--- /dev/null
+/*
+ * workqueue.c
+ *
+ * Userspace RCU library - Userspace workqeues
+ *
+ * Copyright (c) 2010 Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+ * Copyright (c) 2017 Mathieu Desnoyers <mathieu.desnoyers@efficios.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"
+
+#include "workqueue.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 workqueue. */
+
+struct urcu_workqueue {
+ /*
+ * 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 loop_count;
+ void *priv;
+ void (*grace_period_fct)(struct urcu_workqueue *workqueue, void *priv);
+ void (*initialize_worker_fct)(struct urcu_workqueue *workqueue, void *priv);
+ void (*finalize_worker_fct)(struct urcu_workqueue *workqueue, void *priv);
+ void (*worker_before_pause_fct)(struct urcu_workqueue *workqueue, void *priv);
+ void (*worker_after_resume_fct)(struct urcu_workqueue *workqueue, void *priv);
+ void (*worker_before_wait_fct)(struct urcu_workqueue *workqueue, void *priv);
+ void (*worker_after_wake_up_fct)(struct urcu_workqueue *workqueue, void *priv);
+} __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
+
+struct urcu_workqueue_completion {
+ int barrier_count;
+ int32_t futex;
+ struct urcu_ref ref;
+};
+
+struct urcu_workqueue_completion_work {
+ struct urcu_work work;
+ struct urcu_workqueue_completion *completion;
+};
+
+/*
+ * 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 urcu_workqueue *workqueue)
+{
+ cpu_set_t mask;
+ int ret;
+
+ if (workqueue->cpu_affinity < 0)
+ return 0;
+ if (++workqueue->loop_count & SET_AFFINITY_CHECK_PERIOD_MASK)
+ return 0;
+ if (urcu_sched_getcpu() == workqueue->cpu_affinity)
+ return 0;
+
+ CPU_ZERO(&mask);
+ CPU_SET(workqueue->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 urcu_workqueue *workqueue)
+{
+ return 0;
+}
+#endif
+
+static void futex_wait(int32_t *futex)
+{
+ /* Read condition before read futex */
+ cmm_smp_mb();
+ if (uatomic_read(futex) != -1)
+ return;
+ while (futex_async(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 futex_wake_up(int32_t *futex)
+{
+ /* Write to condition before reading/writing futex */
+ cmm_smp_mb();
+ if (caa_unlikely(uatomic_read(futex) == -1)) {
+ uatomic_set(futex, 0);
+ if (futex_async(futex, FUTEX_WAKE, 1,
+ NULL, NULL, 0) < 0)
+ urcu_die(errno);
+ }
+}
+
+/* This is the code run by each worker thread. */
+
+static void *workqueue_thread(void *arg)
+{
+ unsigned long cbcount;
+ struct urcu_workqueue *workqueue = (struct urcu_workqueue *) arg;
+ int rt = !!(uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_RT);
+
+ if (set_thread_cpu_affinity(workqueue))
+ urcu_die(errno);
+
+ if (workqueue->initialize_worker_fct)
+ workqueue->initialize_worker_fct(workqueue, workqueue->priv);
+
+ if (!rt) {
+ uatomic_dec(&workqueue->futex);
+ /* Decrement futex before reading workqueue */
+ 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(workqueue))
+ urcu_die(errno);
+
+ if (uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_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.
+ */
+ if (workqueue->worker_before_pause_fct)
+ workqueue->worker_before_pause_fct(workqueue, workqueue->priv);
+ cmm_smp_mb__before_uatomic_or();
+ uatomic_or(&workqueue->flags, URCU_WORKQUEUE_PAUSED);
+ while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSE) != 0)
+ (void) poll(NULL, 0, 1);
+ uatomic_and(&workqueue->flags, ~URCU_WORKQUEUE_PAUSED);
+ cmm_smp_mb__after_uatomic_and();
+ if (workqueue->worker_after_resume_fct)
+ workqueue->worker_after_resume_fct(workqueue, workqueue->priv);
+ }
+
+ cds_wfcq_init(&cbs_tmp_head, &cbs_tmp_tail);
+ splice_ret = __cds_wfcq_splice_blocking(&cbs_tmp_head,
+ &cbs_tmp_tail, &workqueue->cbs_head, &workqueue->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) {
+ if (workqueue->grace_period_fct)
+ workqueue->grace_period_fct(workqueue, workqueue->priv);
+ 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(&workqueue->qlen, cbcount);
+ }
+ if (uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_STOP)
+ break;
+ if (workqueue->worker_before_wait_fct)
+ workqueue->worker_before_wait_fct(workqueue, workqueue->priv);
+ if (!rt) {
+ if (cds_wfcq_empty(&workqueue->cbs_head,
+ &workqueue->cbs_tail)) {
+ futex_wait(&workqueue->futex);
+ (void) poll(NULL, 0, 10);
+ uatomic_dec(&workqueue->futex);
+ /*
+ * Decrement futex before reading
+ * call_rcu list.
