
+ return URCU_TLS(thread_call_rcu_data);
+
+ if (maxcpus > 0) {
+ crd = get_cpu_call_rcu_data(urcu_sched_getcpu());
+ if (crd)
+ return crd;
+ }
+
+ 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 URCU_TLS(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)
+{
+ URCU_TLS(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. Should be paired with
+ * free_all_cpu_call_rcu_data() to teardown these call_rcu worker
+ * threads.
+ */
+
+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, i);
+ 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) {
+ call_rcu_data_free(crdp);
+
+ /* it has been created by other thread */
+ if (ret == -EEXIST)
+ continue;
+
+ return ret;
+ }
+ }
+ 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_wake_up(crdp);
+}
+
+static void _call_rcu(struct rcu_head *head,
+ void (*func)(struct rcu_head *head),
+ struct call_rcu_data *crdp)
+{
+ cds_wfcq_node_init(&head->next);
+ head->func = func;
+ cds_wfcq_enqueue(&crdp->cbs_head, &crdp->cbs_tail, &head->next);
+ uatomic_inc(&crdp->qlen);
+ wake_call_rcu_thread(crdp);
+}
+
+/*
+ * 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().
+ *
+ * call_rcu must be called by registered RCU read-side threads.
+ */
+void call_rcu(struct rcu_head *head,
+ void (*func)(struct rcu_head *head))
+{
+ struct call_rcu_data *crdp;
+
+ /* Holding rcu read-side lock across use of per-cpu crdp */
+ _rcu_read_lock();
+ crdp = get_call_rcu_data();
+ _call_rcu(head, func, crdp);
+ _rcu_read_unlock();
+}
+
+/*
+ * 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.
+ *
+ * The caller must wait for a grace-period to pass between return from
+ * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the
+ * previous call rcu data as argument.
+ *
+ * Note: introducing __cds_wfcq_splice_blocking() in this function fixed
+ * a list corruption bug in the 0.7.x series. The equivalent fix
+ * appeared in 0.6.8 for the stable-0.6 branch.
+ */
+void call_rcu_data_free(struct call_rcu_data *crdp)
+{
+ if (crdp == NULL || crdp == default_call_rcu_data) {
+ return;
+ }
+ if ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0) {
+ uatomic_or(&crdp->flags, URCU_CALL_RCU_STOP);
+ wake_call_rcu_thread(crdp);
+ while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0)
+ (void) poll(NULL, 0, 1);
+ }
+ if (!cds_wfcq_empty(&crdp->cbs_head, &crdp->cbs_tail)) {
+ /* Create default call rcu data if need be */
+ (void) get_default_call_rcu_data();
+ __cds_wfcq_splice_blocking(&default_call_rcu_data->cbs_head,
+ &default_call_rcu_data->cbs_tail,
+ &crdp->cbs_head, &crdp->cbs_tail);
+ uatomic_add(&default_call_rcu_data->qlen,
+ uatomic_read(&crdp->qlen));
+ wake_call_rcu_thread(default_call_rcu_data);
+ }
+
+ call_rcu_lock(&call_rcu_mutex);
+ cds_list_del(&crdp->list);
+ call_rcu_unlock(&call_rcu_mutex);
+
+ 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;
+ static int warned = 0;
+
+ if (maxcpus <= 0)
+ return;
+
+ crdp = malloc(sizeof(*crdp) * maxcpus);
+ if (!crdp) {
+ if (!warned) {
+ fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n");
+ }
+ warned = 1;
+ return;
+ }
+
+ for (cpu = 0; cpu < maxcpus; cpu++) {
+ crdp[cpu] = get_cpu_call_rcu_data(cpu);
+ if (crdp[cpu] == NULL)
+ continue;
+ set_cpu_call_rcu_data(cpu, NULL);
+ }
+ /*
+ * Wait for call_rcu sites acting as RCU readers of the
+ * call_rcu_data to become quiescent.
+ */
+ synchronize_rcu();
+ for (cpu = 0; cpu < maxcpus; cpu++) {
+ if (crdp[cpu] == NULL)
+ continue;
+ call_rcu_data_free(crdp[cpu]);
+ }
+ free(crdp);
+}
+
+static
+void free_completion(struct urcu_ref *ref)
+{
+ struct call_rcu_completion *completion;
+
+ completion = caa_container_of(ref, struct call_rcu_completion, ref);
+ free(completion);
+}
+
+static
+void _rcu_barrier_complete(struct rcu_head *head)
+{
+ struct call_rcu_completion_work *work;
+ struct call_rcu_completion *completion;
+
+ work = caa_container_of(head, struct call_rcu_completion_work, head);
+ completion = work->completion;
+ if (!uatomic_sub_return(&completion->barrier_count, 1))
+ call_rcu_completion_wake_up(completion);
+ urcu_ref_put(&completion->ref, free_completion);
+ free(work);
+}
+
+/*
+ * Wait for all in-flight call_rcu callbacks to complete execution.
