radix tree test suite: make runs more reproducible

Instead of reseeding the random number generator every time around the
loop in big_gang_check(), seed it at the beginning of execution.  Use
rand_r() and an independent base seed for each thread in
iteration_test() so they don't stomp all over each others state.  Since
this particular test depends on the kernel scheduler, the iteration test
can't be reproduced based purely on the random seed, but at least it
won't pollute the other tests.

Print the seed, and allow the seed to be specified so that a run which
hits a problem can be reproduced.

Link: http://lkml.kernel.org/r/1480369871-5271-41-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/tools/testing/radix-tree/iteration_check.c b/tools/testing/radix-tree/iteration_check.c
index 9adb8e7415a60f08a05f7a767dfa152734954f32..11d570c3fc83c7b8523f91522d987a2c9ffe3f95 100644 (file)
--- a/tools/testing/radix-tree/iteration_check.c
+++ b/tools/testing/radix-tree/iteration_check.c
@@ -20,6 +20,7 @@
 #define TAG 0
 static pthread_mutex_t tree_lock = PTHREAD_MUTEX_INITIALIZER;
 static pthread_t threads[NUM_THREADS];
+static unsigned int seeds[3];
 RADIX_TREE(tree, GFP_KERNEL);
 bool test_complete;
 
@@ -71,7 +72,7 @@ static void *tagged_iteration_fn(void *arg)
                                continue;
                        }
 
-                       if (rand() % 50 == 0)
+                       if (rand_r(&seeds[0]) % 50 == 0)
                                slot = radix_tree_iter_next(&iter);
                }
                rcu_read_unlock();
@@ -111,7 +112,7 @@ static void *untagged_iteration_fn(void *arg)
                                continue;
                        }
 
-                       if (rand() % 50 == 0)
+                       if (rand_r(&seeds[1]) % 50 == 0)
                                slot = radix_tree_iter_next(&iter);
                }
                rcu_read_unlock();
@@ -129,7 +130,7 @@ static void *remove_entries_fn(void *arg)
        while (!test_complete) {
                int pgoff;
 
-               pgoff = rand() % 100;
+               pgoff = rand_r(&seeds[2]) % 100;
 
                pthread_mutex_lock(&tree_lock);
                item_delete(&tree, pgoff);
@@ -146,9 +147,11 @@ void iteration_test(void)
 
        printf("Running iteration tests for 10 seconds\n");
 
-       srand(time(0));
        test_complete = false;
 
+       for (i = 0; i < 3; i++)
+               seeds[i] = rand();
+
        if (pthread_create(&threads[0], NULL, tagged_iteration_fn, NULL)) {
                perror("pthread_create");
                exit(1);

diff --git a/tools/testing/radix-tree/main.c b/tools/testing/radix-tree/main.c
index 52ce1eab0fd37dbd014f98ecef59f88d70aaa549..2eb6949944977f7688c1fffe258dc0f05781e470 100644 (file)
--- a/tools/testing/radix-tree/main.c
+++ b/tools/testing/radix-tree/main.c
@@ -67,7 +67,6 @@ void big_gang_check(bool long_run)
 
        for (i = 0; i < (long_run ? 1000 : 3); i++) {
                __big_gang_check();
-               srand(time(0));
                printf("%d ", i);
                fflush(stdout);
        }
@@ -329,12 +328,18 @@ int main(int argc, char **argv)
 {
        bool long_run = false;
        int opt;
+       unsigned int seed = time(NULL);
 
-       while ((opt = getopt(argc, argv, "l")) != -1) {
+       while ((opt = getopt(argc, argv, "ls:")) != -1) {
                if (opt == 'l')
                        long_run = true;
+               else if (opt == 's')
+                       seed = strtoul(optarg, NULL, 0);
        }
 
+       printf("random seed %u\n", seed);
+       srand(seed);
+
        rcu_register_thread();
        radix_tree_init();