a33d42dd03
When testing, we want a random but yet reproducible order in which to process elements. Here we create an array which is a random (using the Tausworthe PRNG) permutation of the order in which to execute. Note these are simple helpers intended to be merged upstream in lib/ v2: Tidier code by David Herrmann v3: Add reminder that this code is intended to be temporary, with at least the bulk of the prandom changes going to lib/ Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: David Herrmann <dh.herrmann@gmail.com> Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: http://patchwork.freedesktop.org/patch/msgid/20161222083641.2691-6-chris@chris-wilson.co.uk
42 lines
949 B
C
42 lines
949 B
C
#include <linux/bitops.h>
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#include <linux/kernel.h>
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#include <linux/random.h>
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#include <linux/slab.h>
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#include <linux/types.h>
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#include "drm_random.h"
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static inline u32 drm_prandom_u32_max_state(u32 ep_ro, struct rnd_state *state)
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{
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return upper_32_bits((u64)prandom_u32_state(state) * ep_ro);
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}
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void drm_random_reorder(unsigned int *order, unsigned int count,
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struct rnd_state *state)
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{
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unsigned int i, j;
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for (i = 0; i < count; ++i) {
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BUILD_BUG_ON(sizeof(unsigned int) > sizeof(u32));
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j = drm_prandom_u32_max_state(count, state);
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swap(order[i], order[j]);
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}
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}
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EXPORT_SYMBOL(drm_random_reorder);
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unsigned int *drm_random_order(unsigned int count, struct rnd_state *state)
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{
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unsigned int *order, i;
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order = kmalloc_array(count, sizeof(*order), GFP_TEMPORARY);
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if (!order)
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return order;
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for (i = 0; i < count; i++)
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order[i] = i;
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drm_random_reorder(order, count, state);
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return order;
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}
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EXPORT_SYMBOL(drm_random_order);
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