From: Mathieu Desnoyers Date: Fri, 21 Jun 2013 17:59:09 +0000 (-0400) Subject: doc/examples: cds_list_replace_rcu X-Git-Tag: v0.8.0~55 X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=7eba9f8868d01401bc9b09ab2764bd371b783ad1;p=userspace-rcu.git doc/examples: cds_list_replace_rcu Signed-off-by: Mathieu Desnoyers --- diff --git a/.gitignore b/.gitignore index c4c3bdd..411fd22 100644 --- a/.gitignore +++ b/.gitignore @@ -76,6 +76,7 @@ tests/*.log doc/examples/list/cds_list_add_rcu doc/examples/list/cds_list_add_tail_rcu doc/examples/list/cds_list_del_rcu +doc/examples/list/cds_list_replace_rcu #automake /config.h diff --git a/doc/examples/Makefile.am b/doc/examples/Makefile.am index cae3a02..f80ebeb 100644 --- a/doc/examples/Makefile.am +++ b/doc/examples/Makefile.am @@ -16,9 +16,11 @@ dist_doc_examples_list_DATA = \ list/Makefile.cds_list_add_rcu \ list/Makefile.cds_list_add_tail_rcu \ list/Makefile.cds_list_del_rcu \ + list/Makefile.cds_list_replace_rcu \ list/cds_list_add_rcu.c \ list/cds_list_add_tail_rcu.c \ - list/cds_list_del_rcu.c + list/cds_list_del_rcu.c \ + list/cds_list_replace_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 7507650..efd8a04 100644 --- a/doc/examples/list/Makefile +++ b/doc/examples/list/Makefile @@ -15,9 +15,11 @@ all: $(MAKE) -f Makefile.cds_list_add_rcu $(MAKE) -f Makefile.cds_list_add_tail_rcu $(MAKE) -f Makefile.cds_list_del_rcu + $(MAKE) -f Makefile.cds_list_replace_rcu .PHONY: clean clean: $(MAKE) -f Makefile.cds_list_add_rcu clean $(MAKE) -f Makefile.cds_list_add_tail_rcu clean $(MAKE) -f Makefile.cds_list_del_rcu clean + $(MAKE) -f Makefile.cds_list_replace_rcu clean diff --git a/doc/examples/list/Makefile.cds_list_replace_rcu b/doc/examples/list/Makefile.cds_list_replace_rcu new file mode 100644 index 0000000..a22109f --- /dev/null +++ b/doc/examples/list/Makefile.cds_list_replace_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_replace_rcu + +SOURCES = $(EXAMPLE_NAME).c +OBJECTS = $(EXAMPLE_NAME).o +BINARY = $(EXAMPLE_NAME) + +include ../Makefile.examples.template diff --git a/doc/examples/list/cds_list_replace_rcu.c b/doc/examples/list/cds_list_replace_rcu.c new file mode 100644 index 0000000..4ccc1df --- /dev/null +++ b/doc/examples/list/cds_list_replace_rcu.c @@ -0,0 +1,94 @@ +/* + * 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 replace a node within 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_tail_rcu(&node->node, &mylist); + } + + /* + * Replacing all values by their negated value. Safe against + * concurrent RCU traversals, require mutual exclusion with list + * updates. Notice the "safe" iteration: it is safe against + * removal (and thus replacement) of nodes as we iterate on the + * list. + */ + cds_list_for_each_entry_safe(node, n, &mylist, node) { + struct mynode *new_node; + + new_node = malloc(sizeof(*node)); + if (!new_node) { + ret = -1; + goto end; + } + /* Replacement node value is negated original value. */ + new_node->value = -node->value; + cds_list_replace_rcu(&node->node, &new_node->node); + 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; +}