+ */
+ cmm_smp_mb();
+ } else {
+ (void) poll(NULL, 0, 10);
+ }
+ } else {
+ (void) poll(NULL, 0, 10);
+ }
+ if (workqueue->worker_after_wake_up_fct)
+ workqueue->worker_after_wake_up_fct(workqueue, workqueue->priv);
+ }
+ if (!rt) {
+ /*
+ * Read call_rcu list before write futex.
+ */
+ cmm_smp_mb();
+ uatomic_set(&workqueue->futex, 0);
+ }
+ if (workqueue->finalize_worker_fct)
+ workqueue->finalize_worker_fct(workqueue, workqueue->priv);
+ return NULL;
+}
+
+struct urcu_workqueue *urcu_workqueue_create(unsigned long flags,
+ int cpu_affinity, void *priv,
+ void (*grace_period_fct)(struct urcu_workqueue *workqueue, void *priv),
+ void (*initialize_worker_fct)(struct urcu_workqueue *workqueue, void *priv),
+ void (*finalize_worker_fct)(struct urcu_workqueue *workqueue, void *priv),
+ void (*worker_before_wait_fct)(struct urcu_workqueue *workqueue, void *priv),
+ void (*worker_after_wake_up_fct)(struct urcu_workqueue *workqueue, void *priv),
+ void (*worker_before_pause_fct)(struct urcu_workqueue *workqueue, void *priv),
+ void (*worker_after_resume_fct)(struct urcu_workqueue *workqueue, void *priv))
+{
+ struct urcu_workqueue *workqueue;
+ int ret;
+
+ workqueue = malloc(sizeof(*workqueue));
+ if (workqueue == NULL)
+ urcu_die(errno);
+ memset(workqueue, '\0', sizeof(*workqueue));
+ cds_wfcq_init(&workqueue->cbs_head, &workqueue->cbs_tail);
+ workqueue->qlen = 0;
+ workqueue->futex = 0;
+ workqueue->flags = flags;
+ workqueue->priv = priv;
+ workqueue->grace_period_fct = grace_period_fct;
+ workqueue->initialize_worker_fct = initialize_worker_fct;
+ workqueue->finalize_worker_fct = finalize_worker_fct;
+ workqueue->worker_before_wait_fct = worker_before_wait_fct;
+ workqueue->worker_after_wake_up_fct = worker_after_wake_up_fct;
+ workqueue->worker_before_pause_fct = worker_before_pause_fct;
+ workqueue->worker_after_resume_fct = worker_after_resume_fct;
+ workqueue->cpu_affinity = cpu_affinity;
+ workqueue->loop_count = 0;
+ cmm_smp_mb(); /* Structure initialized before pointer is planted. */
+ ret = pthread_create(&workqueue->tid, NULL, workqueue_thread, workqueue);
+ if (ret) {
+ urcu_die(ret);
+ }
+ return workqueue;
+}
+
+static void wake_worker_thread(struct urcu_workqueue *workqueue)
+{
+ if (!(_CMM_LOAD_SHARED(workqueue->flags) & URCU_CALL_RCU_RT))
+ futex_wake_up(&workqueue->futex);
+}
+
+static int urcu_workqueue_destroy_worker(struct urcu_workqueue *workqueue)
+{
+ int ret;
+ void *retval;
+
+ uatomic_or(&workqueue->flags, URCU_WORKQUEUE_STOP);
+ wake_worker_thread(workqueue);
+
+ ret = pthread_join(workqueue->tid, &retval);
+ if (ret) {
+ urcu_die(ret);
+ }
+ if (retval != NULL) {
+ urcu_die(EINVAL);
+ }
