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([2602:47:d48c:8101:3efa:624c:5fb:32c0]) by smtp.gmail.com with ESMTPSA id a8-20020a17090a688800b002135e8074b1sm390645pjd.55.2022.12.20.21.03.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Dec 2022 21:03:16 -0800 (PST) From: Richard Henderson To: qemu-devel@nongnu.org Cc: peter.maydell@linaro.org, =?utf-8?q?Alex_Benn=C3=A9e?= Subject: [PULL v2 01/14] util: Add interval-tree.c Date: Tue, 20 Dec 2022 21:03:00 -0800 Message-Id: <20221221050313.2950701-2-richard.henderson@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20221221050313.2950701-1-richard.henderson@linaro.org> References: <20221221050313.2950701-1-richard.henderson@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2607:f8b0:4864:20::102a; envelope-from=richard.henderson@linaro.org; helo=mail-pj1-x102a.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+patch=linaro.org@nongnu.org Sender: qemu-devel-bounces+patch=linaro.org@nongnu.org Copy and simplify the Linux kernel's interval_tree_generic.h, instantiating for uint64_t. Reviewed-by: Alex Bennée Signed-off-by: Richard Henderson --- include/qemu/interval-tree.h | 99 ++++ tests/unit/test-interval-tree.c | 209 ++++++++ util/interval-tree.c | 882 ++++++++++++++++++++++++++++++++ tests/unit/meson.build | 1 + util/meson.build | 1 + 5 files changed, 1192 insertions(+) create mode 100644 include/qemu/interval-tree.h create mode 100644 tests/unit/test-interval-tree.c create mode 100644 util/interval-tree.c diff --git a/include/qemu/interval-tree.h b/include/qemu/interval-tree.h new file mode 100644 index 0000000000..25006debe8 --- /dev/null +++ b/include/qemu/interval-tree.h @@ -0,0 +1,99 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* + * Interval trees. + * + * Derived from include/linux/interval_tree.h and its dependencies. + */ + +#ifndef QEMU_INTERVAL_TREE_H +#define QEMU_INTERVAL_TREE_H + +/* + * For now, don't expose Linux Red-Black Trees separately, but retain the + * separate type definitions to keep the implementation sane, and allow + * the possibility of disentangling them later. + */ +typedef struct RBNode +{ + /* Encodes parent with color in the lsb. */ + uintptr_t rb_parent_color; + struct RBNode *rb_right; + struct RBNode *rb_left; +} RBNode; + +typedef struct RBRoot +{ + RBNode *rb_node; +} RBRoot; + +typedef struct RBRootLeftCached { + RBRoot rb_root; + RBNode *rb_leftmost; +} RBRootLeftCached; + +typedef struct IntervalTreeNode +{ + RBNode rb; + + uint64_t start; /* Start of interval */ + uint64_t last; /* Last location _in_ interval */ + uint64_t subtree_last; +} IntervalTreeNode; + +typedef RBRootLeftCached IntervalTreeRoot; + +/** + * interval_tree_is_empty + * @root: root of the tree. + * + * Returns true if the tree contains no nodes. + */ +static inline bool interval_tree_is_empty(const IntervalTreeRoot *root) +{ + return root->rb_root.rb_node == NULL; +} + +/** + * interval_tree_insert + * @node: node to insert, + * @root: root of the tree. + * + * Insert @node into @root, and rebalance. + */ +void interval_tree_insert(IntervalTreeNode *node, IntervalTreeRoot *root); + +/** + * interval_tree_remove + * @node: node to remove, + * @root: root of the tree. + * + * Remove @node from @root, and rebalance. + */ +void interval_tree_remove(IntervalTreeNode *node, IntervalTreeRoot *root); + +/** + * interval_tree_iter_first: + * @root: root of the tree, + * @start, @last: the inclusive interval [start, last]. + * + * Locate the "first" of a set of nodes within