+++ /dev/null
-/*
- * urcu-defer.c
- *
- * Userspace RCU library - batch memory reclamation
- *
- * Copyright (c) 2009 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
- */
-
-#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 "urcu/urcu-futex.h"
-#include "urcu-defer-static.h"
-/* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
-#include "urcu-defer.h"
-
-void __attribute__((destructor)) rcu_defer_exit(void);
-
-extern void synchronize_rcu(void);
-
-/*
- * rcu_defer_mutex nests inside defer_thread_mutex.
- */
-static pthread_mutex_t rcu_defer_mutex = PTHREAD_MUTEX_INITIALIZER;
-static pthread_mutex_t defer_thread_mutex = PTHREAD_MUTEX_INITIALIZER;
-
-static int defer_thread_futex;
-
-/*
- * Written to only by each individual deferer. Read by both the deferer and
- * the reclamation tread.
- */
-static struct defer_queue __thread defer_queue;
-static CDS_LIST_HEAD(registry);
-static pthread_t tid_defer;
-
-static void mutex_lock(pthread_mutex_t *mutex)
-{
- int ret;
-
-#ifndef DISTRUST_SIGNALS_EXTREME
- ret = pthread_mutex_lock(mutex);
- if (ret) {
- perror("Error in pthread mutex lock");
- exit(-1);
- }
-#else /* #ifndef DISTRUST_SIGNALS_EXTREME */
- while ((ret = pthread_mutex_trylock(mutex)) != 0) {
- if (ret != EBUSY && ret != EINTR) {
- printf("ret = %d, errno = %d\n", ret, errno);
- perror("Error in pthread mutex lock");
- exit(-1);
- }
- pthread_testcancel();
- poll(NULL,0,10);
- }
-#endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
-}
-
-static void mutex_unlock(pthread_mutex_t *mutex)
-{
- int ret;
-
- ret = pthread_mutex_unlock(mutex);
- if (ret) {
- perror("Error in pthread mutex unlock");
- exit(-1);
- }
-}
-
-/*
- * Wake-up any waiting defer thread. Called from many concurrent threads.
- */
-static void wake_up_defer(void)
-{
- if (unlikely(uatomic_read(&defer_thread_futex) == -1)) {
- uatomic_set(&defer_thread_futex, 0);
- futex_noasync(&defer_thread_futex, FUTEX_WAKE, 1,
- NULL, NULL, 0);
- }
-}
-
-static unsigned long rcu_defer_num_callbacks(void)
-{
- unsigned long num_items = 0, head;
- struct defer_queue *index;
-
- mutex_lock(&rcu_defer_mutex);
- cds_list_for_each_entry(index, ®istry, list) {
- head = CMM_LOAD_SHARED(index->head);
- num_items += head - index->tail;
- }
- mutex_unlock(&rcu_defer_mutex);
- return num_items;
-}
-
-/*
- * Defer thread waiting. Single thread.
- */
-static void wait_defer(void)
-{
- uatomic_dec(&defer_thread_futex);
- cmm_smp_mb(); /* Write futex before read queue */
- if (rcu_defer_num_callbacks()) {
- cmm_smp_mb(); /* Read queue before write futex */
- /* Callbacks are queued, don't wait. */
- uatomic_set(&defer_thread_futex, 0);
- } else {
- cmm_smp_rmb(); /* Read queue before read futex */
- if (uatomic_read(&defer_thread_futex) == -1)
- futex_noasync(&defer_thread_futex, FUTEX_WAIT, -1,
- NULL, NULL, 0);
- }
-}
-
-/*
- * Must be called after Q.S. is reached.
- */
-static void rcu_defer_barrier_queue(struct defer_queue *queue,
- unsigned long head)
-{
- unsigned long i;
- void (*fct)(void *p);
- void *p;
-
- /*
- * Tail is only modified when lock is held.
- * Head is only modified by owner thread.
- */
-
- for (i = queue->tail; i != head;) {
- cmm_smp_rmb(); /* read head before q[]. */
- p = CMM_LOAD_SHARED(queue->q[i++ & DEFER_QUEUE_MASK]);
- if (unlikely(DQ_IS_FCT_BIT(p))) {
- DQ_CLEAR_FCT_BIT(p);
- queue->last_fct_out = p;
- p = CMM_LOAD_SHARED(queue->q[i++ & DEFER_QUEUE_MASK]);
- } else if (unlikely(p == DQ_FCT_MARK)) {
- p = CMM_LOAD_SHARED(queue->q[i++ & DEFER_QUEUE_MASK]);
- queue->last_fct_out = p;
- p = CMM_LOAD_SHARED(queue->q[i++ & DEFER_QUEUE_MASK]);
- }
- fct = queue->last_fct_out;
- fct(p);
- }
- cmm_smp_mb(); /* push tail after having used q[] */
- CMM_STORE_SHARED(queue->tail, i);
-}
-
-static void _rcu_defer_barrier_thread(void)
-{
- unsigned long head, num_items;
-
- head = defer_queue.head;
- num_items = head - defer_queue.tail;
- if (unlikely(!num_items))
- return;
- synchronize_rcu();
- rcu_defer_barrier_queue(&defer_queue, head);
-}
-
-void rcu_defer_barrier_thread(void)
-{
- mutex_lock(&rcu_defer_mutex);
- _rcu_defer_barrier_thread();
- mutex_unlock(&rcu_defer_mutex);
-}
-
-/*
- * rcu_defer_barrier - Execute all queued rcu callbacks.
- *
- * Execute all RCU callbacks queued before rcu_defer_barrier() execution.
- * All callbacks queued on the local thread prior to a rcu_defer_barrier() call
- * are guaranteed to be executed.
