lib: extract drmtest_permute_array

Lots of tests need to create havoc to LRUs in the kernel or otherwise
need to shuffle things around a bit. So make a small array permutation
function available.

Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

2 files changed, 20 insertions, 0 deletions

diff --git a/lib/drmtest.c b/lib/drmtest.c
index 521a38a2..cc946411 100644
--- a/lib/drmtest.c
+++ b/lib/drmtest.c
@@ -332,6 +332,22 @@ void drmtest_stop_signal_helper(void)
 	signal_helper = -1;
 }
 
+/* other helpers */
+void drmtest_permute_array(void *array, unsigned size,
+			   void (*exchange_func)(void *array,
+						 unsigned i,
+						 unsigned j))
+{
+	int i;
+
+	for (i = size - 1; i > 1; i--) {
+		/* yes, not perfectly uniform, who cares */
+		long l = random() % (i +1);
+		if (i != l)
+			exchange_func(array, i, l);
+	}
+}
+
 /* mappable aperture trasher helper */
 drm_intel_bo **trash_bos;
 int num_trash_bos;
diff --git a/lib/drmtest.h b/lib/drmtest.h
index 3a3bc9aa..23d6f089 100644
--- a/lib/drmtest.h
+++ b/lib/drmtest.h
@@ -55,6 +55,10 @@ uint64_t gem_mappable_aperture_size(void);
 /* generally useful helpers */
 void drmtest_fork_signal_helper(void);
 void drmtest_stop_signal_helper(void);
+void drmtest_permute_array(void *array, unsigned size,
+			   void (*exchange_func)(void *array,
+						 unsigned i,
+						 unsigned j));
 
 /* helpers based upon the libdrm buffer manager */
 void drmtest_init_aperture_trashers(drm_intel_bufmgr *bufmgr);