cregit-Linux how code gets into the kernel

Release 4.9 tools/testing/radix-tree/iteration_check.c

/*
 * iteration_check.c: test races having to do with radix tree iteration
 * Copyright (c) 2016 Intel Corporation
 * Author: Ross Zwisler <ross.zwisler@linux.intel.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 */
#include <linux/radix-tree.h>
#include <pthread.h>
#include "test.h"


#define NUM_THREADS 4

#define TAG 0

static pthread_mutex_t tree_lock = PTHREAD_MUTEX_INITIALIZER;

static pthread_t threads[NUM_THREADS];
RADIX_TREE(tree, GFP_KERNEL);

bool test_complete;

/* relentlessly fill the tree with tagged entries */

static void *add_entries_fn(void *arg) { int pgoff; while (!test_complete) { for (pgoff = 0; pgoff < 100; pgoff++) { pthread_mutex_lock(&tree_lock); if (item_insert(&tree, pgoff) == 0) item_tag_set(&tree, pgoff, TAG); pthread_mutex_unlock(&tree_lock); } } return NULL; }

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/* * Iterate over the tagged entries, doing a radix_tree_iter_retry() as we find * things that have been removed and randomly resetting our iteration to the * next chunk with radix_tree_iter_next(). Both radix_tree_iter_retry() and * radix_tree_iter_next() cause radix_tree_next_slot() to be called with a * NULL 'slot' variable. */
static void *tagged_iteration_fn(void *arg) { struct radix_tree_iter iter; void **slot; while (!test_complete) { rcu_read_lock(); radix_tree_for_each_tagged(slot, &tree, &iter, 0, TAG) { void *entry; int i; /* busy wait to let removals happen */ for (i = 0; i < 1000000; i++) ; entry = radix_tree_deref_slot(slot); if (unlikely(!entry)) continue; if (radix_tree_deref_retry(entry)) { slot = radix_tree_iter_retry(&iter); continue; } if (rand() % 50 == 0) slot = radix_tree_iter_next(&iter); } rcu_read_unlock(); } return NULL; }

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/* * Iterate over the entries, doing a radix_tree_iter_retry() as we find things * that have been removed and randomly resetting our iteration to the next * chunk with radix_tree_iter_next(). Both radix_tree_iter_retry() and * radix_tree_iter_next() cause radix_tree_next_slot() to be called with a * NULL 'slot' variable. */
static void *untagged_iteration_fn(void *arg) { struct radix_tree_iter iter; void **slot; while (!test_complete) { rcu_read_lock(); radix_tree_for_each_slot(slot, &tree, &iter, 0) { void *entry; int i; /* busy wait to let removals happen */ for (i = 0; i < 1000000; i++) ; entry = radix_tree_deref_slot(slot); if (unlikely(!entry)) continue; if (radix_tree_deref_retry(entry)) { slot = radix_tree_iter_retry(&iter); continue; } if (rand() % 50 == 0) slot = radix_tree_iter_next(&iter); } rcu_read_unlock(); } return NULL; }

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/* * Randomly remove entries to help induce radix_tree_iter_retry() calls in the * two iteration functions. */
static void *remove_entries_fn(void *arg) { while (!test_complete) { int pgoff; pgoff = rand() % 100; pthread_mutex_lock(&tree_lock); item_delete(&tree, pgoff); pthread_mutex_unlock(&tree_lock); } return NULL; }

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/* This is a unit test for a bug found by the syzkaller tester */
void iteration_test(void) { int i; printf("Running iteration tests for 10 seconds\n"); srand(time(0)); test_complete = false; if (pthread_create(&threads[0], NULL, tagged_iteration_fn, NULL)) { perror("pthread_create"); exit(1); } if (pthread_create(&threads[1], NULL, untagged_iteration_fn, NULL)) { perror("pthread_create"); exit(1); } if (pthread_create(&threads[2], NULL, add_entries_fn, NULL)) { perror("pthread_create"); exit(1); } if (pthread_create(&threads[3], NULL, remove_entries_fn, NULL)) { perror("pthread_create"); exit(1); } sleep(10); test_complete = true; for (i = 0; i < NUM_THREADS; i++) { if (pthread_join(threads[i], NULL)) { perror("pthread_join"); exit(1); } } item_kill_tree(&tree); }

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