From: Mathieu Desnoyers Date: Sat, 22 Jun 2013 18:18:22 +0000 (-0400) Subject: doc/examples: add membarrier flavor X-Git-Tag: v0.8.0~23 X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=56e47f8d20864a908c6111d38da150a71eaba354;p=urcu.git doc/examples: add membarrier flavor Signed-off-by: Mathieu Desnoyers --- diff --git a/.gitignore b/.gitignore index 149b6f8..c7381aa 100644 --- a/.gitignore +++ b/.gitignore @@ -75,6 +75,7 @@ tests/*.log doc/examples/urcu-flavors/qsbr doc/examples/urcu-flavors/mb +doc/examples/urcu-flavors/membarrier doc/examples/urcu-flavors/signal doc/examples/list/cds_list_add_rcu diff --git a/doc/examples/Makefile.am b/doc/examples/Makefile.am index 0f3129b..e6d6870 100644 --- a/doc/examples/Makefile.am +++ b/doc/examples/Makefile.am @@ -6,9 +6,11 @@ dist_doc_examples_urcu_flavors_DATA = \ urcu-flavors/Makefile \ urcu-flavors/Makefile.qsbr \ urcu-flavors/Makefile.mb \ + urcu-flavors/Makefile.membarrier \ urcu-flavors/Makefile.signal \ urcu-flavors/qsbr.c \ urcu-flavors/mb.c \ + urcu-flavors/membarrier.c \ urcu-flavors/signal.c dist_doc_examples_DATA = \ diff --git a/doc/examples/urcu-flavors/Makefile b/doc/examples/urcu-flavors/Makefile index e7ada0f..db90df4 100644 --- a/doc/examples/urcu-flavors/Makefile +++ b/doc/examples/urcu-flavors/Makefile @@ -14,10 +14,12 @@ all: $(MAKE) -f Makefile.qsbr $(MAKE) -f Makefile.mb + $(MAKE) -f Makefile.membarrier $(MAKE) -f Makefile.signal .PHONY: clean clean: $(MAKE) -f Makefile.qsbr clean $(MAKE) -f Makefile.mb clean + $(MAKE) -f Makefile.membarrier clean $(MAKE) -f Makefile.signal clean diff --git a/doc/examples/urcu-flavors/Makefile.membarrier b/doc/examples/urcu-flavors/Makefile.membarrier new file mode 100644 index 0000000..977078e --- /dev/null +++ b/doc/examples/urcu-flavors/Makefile.membarrier @@ -0,0 +1,21 @@ +# Copyright (C) 2013 Mathieu Desnoyers +# +# THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED +# OR IMPLIED. ANY USE IS AT YOUR OWN RISK. +# +# Permission is hereby granted to use or copy this program for any +# purpose, provided the above notices are retained on all copies. +# Permission to modify the code and to distribute modified code is +# granted, provided the above notices are retained, and a notice that +# the code was modified is included with the above copyright notice. +# +# This makefile is purposefully kept simple to support GNU and BSD make. + +EXAMPLE_NAME = membarrier + +SOURCES = $(EXAMPLE_NAME).c +OBJECTS = $(EXAMPLE_NAME).o +BINARY = $(EXAMPLE_NAME) +LIBS = -lurcu + +include ../Makefile.examples.template diff --git a/doc/examples/urcu-flavors/membarrier.c b/doc/examples/urcu-flavors/membarrier.c new file mode 100644 index 0000000..0c5be4c --- /dev/null +++ b/doc/examples/urcu-flavors/membarrier.c @@ -0,0 +1,131 @@ +/* + * Copyright (C) 2013 Mathieu Desnoyers + * + * 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 +#include +#include +#include +#include + +#include /* Default: sys_membarrier() RCU flavor */ +#include /* List example */ +#include /* For CAA_ARRAY_SIZE */ + +/* + * Example showing how to use the sys_membarrier()-based Userspace RCU + * flavor. + * + * This is a mock-up example where updates and RCU traversals are + * performed by the same thread to keep things simple on purpose. + */ + +static CDS_LIST_HEAD(mylist); + +struct mynode { + uint64_t value; + struct cds_list_head node; /* linked-list chaining */ + struct rcu_head rcu_head; /* for call_rcu() */ +}; + +static +int add_node(uint64_t v) +{ + struct mynode *node; + + node = calloc(sizeof(*node), 1); + if (!node) + return -1; + node->value = v; + cds_list_add_rcu(&node->node, &mylist); + return 0; +} + +static +void rcu_free_node(struct rcu_head *rh) +{ + struct mynode *node = caa_container_of(rh, struct mynode, rcu_head); + + free(node); +} + +int main(int argc, char **argv) +{ + uint64_t values[] = { 42, 36, 24, }; + unsigned int i; + int ret; + struct mynode *node, *n; + + /* + * Each thread need using RCU read-side need to be explicitly + * registered. + */ + rcu_register_thread(); + + /* + * Adding nodes to the linked-list. Safe against concurrent + * RCU traversals, require mutual exclusion with list updates. + */ + for (i = 0; i < CAA_ARRAY_SIZE(values); i++) { + ret = add_node(values[i]); + if (ret) + goto end; + } + + /* + * We need to explicitly mark RCU read-side critical sections + * with rcu_read_lock() and rcu_read_unlock(). They can be + * nested. Those are no-ops for the QSBR flavor. + */ + rcu_read_lock(); + + /* + * RCU traversal of the linked list. + */ + cds_list_for_each_entry_rcu(node, &mylist, node) { + printf("Value: %" PRIu64 "\n", node->value); + } + rcu_read_unlock(); + + /* + * Removing nodes from linked list. Safe against concurrent RCU + * traversals, require mutual exclusion with list updates. + */ + cds_list_for_each_entry_safe(node, n, &mylist, node) { + cds_list_del_rcu(&node->node); + /* + * call_rcu() will ensure that the handler + * "rcu_free_node" is executed after a grace period. + * call_rcu() can be called from RCU read-side critical + * sections. + */ + call_rcu(&node->rcu_head, rcu_free_node); + } + + sleep(1); + + /* + * Waiting for previously called call_rcu handlers to complete + * before program exits, or in library destructors, is a good + * practice. + */ + rcu_barrier(); + +end: + rcu_unregister_thread(); + return ret; +}