the tree at @root + * that overlap the interval, where "first" is sorted by start. + * Returns NULL if no overlap found. + */ +IntervalTreeNode *interval_tree_iter_first(IntervalTreeRoot *root, + uint64_t start, uint64_t last); + +/** + * interval_tree_iter_next: + * @node: previous search result + * @start, @last: the inclusive interval [start, last]. + * + * Locate the "next" of a set of nodes within the tree that overlap the + * interval; @next is the result of a previous call to + * interval_tree_iter_{first,next}. Returns NULL if @next was the last + * node in the set. + */ +IntervalTreeNode *interval_tree_iter_next(IntervalTreeNode *node, + uint64_t start, uint64_t last); + +#endif /* QEMU_INTERVAL_TREE_H */ diff --git a/tests/unit/test-interval-tree.c b/tests/unit/test-interval-tree.c new file mode 100644 index 0000000000..119817a019 --- /dev/null +++ b/tests/unit/test-interval-tree.c @@ -0,0 +1,209 @@ +/* + * Test interval trees + * + * This work is licensed under the terms of the GNU LGPL, version 2 or later. + * See the COPYING.LIB file in the top-level directory. + * + */ + +#include "qemu/osdep.h" +#include "qemu/interval-tree.h" + +static IntervalTreeNode nodes[20]; +static IntervalTreeRoot root; + +static void rand_interval(IntervalTreeNode *n, uint64_t start, uint64_t last) +{ + gint32 s_ofs, l_ofs, l_max; + + if (last - start > INT32_MAX) { + l_max = INT32_MAX; + } else { + l_max = last - start; + } + s_ofs = g_test_rand_int_range(0, l_max); + l_ofs = g_test_rand_int_range(s_ofs, l_max); + + n->start = start + s_ofs; + n->last = start + l_ofs; +} + +static void test_empty(void) +{ + g_assert(root.rb_root.rb_node == NULL); + g_assert(root.rb_leftmost == NULL); + g_assert(interval_tree_iter_first(&root, 0, UINT64_MAX) == NULL); +} + +static void test_find_one_point(void) +{ + /* Create a tree of a single node, which is the point [1,1]. */ + nodes[0].start = 1; + nodes[0].last = 1; + + interval_tree_insert(&nodes[0], &root); + + g_assert(interval_tree_iter_first(&root, 0, 9) == &nodes[0]); + g_assert(interval_tree_iter_next(&nodes[0], 0, 9) == NULL); + g_assert(interval_tree_iter_first(&root, 0, 0) == NULL); + g_assert(interval_tree_iter_next(&nodes[0], 0, 0) == NULL); + g_assert(interval_tree_iter_first(&root, 0, 1) == &nodes[0]); + g_assert(interval_tree_iter_first(&root, 1, 1) == &nodes[0]); + g_assert(interval_tree_iter_first(&root, 1, 2) == &nodes[0]); + g_assert(interval_tree_iter_first(&root, 2, 2) == NULL); + + interval_tree_remove(&nodes[0], &root); + g_assert(root.rb_root.rb_node == NULL); + g_assert(root.rb_leftmost == NULL); +} + +static void test_find_two_point(void) +{ + IntervalTreeNode *find0, *find1; + + /* Create a tree of a two nodes, which are both the point [1,1]. */ + nodes[0].start = 1; + nodes[0].last = 1; + nodes[1] = nodes[0]; + + interval_tree_insert(&nodes[0], &root); + interval_tree_insert(&nodes[1], &root); + + find0 = interval_tree_iter_first(&root, 0, 9); + g_assert(find0 == &nodes[0] || find0 == &nodes[1]); + + find1 = interval_tree_iter_next(find0, 0, 9); + g_assert(find1 == &nodes[0] || find1 == &nodes[1]); + g_assert(find0 != find1); + + interval_tree_remove(&nodes[1], &root); + + g_assert(interval_tree_iter_first(&root, 0, 9) == &nodes[0]); + g_assert(interval_tree_iter_next(&nodes[0], 0, 9) == NULL); + + interval_tree_remove(&nodes[0], &root); +} + +static void test_find_one_range(void) +{ + /* Create a tree of a single node, which is the range [1,8]. */ + nodes[0].start = 1; + nodes[0].last = 