tools lib: Adopt list_sort() from the kernel sources

/* SPDX-License-Identifier: GPL-2.0 */

#ifndef _LINUX_LIST_SORT_H

#define _LINUX_LIST_SORT_H

#include <linux/types.h>

struct list_head;

typedef int __attribute__((nonnull(2,3))) (*list_cmp_func_t)(void *,

		const struct list_head *, const struct list_head *);

__attribute__((nonnull(2,3)))

void list_sort(void *priv, struct list_head *head, list_cmp_func_t cmp);

#endif

// SPDX-License-Identifier: GPL-2.0

#include <linux/kernel.h>

#include <linux/compiler.h>

#include <linux/export.h>

#include <linux/string.h>

#include <linux/list_sort.h>

#include <linux/list.h>

/*

 * Returns a list organized in an intermediate format suited

 * to chaining of merge() calls: null-terminated, no reserved or

 * sentinel head node, "prev" links not maintained.

 */

__attribute__((nonnull(2,3,4)))

static struct list_head *merge(void *priv, list_cmp_func_t cmp,

				struct list_head *a, struct list_head *b)

{

	struct list_head *head, **tail = &head;

	for (;;) {

		/* if equal, take 'a' -- important for sort stability */

		if (cmp(priv, a, b) <= 0) {

			*tail = a;

			tail = &a->next;

			a = a->next;

			if (!a) {

				*tail = b;

				break;

			}

		} else {

			*tail = b;

			tail = &b->next;

			b = b->next;

			if (!b) {

				*tail = a;

				break;

			}

		}

	}

	return head;

}

/*

 * Combine final list merge with restoration of standard doubly-linked

 * list structure.  This approach duplicates code from merge(), but

 * runs faster than the tidier alternatives of either a separate final

 * prev-link restoration pass, or maintaining the prev links

 * throughout.

 */

__attribute__((nonnull(2,3,4,5)))

static void merge_final(void *priv, list_cmp_func_t cmp, struct list_head *head,

			struct list_head *a, struct list_head *b)

{

	struct list_head *tail = head;

	u8 count = 0;

	for (;;) {

		/* if equal, take 'a' -- important for sort stability */

		if (cmp(priv, a, b) <= 0) {

			tail->next = a;

			a->prev = tail;

			tail = a;

			a = a->next;

			if (!a)

				break;

		} else {

			tail->next = b;

			b->prev = tail;

			tail = b;

			b = b->next;

			if (!b) {

				b = a;

				break;

			}

		}

	}

	/* Finish linking remainder of list b on to tail */

	tail->next = b;

	do {

		/*

		 * If the merge is highly unbalanced (e.g. the input is

		 * already sorted), this loop may run many iterations.

		 * Continue callbacks to the client even though no

		 * element comparison is needed, so the client's cmp()

		 * routine can invoke cond_resched() periodically.

		 */

		if (unlikely(!++count))

			cmp(priv, b, b);

		b->prev = tail;

		tail = b;

		b = b->next;

	} while (b);

	/* And the final links to make a circular doubly-linked list */

	tail->next = head;

	head->prev = tail;

}

/**

 * list_sort - sort a list

 * @priv: private data, opaque to list_sort(), passed to @cmp

 * @head: the list to sort

 * @cmp: the elements comparison function

 *

 * The comparison function @cmp must return > 0 if @a should sort after

 * @b ("@a > @b" if you want an ascending sort), and <= 0 if @a should

 * sort before @b *or* their original order should be preserved.  It is

 * always called with the element that came first in the input in @a,

 * and list_sort is a stable sort, so it is not necessary to distinguish

 * the @a < @b and @a == @b cases.

 *

 * This is compatible with two styles of @cmp function:

 * - The traditional style which returns <0 / =0 / >0, or

 * - Returning a boolean 0/1.

 * The latter offers a chance to save a few cycles in the comparison

 * (which is used by e.g. plug_ctx_cmp() in block/blk-mq.c).

 *

 * A good way to write a multi-word comparison is::

 *

 *	if (a->high != b->high)

 *		return a->high > b->high;

 *	if (a->middle != b->middle)

 *		return a->middle > b->middle;

 *	return a->low > b->low;

 *

 *

 * This mergesort is as eager as possible while always performing at least

 * 2:1 balanced merges.  Given two pending sublists of size 2^k, they are

 * merged to a size-2^(k+1) list as soon as we have 2^k following elements.

 *

 * Thus, it will avoid cache thrashing as long as 3*2^k elements can

 * fit into the cache.  Not quite as good as a fully-eager bottom-up

 * mergesort, but it does use 0.2*n fewer comparisons, so is faster in

 * the common case that everything fits into L1.

 *

 *

 * The merging is controlled by "count", the number of elements in the

 * pending lists.  This is beautifully simple code, but rather subtle.

 *

 * Each time we increment "count", we set one bit (bit k) and clear

 * bits k-1 .. 0.  Each time this happens (except the very first time

 * for each bit, when count increments to 2^k), we merge two lists of

 * size 2^k into one list of size 2^(k+1).

 *

 * This merge happens exactly when the count reaches an odd multiple of

 * 2^k, which is when we have 2^k elements pending in smaller lists,

 * so it's safe to merge away two lists of size 2^k.

 *

 * After this happens twice, we have created two lists of size 2^(k+1),

 * which will be merged into a list of size 2^(k+2) before we create

 * a third list of size 2^(k+1), so there are never more than two pending.

