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authorDave Airlie <airlied@redhat.com>2017-01-09 09:55:57 +1000
committerDave Airlie <airlied@redhat.com>2017-01-09 09:55:57 +1000
commit3806a271bf4be375f304e492148edb2507181158 (patch)
treecd1b2410e8a98e63e44c4cee058b2beeb1924cf4 /lib
parenta121103c922847ba5010819a3f250f1f7fc84ab8 (diff)
parent9b8b75de4cb379187c481a5332a12429f31c0887 (diff)
downloadlinux-3806a271bf4be375f304e492148edb2507181158.tar.gz
linux-3806a271bf4be375f304e492148edb2507181158.tar.xz
Merge tag 'drm-misc-next-2016-12-30' of git://anongit.freedesktop.org/git/drm-misc into drm-next
First -misc pull for 4.11: - drm_mm rework + lots of selftests (Chris Wilson) - new connector_list locking+iterators - plenty of kerneldoc updates - format handling rework from Ville - atomic helper changes from Maarten for better plane corner-case handling in drivers, plus the i915 legacy cursor patch that needs this - bridge cleanup from Laurent - plus plenty of small stuff all over - also contains a merge of the 4.10 docs tree so that we could apply the dma-buf kerneldoc patches It's a lot more than usual, but due to the merge window blackout it also covers about 4 weeks, so all in line again on a per-week basis. The more annoying part with no pull request for 4 weeks is managing cross-tree work. The -intel pull request I'll follow up with does conflict quite a bit with -misc here. Longer-term (if drm-misc keeps growing) a drm-next-queued to accept pull request for the next merge window during this time might be useful. I'd also like to backmerge -rc2+this into drm-intel next week, we have quite a pile of patches waiting for the stuff in here. * tag 'drm-misc-next-2016-12-30' of git://anongit.freedesktop.org/git/drm-misc: (126 commits) drm: Add kerneldoc markup for new @scan parameters in drm_mm drm/mm: Document locking rules drm: Use drm_mm_insert_node_in_range_generic() for everyone drm: Apply range restriction after color adjustment when allocation drm: Wrap drm_mm_node.hole_follows drm: Apply tight eviction scanning to color_adjust drm: Simplify drm_mm scan-list manipulation drm: Optimise power-of-two alignments in drm_mm_scan_add_block() drm: Compute tight evictions for drm_mm_scan drm: Fix application of color vs range restriction when scanning drm_mm drm: Unconditionally do the range check in drm_mm_scan_add_block() drm: Rename prev_node to hole in drm_mm_scan_add_block() drm: Fix O= out-of-tree builds for selftests drm: Extract struct drm_mm_scan from struct drm_mm drm: Add asserts to catch overflow in drm_mm_init() and drm_mm_init_scan() drm: Simplify drm_mm_clean() drm: Detect overflow in drm_mm_reserve_node() drm: Fix kerneldoc for drm_mm_scan_remove_block() drm: Promote drm_mm alignment to u64 drm: kselftest for drm_mm and restricted color eviction ...
Diffstat (limited to 'lib')
-rw-r--r--lib/Kconfig7
-rw-r--r--lib/Makefile2
-rw-r--r--lib/prime_numbers.c314
3 files changed, 323 insertions, 0 deletions
diff --git a/lib/Kconfig b/lib/Kconfig
index 260a80e313b9..1788a1f50d28 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -550,4 +550,11 @@ config STACKDEPOT
config SBITMAP
bool
+config PRIME_NUMBERS
+ tristate "Prime number generator"
+ default n
+ help
+ Provides a helper module to generate prime numbers. Useful for writing
+ test code, especially when checking multiplication and divison.