8; + + interval_tree_insert(&nodes[0], &root); + + g_assert(interval_tree_iter_first(&root, 0, 9) == &nodes[0]); + g_assert(interval_tree_iter_next(&nodes[0], 0, 9) == NULL); + g_assert(interval_tree_iter_first(&root, 0, 0) == NULL); + g_assert(interval_tree_iter_first(&root, 0, 1) == &nodes[0]); + g_assert(interval_tree_iter_first(&root, 1, 1) == &nodes[0]); + g_assert(interval_tree_iter_first(&root, 4, 6) == &nodes[0]); + g_assert(interval_tree_iter_first(&root, 8, 8) == &nodes[0]); + g_assert(interval_tree_iter_first(&root, 9, 9) == NULL); + + interval_tree_remove(&nodes[0], &root); +} + +static void test_find_one_range_many(void) +{ + int i; + + /* + * Create a tree of many nodes in [0,99] and [200,299], + * but only one node with exactly [110,190]. + */ + nodes[0].start = 110; + nodes[0].last = 190; + + for (i = 1; i < ARRAY_SIZE(nodes) / 2; ++i) { + rand_interval(&nodes[i], 0, 99); + } + for (; i < ARRAY_SIZE(nodes); ++i) { + rand_interval(&nodes[i], 200, 299); + } + + for (i = 0; i < ARRAY_SIZE(nodes); ++i) { + interval_tree_insert(&nodes[i], &root); + } + + /* Test that we find exactly the one node. */ + g_assert(interval_tree_iter_first(&root, 100, 199) == &nodes[0]); + g_assert(interval_tree_iter_next(&nodes[0], 100, 199) == NULL); + g_assert(interval_tree_iter_first(&root, 100, 109) == NULL); + g_assert(interval_tree_iter_first(&root, 100, 110) == &nodes[0]); + g_assert(interval_tree_iter_first(&root, 111, 120) == &nodes[0]); + g_assert(interval_tree_iter_first(&root, 111, 199) == &nodes[0]); + g_assert(interval_tree_iter_first(&root, 190, 199) == &nodes[0]); + g_assert(interval_tree_iter_first(&root, 192, 199) == NULL); + + /* + * Test that if there are multiple matches, we return the one + * with the minimal start. + */ + g_assert(interval_tree_iter_first(&root, 100, 300) == &nodes[0]); + + /* Test that we don't find it after it is removed. */ + interval_tree_remove(&nodes[0], &root); + g_assert(interval_tree_iter_first(&root, 100, 199) == NULL); + + for (i = 1; i < ARRAY_SIZE(nodes); ++i) { + interval_tree_remove(&nodes[i], &root); + } +} + +static void test_find_many_range(void) +{ + IntervalTreeNode *find; + int i, n; + + n = g_test_rand_int_range(ARRAY_SIZE(nodes) / 3, ARRAY_SIZE(nodes) / 2); + + /* + * Create a fair few nodes in [2000,2999], with the others + * distributed around. + */ + for (i = 0; i < n; ++i) { + rand_interval(&nodes[i], 2000, 2999); + } + for (; i < ARRAY_SIZE(nodes) * 2 / 3; ++i) { + rand_interval(&nodes[i], 1000, 1899); + } + for (; i < ARRAY_SIZE(nodes); ++i) { + rand_interval(&nodes[i], 3100, 3999); + } + + for (i = 0; i < ARRAY_SIZE(nodes); ++i) { + interval_tree_insert(&nodes[i], &root); + } + + /* Test that we find all of the nodes. */ + find = interval_tree_iter_first(&root, 2000, 2999); + for (i = 0; find != NULL; i++) { + find = interval_tree_iter_next(find, 2000, 2999); + } + g_assert_cmpint(i, ==, n); + + g_assert(interval_tree_iter_first(&root, 0, 999) == NULL); + g_assert(interval_tree_iter_first(&root, 1900, 1999) == NULL); + g_assert(interval_tree_iter_first(&root, 3000, 3099) == NULL); + g_assert(interval_tree_iter_first(&root, 4000, UINT64_MAX) == NULL); + + for (i = 0; i < ARRAY_SIZE(nodes); ++i) { + interval_tree_remove(&nodes[i], &root); + } +} + +int main(int argc, char **argv) +{ + g_test_init(&argc, &argv, NULL); + + g_test_add_func("/interval-tree/empty", test_empty); + g_test_add_func("/interval-tree/find-one-point", test_find_one_point); + g_test_add_func("/interval-tree/find-two-point", test_find_two_point); + g_test_add_func("/interval-tree/find-one-range", test_find_one_range); + g_test_add_func("/interval-tree/find-one-range-many", + test_find_one_range_many); + g_test_add_func("/interval-tree/find-many-range", test_find_many_range); + + return g_test_run(); +} diff --git a/util/interval-tree.c b/util/interval-tree.c new file mode 100644 index 0000000000..4c0baf108f --- /dev/null +++ b/util/interval-tree.c @@ -0,0 +1,882 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ + +#include "qemu/osdep.h" +#include "qemu/interval-tree.h" +#include "qemu/atomic.h" + +/* + * Red Black Trees. + * + * For now, don't expose Linux Red-Black Trees separately, but retain the + * separate type definitions to keep the implementation sane, and allow + * the possibility of separating them later. + * + * Derived from include/linux/rbtree_augmented.h and its dependencies. + */ + +/* + * red-black trees properties: https://en.wikipedia.org/wiki/Rbtree + * + * 1) A node is either red or black + * 2) The root is black + * 3) All leaves (NULL) are black + * 4) Both children of every red node are black + * 5) Every simple path from root to leaves contains the same number + * of black nodes. + * + * 4 and 5 give the O(log n) guarantee, since 4 implies you cannot have two + * consecutive red nodes in a path and every red node is therefore followed by + * a black. So if B is the number of black nodes on every simple path (as per + * 5), then the longest possible path due to 4 is 2B. + * + * We shall indicate color with case, where black nodes are uppercase and red + * nodes will be lowercase. Unknown color nodes shall be drawn as red within + * parentheses and have some accompanying text comment. + * + * Notes on lockless lookups: + * + * All stores to the tree structure (rb_left and rb_right) must be done using + * WRITE_ONCE [qatomic_set for QEMU]. And we must not inadvertently cause + * (temporary) loops in the tree structure as seen in program order. + * + * These two requirements will allow lockless iteration of the tree -- not + * correct iteration mind you, tree rotations are not atomic so a lookup might + * miss entire subtrees. + * + * But they do guarantee that any such traversal will only see valid elements + * and that it will indeed complete -- does not get stuck in a loop. + * + * It also guarantees that if the lookup returns an element it is the 'correct' + * one. But not returning an element does _NOT_ mean it's not present. + * + * NOTE: + * + * Stores to __rb_parent_color are not important for simple lookups so those + * are left undone as of now. Nor did I check for loops involving parent + * pointers. + */ + +typedef enum RBColor +{ + RB_RED, + RB_BLACK, +} RBColor; + +typedef struct RBAugmentCallbacks { + void (*propagate)(RBNode *node, RBNode *stop); + void (*copy)(RBNode *old, RBNode *new); + void (*rotate)(RBNode *old, RBNode *new); +} RBAugmentCallbacks; + +static inline RBNode *rb_parent(const RBNode *n) +{ + return (RBNode *)(n->rb_parent_color & ~1); +} + +static inline RBNode *rb_red_parent(const RBNode *n) +{ + return (RBNode *)n->rb_parent_color; +} + +static inline RBColor pc_color(uintptr_t pc) +{ + return (RBColor)(pc & 1); +} + +static inline bool pc_is_red(uintptr_t pc) +{ + return pc_color(pc) == RB_RED; +} + +static inline bool pc_is_black(uintptr_t pc) +{ + return !pc_is_red(pc); +} + +static inline RBColor rb_color(const RBNode *n) +{ + return pc_color(n->rb_parent_color); +} + +static inline bool rb_is_red(const RBNode *n) +{ + return