From: Mathieu Desnoyers Date: Fri, 21 Jun 2013 16:01:06 +0000 (-0400) Subject: doc/examples: cds_list_del_rcu X-Git-Tag: v0.8.0~57 X-Git-Url: https://git.lttng.org/?p=urcu.git;a=commitdiff_plain;h=06ced8d6ec9084d8ebbbd9425f0ad2ba5e249e53 doc/examples: cds_list_del_rcu Signed-off-by: Mathieu Desnoyers --- diff --git a/.gitignore b/.gitignore index 2fdfc1c..ebacc52 100644 --- a/.gitignore +++ b/.gitignore @@ -74,6 +74,7 @@ tests/*.log *.so doc/examples/list/cds_list_add_rcu +doc/examples/list/cds_list_del_rcu #automake /config.h diff --git a/doc/examples/Makefile.am b/doc/examples/Makefile.am index c06a816..1d81287 100644 --- a/doc/examples/Makefile.am +++ b/doc/examples/Makefile.am @@ -14,7 +14,9 @@ doc_examples_listdir = ${doc_examplesdir}/list dist_doc_examples_list_DATA = \ list/Makefile \ list/Makefile.cds_list_add_rcu \ - list/cds_list_add_rcu.c + list/Makefile.cds_list_del_rcu \ + list/cds_list_add_rcu.c \ + list/cds_list_del_rcu.c if NO_SHARED # Don't build examples if shared libraries support was explicitly diff --git a/doc/examples/list/Makefile b/doc/examples/list/Makefile index 122417d..8e2279e 100644 --- a/doc/examples/list/Makefile +++ b/doc/examples/list/Makefile @@ -11,4 +11,11 @@ # # This makefile is purposefully kept simple to support GNU and BSD make. -include Makefile.cds_list_add_rcu +all: + $(MAKE) -f Makefile.cds_list_add_rcu + $(MAKE) -f Makefile.cds_list_del_rcu + +.PHONY: clean +clean: + $(MAKE) -f Makefile.cds_list_add_rcu clean + $(MAKE) -f Makefile.cds_list_del_rcu clean diff --git a/doc/examples/list/Makefile.cds_list_del_rcu b/doc/examples/list/Makefile.cds_list_del_rcu new file mode 100644 index 0000000..5a02b56 --- /dev/null +++ b/doc/examples/list/Makefile.cds_list_del_rcu @@ -0,0 +1,20 @@ +# 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 = cds_list_del_rcu + +SOURCES = $(EXAMPLE_NAME).c +OBJECTS = $(EXAMPLE_NAME).o +BINARY = $(EXAMPLE_NAME) + +include ../Makefile.examples.template diff --git a/doc/examples/list/cds_list_del_rcu.c b/doc/examples/list/cds_list_del_rcu.c new file mode 100644 index 0000000..c355101 --- /dev/null +++ b/doc/examples/list/cds_list_del_rcu.c @@ -0,0 +1,90 @@ +/* + * 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 example shows how to remove from a linked-list safely against + * concurrent RCU traversals. + */ + +#include + +#include /* Userspace RCU flavor */ +#include /* RCU list */ +#include /* For CAA_ARRAY_SIZE */ + +/* + * Nodes populated into the list. + */ +struct mynode { + int value; /* Node content */ + struct cds_list_head node; /* Linked-list chaining */ + struct rcu_head rcu_head; /* For call_rcu() */ +}; + +static +void free_node_rcu(struct rcu_head *head) +{ + struct mynode *node = caa_container_of(head, struct mynode, rcu_head); + + free(node); +} + +int main(int argc, char **argv) +{ + int values[] = { -5, 42, 36, 24, }; + CDS_LIST_HEAD(mylist); /* Defines an empty list head */ + unsigned int i; + int ret = 0; + struct mynode *node, *n; + + /* + * 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++) { + node = malloc(sizeof(*node)); + if (!node) { + ret = -1; + goto end; + } + node->value = values[i]; + cds_list_add_rcu(&node->node, &mylist); + } + + /* + * Removing all positive values. Safe against concurrent RCU + * traversals, require mutual exclusion with list updates. + * Notice the "safe" iteration: it is safe against removal of + * nodes as we iterate on the list. + */ + cds_list_for_each_entry_safe(node, n, &mylist, node) { + if (node->value > 0) { + cds_list_del_rcu(&node->node); + /* + * We can only reclaim memory after a grace + * period has passed after cds_list_del_rcu(). + */ + call_rcu(&node->rcu_head, free_node_rcu); + } + } + + /* + * Just show the list content. This is _not_ an RCU-safe + * iteration on the list. + */ + printf("mylist content:"); + cds_list_for_each_entry(node, &mylist, node) { + printf(" %d", node->value); + } + printf("\n"); +end: + return ret; +}