+ */
+void rcu_barrier(void)
+{
+ struct call_rcu_data *crdp;
+ struct call_rcu_completion *completion;
+ int count = 0;
+ int was_online;
+
+ /* Put in offline state in QSBR. */
+ was_online = _rcu_read_ongoing();
+ if (was_online)
+ rcu_thread_offline();
+ /*
+ * Calling a rcu_barrier() within a RCU read-side critical
+ * section is an error.
+ */
+ if (_rcu_read_ongoing()) {
+ static int warned = 0;
+
+ if (!warned) {
+ fprintf(stderr, "[error] liburcu: rcu_barrier() called from within RCU read-side critical section.\n");
+ }
+ warned = 1;
+ goto online;
+ }
+
+ completion = calloc(sizeof(*completion), 1);
+ if (!completion)
+ urcu_die(errno);
+
+ call_rcu_lock(&call_rcu_mutex);
+ cds_list_for_each_entry(crdp, &call_rcu_data_list, list)
+ count++;
+
+ /* Referenced by rcu_barrier() and each call_rcu thread. */
+ urcu_ref_set(&completion->ref, count + 1);
+ completion->barrier_count = count;
+
+ cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
+ struct call_rcu_completion_work *work;
+
+ work = calloc(sizeof(*work), 1);
+ if (!work)
+ urcu_die(errno);
+ work->completion = completion;
+ _call_rcu(&work->head, _rcu_barrier_complete, crdp);
+ }
+ call_rcu_unlock(&call_rcu_mutex);
+
+ /* Wait for them */
+ for (;;) {
+ uatomic_dec(&completion->futex);
+ /* Decrement futex before reading barrier_count */
+ cmm_smp_mb();
+ if (!uatomic_read(&completion->barrier_count))
+ break;
+ call_rcu_completion_wait(completion);
+ }
+
+ urcu_ref_put(&completion->ref, free_completion);
+
+online:
+ if (was_online)
+ rcu_thread_online();
+}
+
+/*
+ * Acquire the call_rcu_mutex in order to ensure that the child sees
+ * all of the call_rcu() data structures in a consistent state. Ensure
+ * that all call_rcu threads are in a quiescent state across fork.
+ * Suitable for pthread_atfork() and friends.
+ */
+void call_rcu_before_fork(void)
+{
+ struct call_rcu_data *crdp;
+
+ call_rcu_lock(&call_rcu_mutex);
+
+ cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
+ uatomic_or(&crdp->flags, URCU_CALL_RCU_PAUSE);
+ cmm_smp_mb__after_uatomic_or();
+ wake_call_rcu_thread(crdp);
+ }
+ cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
+ while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSED) == 0)
+ (void) poll(NULL, 0, 1);
+ }
+}
+
+/*
+ * 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)
+{
+ struct call_rcu_data *crdp;
+
+ cds_list_for_each_entry(crdp, &call_rcu_data_list, list)
+ uatomic_and(&crdp->flags, ~URCU_CALL_RCU_PAUSE);
+ cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
+ while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSED) != 0)
+ (void) poll(NULL, 0, 1);
+ }
+ 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, *next;
+
+ /* Release the mutex. */
+ call_rcu_unlock(&call_rcu_mutex);
+
+ /* Do nothing when call_rcu() has not been used */
+ if (cds_list_empty(&call_rcu_data_list))
+ return;
+
+ /*
+ * 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();
+
+ /* Cleanup call_rcu_data pointers before use */
+ maxcpus_reset();
+ free(per_cpu_call_rcu_data);
+ rcu_set_pointer(&per_cpu_call_rcu_data, NULL);
+ URCU_TLS(thread_call_rcu_data) = NULL;
+
+ /*
+ * Dispose of all of the rest of the call_rcu_data structures.
+ * Leftover call_rcu callbacks will be merged into the new
+ * default call_rcu thread queue.
+ */
+ cds_list_for_each_entry_safe(crdp, next, &call_rcu_data_list, list) {
+ if (crdp == default_call_rcu_data)
+ continue;
+ uatomic_set(&crdp->flags, URCU_CALL_RCU_STOPPED);
+ call_rcu_data_free(crdp);
+ }
+}
projects / urcu.git / blobdiff