 *

 * The number of pending lists of size 2^k is determined by the

 * state of bit k of "count" plus two extra pieces of information:

 *

 * - The state of bit k-1 (when k == 0, consider bit -1 always set), and

 * - Whether the higher-order bits are zero or non-zero (i.e.

 *   is count >= 2^(k+1)).

 *

 * There are six states we distinguish.  "x" represents some arbitrary

 * bits, and "y" represents some arbitrary non-zero bits:

 * 0:  00x: 0 pending of size 2^k;           x pending of sizes < 2^k

 * 1:  01x: 0 pending of size 2^k; 2^(k-1) + x pending of sizes < 2^k

 * 2: x10x: 0 pending of size 2^k; 2^k     + x pending of sizes < 2^k

 * 3: x11x: 1 pending of size 2^k; 2^(k-1) + x pending of sizes < 2^k

 * 4: y00x: 1 pending of size 2^k; 2^k     + x pending of sizes < 2^k

 * 5: y01x: 2 pending of size 2^k; 2^(k-1) + x pending of sizes < 2^k

 * (merge and loop back to state 2)

 *

 * We gain lists of size 2^k in the 2->3 and 4->5 transitions (because

 * bit k-1 is set while the more significant bits are non-zero) and

 * merge them away in the 5->2 transition.  Note in particular that just

 * before the 5->2 transition, all lower-order bits are 11 (state 3),

 * so there is one list of each smaller size.

 *

 * When we reach the end of the input, we merge all the pending

 * lists, from smallest to largest.  If you work through cases 2 to

 * 5 above, you can see that the number of elements we merge with a list

 * of size 2^k varies from 2^(k-1) (cases 3 and 5 when x == 0) to

 * 2^(k+1) - 1 (second merge of case 5 when x == 2^(k-1) - 1).

 */

__attribute__((nonnull(2,3)))

void list_sort(void *priv, struct list_head *head, list_cmp_func_t cmp)

{

	struct list_head *list = head->next, *pending = NULL;

	size_t count = 0;	/* Count of pending */

	if (list == head->prev)	/* Zero or one elements */

		return;

	/* Convert to a null-terminated singly-linked list. */

	head->prev->next = NULL;

	/*

	 * Data structure invariants:

	 * - All lists are singly linked and null-terminated; prev

	 *   pointers are not maintained.

	 * - pending is a prev-linked "list of lists" of sorted

	 *   sublists awaiting further merging.

	 * - Each of the sorted sublists is power-of-two in size.

	 * - Sublists are sorted by size and age, smallest & newest at front.

	 * - There are zero to two sublists of each size.

	 * - A pair of pending sublists are merged as soon as the number

	 *   of following pending elements equals their size (i.e.

	 *   each time count reaches an odd multiple of that size).

	 *   That ensures each later final merge will be at worst 2:1.

	 * - Each round consists of:

	 *   - Merging the two sublists selected by the highest bit

	 *     which flips when count is incremented, and

	 *   - Adding an element from the input as a size-1 sublist.

	 */

	do {

		size_t bits;

		struct list_head **tail = &pending;

		/* Find the least-significant clear bit in count */

		for (bits = count; bits & 1; bits >>= 1)

			tail = &(*tail)->prev;

		/* Do the indicated merge */

		if (likely(bits)) {

			struct list_head *a = *tail, *b = a->prev;

			a = merge(priv, cmp, b, a);

			/* Install the merged result in place of the inputs */

			a->prev = b->prev;

			*tail = a;

		}

		/* Move one element from input list to pending */

		list->prev = pending;

		pending = list;

		list = list->next;

		pending->next = NULL;

		count++;

	} while (list);

	/* End of input; merge together all the pending lists. */

	list = pending;

	pending = pending->prev;

	for (;;) {

		struct list_head *next = pending->prev;

		if (!next)

			break;

		list = merge(priv, cmp, pending, list);

		pending = next;

	}

	/* The final merge, rebuilding prev links */

	merge_final(priv, cmp, head, pending, list);

}

EXPORT_SYMBOL(list_sort);

tools/lib/symbol/kallsyms.h

tools/lib/find_bit.c

tools/lib/bitmap.c

tools/lib/list_sort.c

tools/lib/str_error_r.c

tools/lib/vsprintf.c

tools/lib/zalloc.c

include/linux/const.h

include/vdso/const.h

include/linux/hash.h

include/linux/list-sort.h

include/uapi/linux/hw_breakpoint.h

arch/x86/include/asm/disabled-features.h

arch/x86/include/asm/required-features.h

check include/linux/build_bug.h       '-I "^#\(ifndef\|endif\)\( \/\/\)* static_assert$"'

check include/linux/ctype.h	      '-I "isdigit("'

check lib/ctype.c		      '-I "^EXPORT_SYMBOL" -I "^#include <linux/export.h>" -B'

check lib/list_sort.c		      '-I "^#include <linux/bug.h>"'

# diff non-symmetric files

check_2 tools/perf/arch/x86/entry/syscalls/syscall_64.tbl arch/x86/entry/syscalls/syscall_64.tbl

perf-y += branch.o

perf-y += mem2node.o

perf-y += clockid.o

perf-y += list_sort.o

perf-$(CONFIG_LIBBPF) += bpf-loader.o

perf-$(CONFIG_LIBBPF) += bpf_map.o

$(OUTPUT)util/vsprintf.o: ../lib/vsprintf.c FORCE

	$(call rule_mkdir)

	$(call if_changed_dep,cc_o_c)

$(OUTPUT)util/list_sort.o: ../lib/list_sort.c FORCE

	$(call rule_mkdir)

	$(call if_changed_dep,cc_o_c)