doc/examples: cds_lfht_destroy
authorMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Sun, 23 Jun 2013 18:38:10 +0000 (14:38 -0400)
committerMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Sun, 23 Jun 2013 18:38:10 +0000 (14:38 -0400)
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
.gitignore
doc/examples/Makefile.am
doc/examples/rculfhash/Makefile
doc/examples/rculfhash/Makefile.cds_lfht_destroy [new file with mode: 0644]
doc/examples/rculfhash/cds_lfht_destroy.c [new file with mode: 0644]

index 9767ac3d935462b92c69e2e31b2ff2deb48f6bb9..bca252aa872177e971f7b275e43954b435be4e59 100644 (file)
@@ -110,6 +110,7 @@ doc/examples/rculfhash/cds_lfht_add
 doc/examples/rculfhash/cds_lfht_add_unique
 doc/examples/rculfhash/cds_lfht_add_replace
 doc/examples/rculfhash/cds_lfht_del
+doc/examples/rculfhash/cds_lfht_destroy
 
 #automake
 /config.h
index bf1901691e7b5d034a2cba529a3bf8cdbe12251f..31bac6d9544ced6ed4244dc8ce4658cb42e1bc1f 100644 (file)
@@ -100,10 +100,12 @@ dist_doc_examples_rculfhash_DATA = \
        rculfhash/Makefile.cds_lfht_add_unique \
        rculfhash/Makefile.cds_lfht_add_replace \
        rculfhash/Makefile.cds_lfht_del \
+       rculfhash/Makefile.cds_lfht_destroy \
        rculfhash/cds_lfht_add.c \
        rculfhash/cds_lfht_add_unique.c \
        rculfhash/cds_lfht_add_replace.c \
-       rculfhash/cds_lfht_del.c
+       rculfhash/cds_lfht_del.c \
+       rculfhash/cds_lfht_destroy.c
 
 if NO_SHARED
 # Don't build examples if shared libraries support was explicitly
index 52da73791bab60de74a15a1ffc5c1cb3d2cca7f0..d7918eed306ab082431ec2da88dadb5053bb6ba3 100644 (file)
@@ -16,6 +16,7 @@ all:
        $(MAKE) -f Makefile.cds_lfht_add_unique
        $(MAKE) -f Makefile.cds_lfht_add_replace
        $(MAKE) -f Makefile.cds_lfht_del
+       $(MAKE) -f Makefile.cds_lfht_destroy
 
 .PHONY: clean
 clean:
@@ -23,3 +24,4 @@ clean:
        $(MAKE) -f Makefile.cds_lfht_add_unique clean
        $(MAKE) -f Makefile.cds_lfht_add_replace clean
        $(MAKE) -f Makefile.cds_lfht_del clean
+       $(MAKE) -f Makefile.cds_lfht_destroy clean
diff --git a/doc/examples/rculfhash/Makefile.cds_lfht_destroy b/doc/examples/rculfhash/Makefile.cds_lfht_destroy
new file mode 100644 (file)
index 0000000..d797893
--- /dev/null
@@ -0,0 +1,22 @@
+# Copyright (C) 2013  Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+#
+# 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_lfht_destroy
+
+SOURCES = $(EXAMPLE_NAME).c
+DEPS = jhash.h
+OBJECTS = $(EXAMPLE_NAME).o
+BINARY = $(EXAMPLE_NAME)
+LIBS = -lurcu-cds -lurcu
+
+include ../Makefile.examples.template
diff --git a/doc/examples/rculfhash/cds_lfht_destroy.c b/doc/examples/rculfhash/cds_lfht_destroy.c
new file mode 100644 (file)
index 0000000..d82d81c
--- /dev/null
@@ -0,0 +1,149 @@
+/*
+ * Copyright (C) 2013  Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * 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 use cds_lfht_destroy() to clear memory used
+ * by a a RCU lock-free hash table. This hash table requires using a
+ * RCU scheme.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+#include <urcu.h>              /* RCU flavor */
+#include <urcu/rculfhash.h>    /* RCU Lock-free hash table */
+#include <urcu/compiler.h>     /* For CAA_ARRAY_SIZE */
+#include "jhash.h"             /* Example hash function */
+
+/*
+ * Nodes populated into the hash table.
+ */
+struct mynode {
+       int value;                      /* Node content */
+       struct cds_lfht_node node;      /* Chaining in hash table */
+       struct rcu_head rcu_head;       /* For call_rcu() */
+};
+
+static
+void free_node(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, 42, 36, 24, }; /* 42 is duplicated */
+       struct cds_lfht *ht;    /* Hash table */
+       unsigned int i;
+       int ret = 0;
+       uint32_t seed;
+       struct cds_lfht_iter iter;      /* For iteration on hash table */
+       struct cds_lfht_node *ht_node;
+       struct mynode *node;
+
+       /*
+        * Each thread need using RCU read-side need to be explicitly
+        * registered.
+        */
+       rcu_register_thread();
+
+       /* Use time as seed for hash table hashing. */
+       seed = (uint32_t) time(NULL);
+
+       /*
+        * Allocate hash table.
+        */
+       ht = cds_lfht_new(1, 1, 0,
+               CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING,
+               NULL);
+       if (!ht) {
+               printf("Error allocating hash table\n");
+               ret = -1;
+               goto end;
+       }
+
+       /*
+        * Add nodes to hash table.
+        */
+       for (i = 0; i < CAA_ARRAY_SIZE(values); i++) {
+               unsigned long hash;
+               int value;
+
+               node = malloc(sizeof(*node));
+               if (!node) {
+                       ret = -1;
+                       goto end;
+               }
+
+               cds_lfht_node_init(&node->node);
+               value = values[i];
+               node->value = value;
+               hash = jhash(&value, sizeof(value), seed);
+
+               /*
+                * cds_lfht_add() needs to be called from RCU read-side
+                * critical section.
+                */
+               rcu_read_lock();
+               cds_lfht_add(ht, hash, &node->node);
+               rcu_read_unlock();
+       }
+
+       /*
+        * Iterate over each hash table node. Those will appear in
+        * random order, depending on the hash seed. Iteration needs to
+        * be performed within RCU read-side critical section.
+        */
+       printf("hash table content (random order):");
+       rcu_read_lock();
+       cds_lfht_for_each_entry(ht, &iter, node, node) {
+               printf(" %d", node->value);
+       }
+       rcu_read_unlock();
+       printf("\n");
+
+
+       /*
+        * Make sure all hash table nodes are removed before destroying.
+        */
+       printf("removing all nodes:");
+       rcu_read_lock();
+       cds_lfht_for_each_entry(ht, &iter, node, node) {
+               ht_node = cds_lfht_iter_get_node(&iter);
+               ret = cds_lfht_del(ht, ht_node);
+               printf(" %d", node->value);
+               if (ret) {
+                       printf(" (concurrently deleted)");
+               } else {
+                       call_rcu(&node->rcu_head, free_node);
+               }
+       }
+       rcu_read_unlock();
+       printf("\n");
+
+       /*
+        * cds_lfht_destroy() must be called from a very specific
+        * context: it needs to be called from a registered RCU reader
+        * thread. However, this thread should _not_ be within a RCU
+        * read-side critical section. Also, it should _not_ be called
+        * from a call_rcu thread.
+        */
+       ret = cds_lfht_destroy(ht, NULL);
+       if (ret) {
+               printf("Destroying hash table failed\n");
+       }
+end:
+       rcu_unregister_thread();
+       return ret;
+}
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