+ workqueue->flags &= ~URCU_WORKQUEUE_STOP;
+ workqueue->tid = 0;
+ return 0;
+}
+
+void urcu_workqueue_destroy(struct urcu_workqueue *workqueue)
+{
+ if (workqueue == NULL) {
+ return;
+ }
+ if (urcu_workqueue_destroy_worker(workqueue)) {
+ urcu_die(errno);
+ }
+ assert(cds_wfcq_empty(&workqueue->cbs_head, &workqueue->cbs_tail));
+ free(workqueue);
+}
+
+void urcu_workqueue_queue_work(struct urcu_workqueue *workqueue,
+ struct urcu_work *work,
+ void (*func)(struct urcu_work *work))
+{
+ cds_wfcq_node_init(&work->next);
+ work->func = func;
+ cds_wfcq_enqueue(&workqueue->cbs_head, &workqueue->cbs_tail, &work->next);
+ uatomic_inc(&workqueue->qlen);
+ wake_worker_thread(workqueue);
+}
+
+static
+void free_completion(struct urcu_ref *ref)
+{
+ struct urcu_workqueue_completion *completion;
+
+ completion = caa_container_of(ref, struct urcu_workqueue_completion, ref);
+ free(completion);
+}
+
+static
+void _urcu_workqueue_wait_complete(struct urcu_work *work)
+{
+ struct urcu_workqueue_completion_work *completion_work;
+ struct urcu_workqueue_completion *completion;
+
+ completion_work = caa_container_of(work, struct urcu_workqueue_completion_work, work);
+ completion = completion_work->completion;
+ if (!uatomic_sub_return(&completion->barrier_count, 1))
+ futex_wake_up(&completion->futex);
+ urcu_ref_put(&completion->ref, free_completion);
+ free(completion_work);
+}
+
+struct urcu_workqueue_completion *urcu_workqueue_create_completion(void)
+{
+ struct urcu_workqueue_completion *completion;
+
+ completion = calloc(sizeof(*completion), 1);
+ if (!completion)
+ urcu_die(errno);
+ urcu_ref_set(&completion->ref, 1);
+ completion->barrier_count = 0;
+ return completion;
+}
+
+void urcu_workqueue_destroy_completion(struct urcu_workqueue_completion *completion)
+{
+ urcu_ref_put(&completion->ref, free_completion);
+}
+
+void urcu_workqueue_wait_completion(struct urcu_workqueue_completion *completion)
+{
+ /* Wait for them */
+ for (;;) {
+ uatomic_dec(&completion->futex);
+ /* Decrement futex before reading barrier_count */
+ cmm_smp_mb();
+ if (!uatomic_read(&completion->barrier_count))
+ break;
+ futex_wait(&completion->futex);
+ }
+}
+
+void urcu_workqueue_queue_completion(struct urcu_workqueue *workqueue,
+ struct urcu_workqueue_completion *completion)
+{
+ struct urcu_workqueue_completion_work *work;
+
+ work = calloc(sizeof(*work), 1);
+ if (!work)
+ urcu_die(errno);
+ work->completion = completion;
+ urcu_ref_get(&completion->ref);
+ uatomic_inc(&completion->barrier_count);
+ urcu_workqueue_queue_work(workqueue, &work->work, _urcu_workqueue_wait_complete);
+}
+
+/*
+ * Wait for all in-flight work to complete execution.