- * Callbacks queued by other threads concurrently with rcu_defer_barrier()
- * execution are not guaranteed to be executed in the current batch (could
- * be left for the next batch). These callbacks queued by other threads are only
- * guaranteed to be executed if there is explicit synchronization between
- * the thread adding to the queue and the thread issuing the defer_barrier call.
- */
-
-void rcu_defer_barrier(void)
-{
- struct defer_queue *index;
- unsigned long num_items = 0;
-
- if (cds_list_empty(®istry))
- return;
-
- mutex_lock(&rcu_defer_mutex);
- cds_list_for_each_entry(index, ®istry, list) {
- index->last_head = CMM_LOAD_SHARED(index->head);
- num_items += index->last_head - index->tail;
- }
- if (likely(!num_items)) {
- /*
- * We skip the grace period because there are no queued
- * callbacks to execute.
- */
- goto end;
- }
- synchronize_rcu();
- cds_list_for_each_entry(index, ®istry, list)
- rcu_defer_barrier_queue(index, index->last_head);
-end:
- mutex_unlock(&rcu_defer_mutex);
-}
-
-/*
- * _defer_rcu - Queue a RCU callback.
- */
-void _defer_rcu(void (*fct)(void *p), void *p)
-{
- unsigned long head, tail;
-
- /*
- * Head is only modified by ourself. Tail can be modified by reclamation
- * thread.
- */
- head = defer_queue.head;
- tail = CMM_LOAD_SHARED(defer_queue.tail);
-
- /*
- * If queue is full, or reached threshold. Empty queue ourself.
- * Worse-case: must allow 2 supplementary entries for fct pointer.
- */
- if (unlikely(head - tail >= DEFER_QUEUE_SIZE - 2)) {
- assert(head - tail <= DEFER_QUEUE_SIZE);
- rcu_defer_barrier_thread();
- assert(head - CMM_LOAD_SHARED(defer_queue.tail) == 0);
- }
-
- if (unlikely(defer_queue.last_fct_in != fct)) {
- defer_queue.last_fct_in = fct;
- if (unlikely(DQ_IS_FCT_BIT(fct) || fct == DQ_FCT_MARK)) {
- /*
- * If the function to encode is not aligned or the
- * marker, write DQ_FCT_MARK followed by the function
- * pointer.
- */
- _CMM_STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK],
- DQ_FCT_MARK);
- _CMM_STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK],
- fct);
- } else {
- DQ_SET_FCT_BIT(fct);
- _CMM_STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK],
- fct);
- }
- } else {
- if (unlikely(DQ_IS_FCT_BIT(p) || p == DQ_FCT_MARK)) {
- /*
- * If the data to encode is not aligned or the marker,
- * write DQ_FCT_MARK followed by the function pointer.
- */
- _CMM_STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK],
- DQ_FCT_MARK);
- _CMM_STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK],
- fct);
- }
- }
- _CMM_STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK], p);
- cmm_smp_wmb(); /* Publish new pointer before head */
- /* Write q[] before head. */
- CMM_STORE_SHARED(defer_queue.head, head);
- cmm_smp_mb(); /* Write queue head before read futex */
- /*
- * Wake-up any waiting defer thread.
- */
- wake_up_defer();
-}
-
-void *thr_defer(void *args)
-{
- for (;;) {
- pthread_testcancel();
- /*
- * "Be green". Don't wake up the CPU if there is no RCU work
- * to perform whatsoever. Aims at saving laptop battery life by
- * leaving the processor in sleep state when idle.
- */
- wait_defer();
- /* Sleeping after wait_defer to let many callbacks enqueue */
- poll(NULL,0,100); /* wait for 100ms */
- rcu_defer_barrier();
- }
-
- return NULL;
-}
-
-/*
- * library wrappers to be used by non-LGPL compatible source code.
- */
-
-void defer_rcu(void (*fct)(void *p), void *p)
-{
- _defer_rcu(fct, p);
-}
-
-static void start_defer_thread(void)
-{
- int ret;
-
- ret = pthread_create(&tid_defer, NULL, thr_defer, NULL);
- assert(!ret);
-}
-
-static void stop_defer_thread(void)
-{
- int ret;
- void *tret;
-
- pthread_cancel(tid_defer);
- wake_up_defer();
- ret = pthread_join(tid_defer, &tret);
- assert(!ret);
-}
-
-int rcu_defer_register_thread(void)
-{
- int was_empty;
-
- assert(defer_queue.last_head == 0);
- assert(defer_queue.q == NULL);
- defer_queue.q = malloc(sizeof(void *) * DEFER_QUEUE_SIZE);
- if (!defer_queue.q)
- return -ENOMEM;
-
- mutex_lock(&defer_thread_mutex);
- mutex_lock(&rcu_defer_mutex);
- was_empty = cds_list_empty(®istry);
- cds_list_add(&defer_queue.list, ®istry);
- mutex_unlock(&rcu_defer_mutex);
-
- if (was_empty)
- start_defer_thread();
- mutex_unlock(&defer_thread_mutex);
- return 0;
-}
-
-void rcu_defer_unregister_thread(void)
-{
- int is_empty;
-
- mutex_lock(&defer_thread_mutex);
- mutex_lock(&rcu_defer_mutex);
- cds_list_del(&defer_queue.list);
- _rcu_defer_barrier_thread();
- free(defer_queue.q);
- defer_queue.q = NULL;
- is_empty = cds_list_empty(®istry);
- mutex_unlock(&rcu_defer_mutex);
-
- if (is_empty)
- stop_defer_thread();
- mutex_unlock(&defer_thread_mutex);
-}
-
-void rcu_defer_exit(void)
-{
- assert(cds_list_empty(®istry));
-}
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