pc_is_red(n->rb_parent_color); +} + +static inline bool rb_is_black(const RBNode *n) +{ + return pc_is_black(n->rb_parent_color); +} + +static inline void rb_set_black(RBNode *n) +{ + n->rb_parent_color |= RB_BLACK; +} + +static inline void rb_set_parent_color(RBNode *n, RBNode *p, RBColor color) +{ + n->rb_parent_color = (uintptr_t)p | color; +} + +static inline void rb_set_parent(RBNode *n, RBNode *p) +{ + rb_set_parent_color(n, p, rb_color(n)); +} + +static inline void rb_link_node(RBNode *node, RBNode *parent, RBNode **rb_link) +{ + node->rb_parent_color = (uintptr_t)parent; + node->rb_left = node->rb_right = NULL; + + qatomic_set(rb_link, node); +} + +static RBNode *rb_next(RBNode *node) +{ + RBNode *parent; + + /* OMIT: if empty node, return null. */ + + /* + * If we have a right-hand child, go down and then left as far as we can. + */ + if (node->rb_right) { + node = node->rb_right; + while (node->rb_left) { + node = node->rb_left; + } + return node; + } + + /* + * No right-hand children. Everything down and left is smaller than us, + * so any 'next' node must be in the general direction of our parent. + * Go up the tree; any time the ancestor is a right-hand child of its + * parent, keep going up. First time it's a left-hand child of its + * parent, said parent is our 'next' node. + */ + while ((parent = rb_parent(node)) && node == parent->rb_right) { + node = parent; + } + + return parent; +} + +static inline void rb_change_child(RBNode *old, RBNode *new, + RBNode *parent, RBRoot *root) +{ + if (!parent) { + qatomic_set(&root->rb_node, new); + } else if (parent->rb_left == old) { + qatomic_set(&parent->rb_left, new); + } else { + qatomic_set(&parent->rb_right, new); + } +} + +static inline void rb_rotate_set_parents(RBNode *old, RBNode *new, + RBRoot *root, RBColor color) +{ + RBNode *parent = rb_parent(old); + + new->rb_parent_color = old->rb_parent_color; + rb_set_parent_color(old, new, color); + rb_change_child(old, new, parent, root); +} + +static void rb_insert_augmented(RBNode *node, RBRoot *root, + const RBAugmentCallbacks *augment) +{ + RBNode *parent = rb_red_parent(node), *gparent, *tmp; + + while (true) { + /* + * Loop invariant: node is red. + */ + if (unlikely(!parent)) { + /* + * The inserted node is root. Either this is the first node, or + * we recursed at Case 1 below and are no longer violating 4). + */ + rb_set_parent_color(node, NULL, RB_BLACK); + break; + } + + /* + * If there is a black parent, we are done. Otherwise, take some + * corrective action as, per 4), we don't want a red root or two + * consecutive red nodes. + */ + if (rb_is_black(parent)) { + break; + } + + gparent = rb_red_parent(parent); + + tmp = gparent->rb_right; + if (parent != tmp) { /* parent == gparent->rb_left */ + if (tmp && rb_is_red(tmp)) { + /* + * Case 1 - node's uncle is red (color flips). + * + * G g + * / \ / \ + * p u --> P U + * / / + * n n + * + * However, since g's parent might be red, and 4) does not + * allow this, we need to recurse at g. + */ + rb_set_parent_color(tmp, gparent, RB_BLACK); + rb_set_parent_color(parent, gparent, RB_BLACK); + node = gparent; + parent = rb_parent(node); + rb_set_parent_color(node, parent, RB_RED); + continue; + } + + tmp = parent->rb_right; + if (node == tmp) { + /* + * Case 2 - node's uncle is black and node is + * the parent's right child (left rotate at parent). + * + * G G + * / \ / \ + * p U --> n U + * \ / + * n p + * + * This still leaves us in violation of 4), the + * continuation into Case 3 will