Make defer_rcu() usable from library using multiple URCU implementations
authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Fri, 3 Jun 2011 16:47:56 +0000 (12:47 -0400)
committerMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fri, 3 Jun 2011 16:47:56 +0000 (12:47 -0400)
[ Edit: minor tab to whitespace cleanup ]

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
15 files changed:
Makefile.am
README
tests/Makefile.am
urcu-bp-map.h
urcu-bp.c
urcu-bp.h
urcu-defer-impl.h [new file with mode: 0644]
urcu-defer-static.h [deleted file]
urcu-defer.c [deleted file]
urcu-map.h
urcu-qsbr-map.h
urcu-qsbr.c
urcu-qsbr.h
urcu.c
urcu.h

index 4b70644..1589884 100644 (file)
@@ -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 (file)
--- 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().
index 8dacb11..5598689 100644 (file)
@@ -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
index 6321802..4abe8dc 100644 (file)
 #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 */
index 5474f9f..14b2001 100644 (file)
--- 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"
index bc2dbc3..21fe66a 100644 (file)
--- 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 (file)
index 0000000..0aedd53
--- /dev/null
@@ -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@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, &registry_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(&registry_defer))
+               return;
+
+       mutex_lock_defer(&rcu_defer_mutex);
+       cds_list_for_each_entry(index, &registry_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, &registry_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(&registry_defer);
+       cds_list_add(&defer_queue.list, &registry_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(&registry_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(&registry_defer));
+}
+
+#endif /* _URCU_DEFER_IMPL_H */
diff --git a/urcu-defer-static.h b/urcu-defer-static.h
deleted file mode 100644 (file)
index 3e5df3e..0000000
+++ /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@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 (file)
index 3f596ae..0000000
+++ /dev/null
@@ -1,385 +0,0 @@
-/*
- * 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, &registry, 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(&registry))
-               return;
-
-       mutex_lock(&rcu_defer_mutex);
-       cds_list_for_each_entry(index, &registry, 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, &registry, 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(&registry);
-       cds_list_add(&defer_queue.list, &registry);
-       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(&registry);
-       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(&registry));
-}
index eccaac2..b55e304 100644 (file)
 
 /* 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
 #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
 #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
 #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 */
index 2bce1b6..0d88d83 100644 (file)
 #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 */
index 8dcad33..cf8b5ce 100644 (file)
@@ -334,3 +334,4 @@ void rcu_exit(void)
 }
 
 #include "urcu-call-rcu-impl.h"
+#include "urcu-defer-impl.h"
index 7ef1bfe..a691c52 100644 (file)
@@ -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 (file)
--- 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 (file)
--- 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 */
This page took 0.056758 seconds and 4 git commands to generate.