+
endmenu
diff --git a/lib/Makefile b/lib/Makefile
index bc4073a8cd08..bdfc284c1d5a 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -196,6 +196,8 @@ obj-$(CONFIG_ASN1) += asn1_decoder.o
obj-$(CONFIG_FONT_SUPPORT) += fonts/
+obj-$(CONFIG_PRIME_NUMBERS) += prime_numbers.o
+
hostprogs-y := gen_crc32table
clean-files := crc32table.h
diff --git a/lib/prime_numbers.c b/lib/prime_numbers.c
new file mode 100644
index 000000000000..c9b3c29614aa
--- /dev/null
+++ b/lib/prime_numbers.c
@@ -0,0 +1,314 @@
+#define pr_fmt(fmt) "prime numbers: " fmt "\n"
+
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/prime_numbers.h>
+#include <linux/slab.h>
+
+#define bitmap_size(nbits) (BITS_TO_LONGS(nbits) * sizeof(unsigned long))
+
+struct primes {
+ struct rcu_head rcu;
+ unsigned long last, sz;
+ unsigned long primes[];
+};
+
+#if BITS_PER_LONG == 64
+static const struct primes small_primes = {
+ .last = 61,
+ .sz = 64,
+ .primes = {
+ BIT(2) |
+ BIT(3) |
+ BIT(5) |
+ BIT(7) |
+ BIT(11) |
+ BIT(13) |
+ BIT(17) |
+ BIT(19) |
+ BIT(23) |
+ BIT(29) |
+ BIT(31) |
+ BIT(37) |
+ BIT(41) |
+ BIT(43) |
+ BIT(47) |
+ BIT(53) |
+ BIT(59) |
+ BIT(61)
+ }
+};
+#elif BITS_PER_LONG == 32
+static const struct primes small_primes = {
+ .last = 31,
+ .sz = 32,
+ .primes = {
+ BIT(2) |
+ BIT(3) |
+ BIT(5) |
+ BIT(7) |
+ BIT(11) |
+ BIT(13) |
+ BIT(17) |
+ BIT(19) |
+ BIT(23) |
+ BIT(29) |
+ BIT(31)
+ }
+};
+#else
+#error "unhandled BITS_PER_LONG"
+#endif
+
+static DEFINE_MUTEX(lock);
+static const struct primes __rcu *primes = RCU_INITIALIZER(&small_primes);
+
+static unsigned long selftest_max;
+
+static bool slow_is_prime_number(unsigned long x)
+{
+ unsigned long y = int_sqrt(x);
+
+ while (y > 1) {
+ if ((x % y) == 0)
+ break;
+ y--;
+ }
+
+ return y == 1;
+}
+
+static unsigned long slow_next_prime_number(unsigned long x)
+{
+ while (x < ULONG_MAX && !slow_is_prime_number(++x))
+ ;
+
+ return x;
+}
+
+static unsigned long clear_multiples(unsigned long x,
+ unsigned long *p,
+ unsigned long start,
+ unsigned long end)
+{
+ unsigned long m;
+
+ m = 2 * x;
+ if (m < start)
+ m = roundup(start, x);
+
+ while (m < end) {
+ __clear_bit(m, p);
+ m += x;
+ }
+
+ return x;
+}
+
+static bool expand_to_next_prime(unsigned long x)
+{
+ const struct primes *p;
+ struct primes *new;
+ unsigned long sz, y;
+
+ /* Betrand's Postulate (or Chebyshev's theorem) states that if n > 3,
+ * there is always at least one prime p between n and 2n - 2.
+ * Equivalently, if n > 1, then there is always at least one prime p
+ * such that n < p < 2n.
+ *
+ * http://mathworld.wolfram.com/BertrandsPostulate.html
+ * https://en.wikipedia.org/wiki/Bertrand's_postulate
+ */
+ sz = 2 * x;
+ if (sz < x)
+ return false;
+
+ sz = round_up(sz, BITS_PER_LONG);
+ new = kmalloc(sizeof(*new) + bitmap_size(sz), GFP_KERNEL);
+ if (!new)
+ return false;
+
+ mutex_lock(&lock);
+ p = rcu_dereference_protected(primes, lockdep_is_held(&lock));
+ if (x < p->last) {
+ kfree(new);
+ goto unlock;
+ }
+
+ /* Where memory permits, track the primes using the
+ * Sieve of Eratosthenes. The sieve is to remove all multiples of known
+ * primes from the set, what remains in the set is therefore prime.