+ */
+void urcu_workqueue_flush_queued_work(struct urcu_workqueue *workqueue)
+{
+ struct urcu_workqueue_completion *completion;
+
+ completion = urcu_workqueue_create_completion();
+ if (!completion)
+ urcu_die(ENOMEM);
+ urcu_workqueue_queue_completion(workqueue, completion);
+ urcu_workqueue_wait_completion(completion);
+ urcu_workqueue_destroy_completion(completion);
+}
+
+/* To be used in before fork handler. */
+void urcu_workqueue_pause_worker(struct urcu_workqueue *workqueue)
+{
+ uatomic_or(&workqueue->flags, URCU_WORKQUEUE_PAUSE);
+ cmm_smp_mb__after_uatomic_or();
+ wake_worker_thread(workqueue);
+
+ while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSED) == 0)
+ (void) poll(NULL, 0, 1);
+}
+
+/* To be used in after fork parent handler. */
+void urcu_workqueue_resume_worker(struct urcu_workqueue *workqueue)
+{
+ uatomic_and(&workqueue->flags, ~URCU_WORKQUEUE_PAUSE);
+ while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSED) != 0)
+ (void) poll(NULL, 0, 1);
+}
+
+void urcu_workqueue_create_worker(struct urcu_workqueue *workqueue)
+{
+ int ret;
+
+ /* Clear workqueue state from parent. */
+ workqueue->flags &= ~URCU_WORKQUEUE_PAUSED;
+ workqueue->flags &= ~URCU_WORKQUEUE_PAUSE;
+ workqueue->tid = 0;
+ ret = pthread_create(&workqueue->tid, NULL, workqueue_thread, workqueue);
+ if (ret) {
+ urcu_die(ret);
+ }
+}
--- /dev/null
+#ifndef _URCU_WORKQUEUE_H
+#define _URCU_WORKQUEUE_H
+
+/*
+ * workqueue.h
+ *
+ * Userspace RCU header - Userspace workqueues
+ *
+ * Copyright (c) 2009,2017 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
+ */
+
+#include <stdlib.h>
+#include <pthread.h>
+
+#include <urcu/wfcqueue.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Note that struct urcu_workqueue is opaque to callers. */
+
+struct urcu_workqueue;
+struct urcu_workqueue_completion;
+
+/* Flag values. */
+
+#define URCU_WORKQUEUE_RT (1U << 0)
+#define URCU_WORKQUEUE_STOP (1U << 1)
+#define URCU_WORKQUEUE_PAUSE (1U << 2)
+#define URCU_WORKQUEUE_PAUSED (1U << 3)
+
+/*
+ * The urcu_work data structure is placed in the structure to be acted
+ * upon via urcu_workqueue_queue_work().
+ */
+
+struct urcu_work {
+ struct cds_wfcq_node next;
+ void (*func)(struct urcu_work *head);
+};
+
+/*
+ * Exported functions
+ */
+
+struct urcu_workqueue *urcu_workqueue_create(unsigned long flags,
+ int cpu_affinity, void *priv,
+ void (*grace_period_fct)(struct urcu_workqueue *workqueue, void *priv),
+ void (*initialize_worker_fct)(struct urcu_workqueue *workqueue, void *priv),
+ void (*finalize_worker_fct)(struct urcu_workqueue *workqueue, void *priv),
+ void (*worker_before_wait_fct)(struct urcu_workqueue *workqueue, void *priv),
+ void (*worker_after_wake_up_fct)(struct urcu_workqueue *workqueue, void *priv),
+ void (*worker_before_pause_fct)(struct urcu_workqueue *workqueue, void *priv),
+ void (*worker_after_resume_fct)(struct urcu_workqueue *workqueue, void *priv));
+void urcu_workqueue_destroy(struct urcu_workqueue *workqueue);
+
+/*
+ * Never fails. Should not be used to enqueue work from worker threads
+ * after the application invokes urcu_workqueue_free.
+ */
+void urcu_workqueue_queue_work(struct urcu_workqueue *workqueue,
+ struct urcu_work *work,
+ void (*func)(struct urcu_work *work));
+
+struct urcu_workqueue_completion *urcu_workqueue_create_completion(void);
+void urcu_workqueue_destroy_completion(struct urcu_workqueue_completion *completion);
+
+void urcu_workqueue_queue_completion(struct urcu_workqueue *workqueue,
+ struct urcu_workqueue_completion *completion);
+void urcu_workqueue_wait_completion(struct urcu_workqueue_completion *completion);
+
+void urcu_workqueue_flush_queued_work(struct urcu_workqueue *workqueue);
+
+/*
+ * pause/resume/create worker threads. Can be used to pause worker
+ * threads across fork/clone while keeping the workqueue in place.
+ * Pause is used in parent pre-fork, resume in parent post-fork, create
+ * in child after-fork.
+ */
+void urcu_workqueue_pause_worker(struct urcu_workqueue *workqueue);
+void urcu_workqueue_resume_worker(struct urcu_workqueue *workqueue);
+void urcu_workqueue_create_worker(struct urcu_workqueue *workqueue);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _URCU_WORKQUEUE_H */
projects / urcu.git / commitdiff
