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/[email protected]
Signed-off-by: Matthew Wilcox <[email protected]>
Tested-by: Kirill A. Shutemov <[email protected]>
Cc: Konstantin Khlebnikov <[email protected]>
Cc: Ross Zwisler <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 7 insertions, 4 deletions

diff --git a/tools/testing/radix-tree/iteration_check.c b/tools/testing/radix-tree/iteration_check.c
index 9adb8e7415a6..11d570c3fc83 100644
--- 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);