[ltt-dev] [PATCH urcu 4/5] Make defer_rcu() usable from library using multiple URCU implementations
Paul E. McKenney
paulmck at linux.vnet.ibm.com
Thu Jun 2 19:45:03 EDT 2011
Signed-off-by: Paul E. McKenney <paulmck at linux.vnet.ibm.com>
---
Makefile.am | 4 +-
README | 11 +-
tests/Makefile.am | 2 +-
urcu-bp-map.h | 6 +
urcu-bp.c | 1 +
urcu-bp.h | 1 +
urcu-defer-impl.h | 450 +++++++++++++++++++++++++++++++++++++++++++++++++++
urcu-defer-static.h | 108 ------------
urcu-defer.c | 385 -------------------------------------------
urcu-map.h | 26 +++
urcu-qsbr-map.h | 6 +
urcu-qsbr.c | 1 +
urcu-qsbr.h | 1 +
urcu.c | 1 +
urcu.h | 1 +
15 files changed, 501 insertions(+), 503 deletions(-)
create mode 100644 urcu-defer-impl.h
delete mode 100644 urcu-defer-static.h
delete mode 100644 urcu-defer.c
diff --git a/Makefile.am b/Makefile.am
index 4b70644..1589884 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -30,7 +30,7 @@ COMPAT+=compat_futex.c
endif
lib_LTLIBRARIES = liburcu.la liburcu-qsbr.la liburcu-mb.la liburcu-signal.la \
- liburcu-bp.la liburcu-defer.la \
+ liburcu-bp.la \
libwfqueue.la libwfstack.la librculfqueue.la librculfstack.la
liburcu_la_SOURCES = urcu.c urcu-pointer.c $(COMPAT)
@@ -45,8 +45,6 @@ liburcu_signal_la_CFLAGS = -DRCU_SIGNAL
liburcu_bp_la_SOURCES = urcu-bp.c urcu-pointer.c $(COMPAT)
-liburcu_defer_la_SOURCES = urcu-defer.c $(COMPAT)
-
libwfqueue_la_SOURCES = wfqueue.c $(COMPAT)
libwfstack_la_SOURCES = wfstack.c $(COMPAT)
librculfqueue_la_SOURCES = rculfqueue.c $(COMPAT)
diff --git a/README b/README
index 659511f..7d97f19 100644
--- a/README
+++ b/README
@@ -124,16 +124,15 @@ Writing
Usage of liburcu-defer
- * #include <urcu-defer.h>
- * Link with "-lurcu-defer", and also with one of the urcu library
- (either urcu, urcu-bp, urcu-mb or urcu-qsbr).
+ * Follow instructions for either liburcu, liburcu-qsbr,
+ liburcu-mb, liburcu-signal, or liburcu-bp above.
+ The liburcu-defer functionality is pulled into each of
+ those library modules.
* Provides defer_rcu() primitive to enqueue delayed callbacks. Queued
callbacks are executed in batch periodically after a grace period.
Do _not_ use defer_rcu() within a read-side critical section, because
it may call synchronize_rcu() if the thread queue is full.
- * Provides defer_rcu_ratelimit() primitive, which acts just like
- defer_rcu(), but takes an additional rate limiter callback forcing
- synchronized callback execution of the limiter returns non-zero.
+ This can lead to deadlock or worse.
* Requires that rcu_defer_barrier() must be called in library destructor
if a library queues callbacks and is expected to be unloaded with
dlclose().
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 8dacb11..5598689 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -35,7 +35,7 @@ URCU_MB=$(top_srcdir)/urcu.c $(top_srcdir)/urcu-pointer.c $(top_srcdir)/wfqueue.
