8331de75cb
While commitc0c09bfdc4
("rhashtable: avoid unnecessary wakeup for worker queue") rightfully moved part of the decision making of whether we should expand or shrink from the expand/shrink functions themselves into insert/delete functions in order to avoid unnecessary worker wake-ups, it however introduced a regression by doing so. Before that change, if no max_shift was specified (= 0) on rhashtable initialization, rhashtable_expand() would just grow unconditionally and lets the available memory be the limiting factor. After that change, if no max_shift was specified, there would be _no_ expansion step at all. Given that netlink and tipc have a max_shift specified, it was not visible there, but Josh Hunt reported that if nft that starts out with a default element hint of 3 if not otherwise provided, would slow i.e. inserts down trememdously as it cannot grow larger to relax table occupancy. Given that the test case verifies shrinks/expands manually, we also must remove pointer to the helper functions to explicitly avoid parallel resizing on insertions/deletions. test_bucket_stats() and test_rht_lookup() could also be wrapped around rhashtable mutex to explicitly synchronize a walk from resizing, but I think that defeats the actual test case which intended to have explicit test steps, i.e. 1) inserts, 2) expands, 3) shrinks, 4) deletions, with object verification after each stage. Reported-by: Josh Hunt <johunt@akamai.com> Fixes:c0c09bfdc4
("rhashtable: avoid unnecessary wakeup for worker queue") Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Cc: Ying Xue <ying.xue@windriver.com> Cc: Josh Hunt <johunt@akamai.com> Acked-by: Thomas Graf <tgraf@suug.ch> Signed-off-by: David S. Miller <davem@davemloft.net>
232 lines
5.0 KiB
C
232 lines
5.0 KiB
C
/*
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* Resizable, Scalable, Concurrent Hash Table
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*
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* Copyright (c) 2014 Thomas Graf <tgraf@suug.ch>
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* Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net>
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*
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* Based on the following paper:
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* https://www.usenix.org/legacy/event/atc11/tech/final_files/Triplett.pdf
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*
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* Code partially derived from nft_hash
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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/**************************************************************************
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* Self Test
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**************************************************************************/
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#include <linux/init.h>
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#include <linux/jhash.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/rcupdate.h>
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#include <linux/rhashtable.h>
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#include <linux/slab.h>
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#define TEST_HT_SIZE 8
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#define TEST_ENTRIES 2048
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#define TEST_PTR ((void *) 0xdeadbeef)
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#define TEST_NEXPANDS 4
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struct test_obj {
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void *ptr;
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int value;
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struct rhash_head node;
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};
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static int __init test_rht_lookup(struct rhashtable *ht)
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{
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unsigned int i;
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for (i = 0; i < TEST_ENTRIES * 2; i++) {
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struct test_obj *obj;
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bool expected = !(i % 2);
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u32 key = i;
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obj = rhashtable_lookup(ht, &key);
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if (expected && !obj) {
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pr_warn("Test failed: Could not find key %u\n", key);
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return -ENOENT;
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} else if (!expected && obj) {
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pr_warn("Test failed: Unexpected entry found for key %u\n",
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key);
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return -EEXIST;
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} else if (expected && obj) {
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if (obj->ptr != TEST_PTR || obj->value != i) {
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pr_warn("Test failed: Lookup value mismatch %p!=%p, %u!=%u\n",
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obj->ptr, TEST_PTR, obj->value, i);
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return -EINVAL;
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}
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}
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}
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return 0;
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}
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static void test_bucket_stats(struct rhashtable *ht, bool quiet)
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{
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unsigned int cnt, rcu_cnt, i, total = 0;
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struct rhash_head *pos;
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struct test_obj *obj;
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struct bucket_table *tbl;
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tbl = rht_dereference_rcu(ht->tbl, ht);
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for (i = 0; i < tbl->size; i++) {
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rcu_cnt = cnt = 0;
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if (!quiet)
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pr_info(" [%#4x/%zu]", i, tbl->size);
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rht_for_each_entry_rcu(obj, pos, tbl, i, node) {
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cnt++;
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total++;
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if (!quiet)
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pr_cont(" [%p],", obj);
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}
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rht_for_each_entry_rcu(obj, pos, tbl, i, node)
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rcu_cnt++;
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if (rcu_cnt != cnt)
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pr_warn("Test failed: Chain count mismach %d != %d",
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cnt, rcu_cnt);
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if (!quiet)
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pr_cont("\n [%#x] first element: %p, chain length: %u\n",
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i, tbl->buckets[i], cnt);