+ */
+ bitmap_fill(new->primes, sz);
+ bitmap_copy(new->primes, p->primes, p->sz);
+ for (y = 2UL; y < sz; y = find_next_bit(new->primes, sz, y + 1))
+ new->last = clear_multiples(y, new->primes, p->sz, sz);
+ new->sz = sz;
+
+ BUG_ON(new->last <= x);
+
+ rcu_assign_pointer(primes, new);
+ if (p != &small_primes)
+ kfree_rcu((struct primes *)p, rcu);
+
+unlock:
+ mutex_unlock(&lock);
+ return true;
+}
+
+static void free_primes(void)
+{
+ const struct primes *p;
+
+ mutex_lock(&lock);
+ p = rcu_dereference_protected(primes, lockdep_is_held(&lock));
+ if (p != &small_primes) {
+ rcu_assign_pointer(primes, &small_primes);
+ kfree_rcu((struct primes *)p, rcu);
+ }
+ mutex_unlock(&lock);
+}
+
+/**
+ * next_prime_number - return the next prime number
+ * @x: the starting point for searching to test
+ *
+ * A prime number is an integer greater than 1 that is only divisible by
+ * itself and 1. The set of prime numbers is computed using the Sieve of
+ * Eratoshenes (on finding a prime, all multiples of that prime are removed
+ * from the set) enabling a fast lookup of the next prime number larger than
+ * @x. If the sieve fails (memory limitation), the search falls back to using
+ * slow trial-divison, up to the value of ULONG_MAX (which is reported as the
+ * final prime as a sentinel).
+ *
+ * Returns: the next prime number larger than @x
+ */
+unsigned long next_prime_number(unsigned long x)
+{
+ const struct primes *p;
+
+ rcu_read_lock();
+ p = rcu_dereference(primes);
+ while (x >= p->last) {
+ rcu_read_unlock();
+
+ if (!expand_to_next_prime(x))
+ return slow_next_prime_number(x);
+
+ rcu_read_lock();
+ p = rcu_dereference(primes);
+ }
+ x = find_next_bit(p->primes, p->last, x + 1);
+ rcu_read_unlock();
+
+ return x;
+}
+EXPORT_SYMBOL(next_prime_number);
+
+/**
+ * is_prime_number - test whether the given number is prime
+ * @x: the number to test
+ *
+ * A prime number is an integer greater than 1 that is only divisible by
+ * itself and 1. Internally a cache of prime numbers is kept (to speed up
+ * searching for sequential primes, see next_prime_number()), but if the number
+ * falls outside of that cache, its primality is tested using trial-divison.
+ *
+ * Returns: true if @x is prime, false for composite numbers.
+ */
+bool is_prime_number(unsigned long x)
+{
+ const struct primes *p;
+ bool result;
+
+ rcu_read_lock();
+ p = rcu_dereference(primes);
+ while (x >= p->sz) {
+ rcu_read_unlock();
+
+ if (!expand_to_next_prime(x))
+ return slow_is_prime_number(x);
+
+ rcu_read_lock();
+ p = rcu_dereference(primes);
+ }
+ result = test_bit(x, p->primes);
+ rcu_read_unlock();
+
+ return result;
+}
+EXPORT_SYMBOL(is_prime_number);
+
+static void dump_primes(void)
+{
+ const struct primes *p;
+ char *buf;
+
+ buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+
+ rcu_read_lock();
+ p = rcu_dereference(primes);
+
+ if (buf)
+ bitmap_print_to_pagebuf(true, buf, p->primes, p->sz);
+ pr_info("primes.{last=%lu, .sz=%lu, .primes[]=...x%lx} = %s",
+ p->last, p->sz, p->primes[BITS_TO_LONGS(p->sz) - 1], buf);
+
+ rcu_read_unlock();
+
+ kfree(buf);
+}
+
+static int selftest(unsigned long max)
+{
+ unsigned long x, last;
+
+ if (!max)
+ return 0;
+
+ for (last = 0, x = 2; x < max; x++) {
+ bool slow = slow_is_prime_number(x);
+ bool fast = is_prime_number(x);
+
+ if (slow != fast) {
+ pr_err("inconsistent result for is-prime(%lu): slow=%s, fast=%s!",
+ x, slow ? "yes" : "no", fast ? "yes" : "no");
+ goto err;
+ }
+
+ if (!slow)
+ continue;
+
+ if (next_prime_number(last) != x) {
+ pr_err("incorrect result for next-prime(%lu): expected %lu, got %lu",
+ last, x, next_prime_number(last));
+ goto err;
+ }
+ last = x;
+ }
+
+ pr_info("selftest(%lu) passed, last prime was %lu", x, last);
+ return 0;
+
+err:
+ dump_primes();
+ return -EINVAL;
+}
+
+static int __init primes_init(void)
+{
+ return selftest(selftest_max);
+}
+
+static void __exit primes_exit(void)
+{
+ free_primes();
+}
+
+module_init(primes_init);
+module_exit(primes_exit);
+
+module_param_named(selftest, selftest_max, ulong, 0400);
+
+MODULE_AUTHOR("Intel Corporation");
+MODULE_LICENSE("GPL");