# URCU_SIGNAL uses urcu.c but -DRCU_SIGNAL must be defined
URCU_SIGNAL=$(top_srcdir)/urcu.c $(top_srcdir)/urcu-pointer.c $(top_srcdir)/wfqueue.c $(COMPAT)
URCU_BP=$(top_srcdir)/urcu-bp.c $(top_srcdir)/urcu-pointer.c $(top_srcdir)/wfqueue.c $(COMPAT)
-URCU_DEFER=$(top_srcdir)/urcu.c $(top_srcdir)/urcu-defer.c $(top_srcdir)/urcu-pointer.c $(top_srcdir)/wfqueue.c $(COMPAT)
+URCU_DEFER=$(top_srcdir)/urcu.c $(top_srcdir)/urcu-pointer.c $(top_srcdir)/wfqueue.c $(COMPAT)
URCU_LIB=$(top_builddir)/liburcu.la
URCU_QSBR_LIB=$(top_builddir)/liburcu-qsbr.la
diff --git a/urcu-bp-map.h b/urcu-bp-map.h
index 6321802..1d77006 100644
--- a/urcu-bp-map.h
+++ b/urcu-bp-map.h
@@ -58,4 +58,10 @@
#define free_all_cpu_call_rcu_data free_all_cpu_call_rcu_data_bp
#define call_rcu call_rcu_bp
+#define defer_rcu defer_rcu_bp
+#define rcu_defer_register_thread rcu_defer_register_thread_bp
+#define rcu_defer_unregister_thread rcu_defer_unregister_thread_bp
+#define rcu_defer_barrier rcu_defer_barrier_bp
+#define rcu_defer_barrier_thread rcu_defer_barrier_thread_bp
+
#endif /* _URCU_BP_MAP_H */
diff --git a/urcu-bp.c b/urcu-bp.c
index 5474f9f..14b2001 100644
--- a/urcu-bp.c
+++ b/urcu-bp.c
@@ -379,3 +379,4 @@ void rcu_bp_after_fork_child(void)
}
#include "urcu-call-rcu-impl.h"
+#include "urcu-defer-impl.h"
diff --git a/urcu-bp.h b/urcu-bp.h
index bc2dbc3..21fe66a 100644
--- a/urcu-bp.h
+++ b/urcu-bp.h
@@ -118,5 +118,6 @@ static inline void rcu_init(void)
#endif
#include "urcu-call-rcu.h"
+#include "urcu-defer.h"
#endif /* _URCU_BP_H */
diff --git a/urcu-defer-impl.h b/urcu-defer-impl.h
new file mode 100644
index 0000000..0aedd53
--- /dev/null
+++ b/urcu-defer-impl.h
@@ -0,0 +1,450 @@
+#ifndef _URCU_DEFER_IMPL_H
+#define _URCU_DEFER_IMPL_H
+
+/*
+ * urcu-defer-impl.h
+ *
+ * Userspace RCU header - memory reclamation.
+ *
+ * TO BE INCLUDED ONLY FROM URCU LIBRARY CODE. See urcu-defer.h for linking
+ * dynamically with the userspace rcu reclamation library.
+ *
+ * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers at 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
+ *
+ * IBM's contributions to this file may be relicensed under LGPLv2 or later.
+ */
+
+#include <stdlib.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <signal.h>
+#include <assert.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/compiler.h>
+#include <urcu/arch.h>
+#include <urcu/uatomic_arch.h>
+#include <urcu/list.h>
+#include <urcu/system.h>
+
+/*
+ * Number of entries in the per-thread defer queue. Must be power of 2.
+ */
+#define DEFER_QUEUE_SIZE (1 << 12)
+#define DEFER_QUEUE_MASK (DEFER_QUEUE_SIZE - 1)
+
+/*
+ * Typically, data is aligned at least on the architecture size.
+ * Use lowest bit to indicate that the current callback is changing.
+ * Assumes that (void *)-2L is not used often. Used to encode non-aligned
+ * functions and non-aligned data using extra space.
+ * We encode the (void *)-2L fct as: -2L, fct, data.
+ * We encode the (void *)-2L data as: -2L, fct, data.
+ * Here, DQ_FCT_MARK == ~DQ_FCT_BIT. Required for the test order.
+ */
+#define DQ_FCT_BIT (1 << 0)
+#define DQ_IS_FCT_BIT(x) ((unsigned long)(x) & DQ_FCT_BIT)
+#define DQ_SET_FCT_BIT(x) \
+ (x = (void *)((unsigned long)(x) | DQ_FCT_BIT))
+#define DQ_CLEAR_FCT_BIT(x) \
+ (x = (void *)((unsigned long)(x) & ~DQ_FCT_BIT))
+#define DQ_FCT_MARK ((void *)(~DQ_FCT_BIT))
+
+/*
+ * This code section can only be included in LGPL 2.1 compatible source code.
+ * See below for the function call wrappers which can be used in code meant to
+ * be only linked with the Userspace RCU library. This comes with a small
+ * performance degradation on the read-side due to the added function calls.
+ * This is required to permit relinking with newer versions of the library.
+ */
+
+#ifdef DEBUG_RCU
+#define rcu_assert(args...) assert(args)
+#else
+#define rcu_assert(args...)
+#endif
+
+/*
+ * defer queue.
+ * Contains pointers. Encoded to save space when same callback is often used.
+ * When looking up the next item:
+ * - if DQ_FCT_BIT is set, set the current callback to DQ_CLEAR_FCT_BIT(ptr)
+ * - next element contains pointer to data.
+ * - else if item == DQ_FCT_MARK
+ * - set the current callback to next element ptr
+ * - following next element contains pointer to data.