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}
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pr_info(" Traversal complete: counted=%u, nelems=%u, entries=%d\n",
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total, atomic_read(&ht->nelems), TEST_ENTRIES);
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if (total != atomic_read(&ht->nelems) || total != TEST_ENTRIES)
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pr_warn("Test failed: Total count mismatch ^^^");
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}
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static int __init test_rhashtable(struct rhashtable *ht)
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{
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struct bucket_table *tbl;
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struct test_obj *obj;
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struct rhash_head *pos, *next;
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int err;
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unsigned int i;
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/*
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* Insertion Test:
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* Insert TEST_ENTRIES into table with all keys even numbers
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*/
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pr_info(" Adding %d keys\n", TEST_ENTRIES);
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for (i = 0; i < TEST_ENTRIES; i++) {
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struct test_obj *obj;
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obj = kzalloc(sizeof(*obj), GFP_KERNEL);
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if (!obj) {
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err = -ENOMEM;
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goto error;
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}
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obj->ptr = TEST_PTR;
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obj->value = i * 2;
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rhashtable_insert(ht, &obj->node);
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}
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rcu_read_lock();
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test_bucket_stats(ht, true);
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test_rht_lookup(ht);
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rcu_read_unlock();
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for (i = 0; i < TEST_NEXPANDS; i++) {
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pr_info(" Table expansion iteration %u...\n", i);
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mutex_lock(&ht->mutex);
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rhashtable_expand(ht);
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mutex_unlock(&ht->mutex);
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rcu_read_lock();
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pr_info(" Verifying lookups...\n");
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test_rht_lookup(ht);
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rcu_read_unlock();
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}
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for (i = 0; i < TEST_NEXPANDS; i++) {
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pr_info(" Table shrinkage iteration %u...\n", i);
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mutex_lock(&ht->mutex);
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rhashtable_shrink(ht);
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mutex_unlock(&ht->mutex);
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rcu_read_lock();
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pr_info(" Verifying lookups...\n");
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test_rht_lookup(ht);
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rcu_read_unlock();
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}
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rcu_read_lock();
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test_bucket_stats(ht, true);
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rcu_read_unlock();
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pr_info(" Deleting %d keys\n", TEST_ENTRIES);
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for (i = 0; i < TEST_ENTRIES; i++) {
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u32 key = i * 2;
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obj = rhashtable_lookup(ht, &key);
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BUG_ON(!obj);
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rhashtable_remove(ht, &obj->node);
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kfree(obj);
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}
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return 0;
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error:
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tbl = rht_dereference_rcu(ht->tbl, ht);
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for (i = 0; i < tbl->size; i++)
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rht_for_each_entry_safe(obj, pos, next, tbl, i, node)
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kfree(obj);
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return err;
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}
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static struct rhashtable ht;
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static int __init test_rht_init(void)
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{
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struct rhashtable_params params = {
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.nelem_hint = TEST_HT_SIZE,
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.head_offset = offsetof(struct test_obj, node),
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.key_offset = offsetof(struct test_obj, value),
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.key_len = sizeof(int),
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.hashfn = jhash,
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.nulls_base = (3U << RHT_BASE_SHIFT),
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};
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int err;
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pr_info("Running resizable hashtable tests...\n");
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err = rhashtable_init(&ht, ¶ms);
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if (err < 0) {
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pr_warn("Test failed: Unable to initialize hashtable: %d\n",
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err);
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return err;
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}
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err = test_rhashtable(&ht);
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rhashtable_destroy(&ht);
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return err;
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}
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static void __exit test_rht_exit(void)
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{
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}
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module_init(test_rht_init);
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module_exit(test_rht_exit);
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MODULE_LICENSE("GPL v2");
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