+ * - else current element contains data
+ */
+struct defer_queue {
+ unsigned long head; /* add element at head */
+ void *last_fct_in; /* last fct pointer encoded */
+ unsigned long tail; /* next element to remove at tail */
+ void *last_fct_out; /* last fct pointer encoded */
+ void **q;
+ /* registry information */
+ unsigned long last_head;
+ struct cds_list_head list; /* list of thread queues */
+};
+
+/* 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_defer);
+static pthread_t tid_defer;
+
+static void mutex_lock_defer(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 */
+}
+
+/*
+ * 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_defer(&rcu_defer_mutex);
+ cds_list_for_each_entry(index, ®istry_defer, 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_defer(&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_defer))
+ return;
+
+ mutex_lock_defer(&rcu_defer_mutex);
+ cds_list_for_each_entry(index, ®istry_defer, 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_defer, 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(&defer_thread_mutex);
+ mutex_lock_defer(&rcu_defer_mutex);
+ was_empty = cds_list_empty(®istry_defer);
+ cds_list_add(&defer_queue.list, ®istry_defer);
+ 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(&defer_thread_mutex);
+ mutex_lock_defer(&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_defer);
+ 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_defer));
+}
+
+#endif /* _URCU_DEFER_IMPL_H */
diff --git a/urcu-defer-static.h b/urcu-defer-static.h
deleted file mode 100644
index 3e5df3e..0000000
--- a/urcu-defer-static.h
+++ /dev/null
@@ -1,108 +0,0 @@
-#ifndef _URCU_DEFER_STATIC_H
-#define _URCU_DEFER_STATIC_H
-
-/*
- * urcu-defer-static.h
- *
- * Userspace RCU header - memory reclamation.
- *
- * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu-defer.h for linking
- * dynamically with the userspace rcu reclamation library.
- *
- * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers at 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
- *
- * IBM's contributions to this file may be relicensed under LGPLv2 or later.
- */
-
-#include <stdlib.h>
-#include <pthread.h>
-
-#include <urcu/compiler.h>
-#include <urcu/arch.h>
-#include <urcu/uatomic_arch.h>
-#include <urcu/list.h>
-#include <urcu/system.h>
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-/*
- * Number of entries in the per-thread defer queue. Must be power of 2.
- */
-#define DEFER_QUEUE_SIZE (1 << 12)
-#define DEFER_QUEUE_MASK (DEFER_QUEUE_SIZE - 1)
-
-/*
- * Typically, data is aligned at least on the architecture size.
- * Use lowest bit to indicate that the current callback is changing.
- * Assumes that (void *)-2L is not used often. Used to encode non-aligned
- * functions and non-aligned data using extra space.
- * We encode the (void *)-2L fct as: -2L, fct, data.
- * We encode the (void *)-2L data as: -2L, fct, data.
- * Here, DQ_FCT_MARK == ~DQ_FCT_BIT. Required for the test order.
- */
-#define DQ_FCT_BIT (1 << 0)
-#define DQ_IS_FCT_BIT(x) ((unsigned long)(x) & DQ_FCT_BIT)
-#define DQ_SET_FCT_BIT(x) \
- (x = (void *)((unsigned long)(x) | DQ_FCT_BIT))
-#define DQ_CLEAR_FCT_BIT(x) \
- (x = (void *)((unsigned long)(x) & ~DQ_FCT_BIT))
-#define DQ_FCT_MARK ((void *)(~DQ_FCT_BIT))
-
-/*
- * This code section can only be included in LGPL 2.1 compatible source code.
- * See below for the function call wrappers which can be used in code meant to
- * be only linked with the Userspace RCU library. This comes with a small
- * performance degradation on the read-side due to the added function calls.
- * This is required to permit relinking with newer versions of the library.
- */
-
-#ifdef DEBUG_RCU
-#define rcu_assert(args...) assert(args)
-#else
-#define rcu_assert(args...)
-#endif
-
-/*
- * defer queue.
- * Contains pointers. Encoded to save space when same callback is often used.
- * When looking up the next item:
- * - if DQ_FCT_BIT is set, set the current callback to DQ_CLEAR_FCT_BIT(ptr)
- * - next element contains pointer to data.
- * - else if item == DQ_FCT_MARK
- * - set the current callback to next element ptr
- * - following next element contains pointer to data.
- * - else current element contains data
- */
-struct defer_queue {
- unsigned long head; /* add element at head */
- void *last_fct_in; /* last fct pointer encoded */
- unsigned long tail; /* next element to remove at tail */
- void *last_fct_out; /* last fct pointer encoded */
- void **q;
- /* registry information */
- unsigned long last_head;
- struct cds_list_head list; /* list of thread queues */
-};
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif /* _URCU_DEFER_STATIC_H */
diff --git a/urcu-defer.c b/urcu-defer.c
deleted file mode 100644
index 3f596ae..0000000
--- a/urcu-defer.c
+++ /dev/null
@@ -1,385 +0,0 @@
-/*
- * urcu-defer.c
- *
- * Userspace RCU library - batch memory reclamation
- *
- * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers at 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));
-}
diff --git a/urcu-map.h b/urcu-map.h
index eccaac2..93ac65c 100644
--- a/urcu-map.h
+++ b/urcu-map.h
@@ -34,6 +34,10 @@
/* Mapping macros to allow multiple flavors in a single binary. */
+#if !defined(RCU_MEMBARRIER) && !defined(RCU_SIGNAL) && !defined(RCU_MB)
+#define RCU_MB
+#endif
+
#ifdef RCU_MEMBARRIER
#define rcu_read_lock rcu_read_lock_memb
@@ -60,6 +64,12 @@
#define free_all_cpu_call_rcu_data free_all_cpu_call_rcu_data_memb
#define call_rcu call_rcu_memb
+#define defer_rcu defer_rcu_memb
+#define rcu_defer_register_thread rcu_defer_register_thread_memb
+#define rcu_defer_unregister_thread rcu_defer_unregister_thread_memb
+#define rcu_defer_barrier rcu_defer_barrier_memb
+#define rcu_defer_barrier_thread rcu_defer_barrier_thread_memb
+
#elif defined(RCU_SIGNAL)
#define rcu_read_lock rcu_read_lock_sig
@@ -86,6 +96,12 @@
#define free_all_cpu_call_rcu_data free_all_cpu_call_rcu_data_sig
#define call_rcu call_rcu_sig
+#define defer_rcu defer_rcu_sig
+#define rcu_defer_register_thread rcu_defer_register_thread_sig
+#define rcu_defer_unregister_thread rcu_defer_unregister_thread_sig
+#define rcu_defer_barrier rcu_defer_barrier_sig
+#define rcu_defer_barrier_thread rcu_defer_barrier_thread_sig
+
#elif defined(RCU_MB)
#define rcu_read_lock rcu_read_lock_mb
@@ -112,6 +128,16 @@
#define free_all_cpu_call_rcu_data free_all_cpu_call_rcu_data_mb
#define call_rcu call_rcu_mb
+#define defer_rcu defer_rcu_mb
+#define rcu_defer_register_thread rcu_defer_register_thread_mb
+#define rcu_defer_unregister_thread rcu_defer_unregister_thread_mb
+#define rcu_defer_barrier rcu_defer_barrier_mb
+#define rcu_defer_barrier_thread rcu_defer_barrier_thread_mb
+
+#else
+
+#error "Undefined selection"
+
#endif
#endif /* _URCU_MAP_H */
diff --git a/urcu-qsbr-map.h b/urcu-qsbr-map.h
index 2bce1b6..0d88d83 100644
--- a/urcu-qsbr-map.h
+++ b/urcu-qsbr-map.h
@@ -60,4 +60,10 @@
#define create_all_cpu_call_rcu_data create_all_cpu_call_rcu_data_qsbr
#define call_rcu call_rcu_qsbr
+#define defer_rcu defer_rcu_qsbr
+#define rcu_defer_register_thread rcu_defer_register_thread_qsbr
+#define rcu_defer_unregister_thread rcu_defer_unregister_thread_qsbr
+#define rcu_defer_barrier rcu_defer_barrier_qsbr
+#define rcu_defer_barrier_thread rcu_defer_barrier_thread_qsbr
+
#endif /* _URCU_QSBR_MAP_H */
diff --git a/urcu-qsbr.c b/urcu-qsbr.c
index 8dcad33..cf8b5ce 100644
--- a/urcu-qsbr.c
+++ b/urcu-qsbr.c
@@ -334,3 +334,4 @@ void rcu_exit(void)
}
#include "urcu-call-rcu-impl.h"
+#include "urcu-defer-impl.h"
diff --git a/urcu-qsbr.h b/urcu-qsbr.h
index 7ef1bfe..a691c52 100644
--- a/urcu-qsbr.h
+++ b/urcu-qsbr.h
@@ -125,5 +125,6 @@ extern void rcu_unregister_thread(void);
#endif
#include "urcu-call-rcu.h"
+#include "urcu-defer.h"
#endif /* _URCU_QSBR_H */
diff --git a/urcu.c b/urcu.c
index 4ee9e3b..d356f54 100644
--- a/urcu.c
+++ b/urcu.c
@@ -434,3 +434,4 @@ void rcu_exit(void)
#endif /* #ifdef RCU_SIGNAL */
#include "urcu-call-rcu-impl.h"
+#include "urcu-defer-impl.h"
diff --git a/urcu.h b/urcu.h
index 417e609..15c8c38 100644
--- a/urcu.h
+++ b/urcu.h
@@ -111,5 +111,6 @@ extern void rcu_init(void);
#endif
#include "urcu-call-rcu.h"
+#include "urcu-defer.h"
#endif /* _URCU_H */
--
1.7.3.2
More information about the lttng-dev
mailing list