fix that. + */ + tmp = node->rb_left; + qatomic_set(&parent->rb_right, tmp); + qatomic_set(&node->rb_left, parent); + if (tmp) { + rb_set_parent_color(tmp, parent, RB_BLACK); + } + rb_set_parent_color(parent, node, RB_RED); + augment->rotate(parent, node); + parent = node; + tmp = node->rb_right; + } + + /* + * Case 3 - node's uncle is black and node is + * the parent's left child (right rotate at gparent). + * + * G P + * / \ / \ + * p U --> n g + * / \ + * n U + */ + qatomic_set(&gparent->rb_left, tmp); /* == parent->rb_right */ + qatomic_set(&parent->rb_right, gparent); + if (tmp) { + rb_set_parent_color(tmp, gparent, RB_BLACK); + } + rb_rotate_set_parents(gparent, parent, root, RB_RED); + augment->rotate(gparent, parent); + break; + } else { + tmp = gparent->rb_left; + if (tmp && rb_is_red(tmp)) { + /* Case 1 - color flips */ + rb_set_parent_color(tmp, gparent, RB_BLACK); + rb_set_parent_color(parent, gparent, RB_BLACK); + node = gparent; + parent = rb_parent(node); + rb_set_parent_color(node, parent, RB_RED); + continue; + } + + tmp = parent->rb_left; + if (node == tmp) { + /* Case 2 - right rotate at parent */ + tmp = node->rb_right; + qatomic_set(&parent->rb_left, tmp); + qatomic_set(&node->rb_right, parent); + if (tmp) { + rb_set_parent_color(tmp, parent, RB_BLACK); + } + rb_set_parent_color(parent, node, RB_RED); + augment->rotate(parent, node); + parent = node; + tmp = node->rb_left; + } + + /* Case 3 - left rotate at gparent */ + qatomic_set(&gparent->rb_right, tmp); /* == parent->rb_left */ + qatomic_set(&parent->rb_left, gparent); + if (tmp) { + rb_set_parent_color(tmp, gparent, RB_BLACK); + } + rb_rotate_set_parents(gparent, parent, root, RB_RED); + augment->rotate(gparent, parent); + break; + } + } +} + +static void rb_insert_augmented_cached(RBNode *node, + RBRootLeftCached *root, bool newleft, + const RBAugmentCallbacks *augment) +{ + if (newleft) { + root->rb_leftmost = node; + } + rb_insert_augmented(node, &root->rb_root, augment); +} + +static void rb_erase_color(RBNode *parent, RBRoot *root, + const RBAugmentCallbacks *augment) +{ + RBNode *node = NULL, *sibling, *tmp1, *tmp2; + + while (true) { + /* + * Loop invariants: + * - node is black (or NULL on first iteration) + * - node is not the root (parent is not NULL) + * - All leaf paths going through parent and node have a + * black node count that is 1 lower than other leaf paths. + */ + sibling = parent->rb_right; + if (node != sibling) { /* node == parent->rb_left */ + if (rb_is_red(sibling)) { + /* + * Case 1 - left rotate at parent + * + * P S + * / \ / \ + * N s --> p Sr + * / \ / \ + * Sl Sr N Sl + */ + tmp1 = sibling->rb_left; + qatomic_set(&parent->rb_right, tmp1); + qatomic_set(&sibling->rb_left, parent); + rb_set_parent_color(tmp1, parent, RB_BLACK); + rb_rotate_set_parents(parent, sibling, root, RB_RED); + augment->rotate(parent, sibling); + sibling = tmp1; + } + tmp1 = sibling->rb_right; + if (!tmp1 || rb_is_black(tmp1)) { + tmp2 = sibling->rb_left; + if (!tmp2 || rb_is_black(tmp2)) { + /* + * Case 2 - sibling color flip + * (p could be either color here) + * + * (p) (p) + * / \ / \ + * N S --> N s + * / \ / \ + * Sl Sr Sl Sr + * + * This leaves us violating 5) which + * can be fixed by flipping p to black + * if it was red, or by recursing at p. + * p is red when coming from Case 1. + */ + rb_set_parent_color(sibling, parent, RB_RED); + if (rb_is_red(parent)) { + rb_set_black(parent); + } else { + node = parent; + parent = rb_parent(node); + if (parent) { + continue; + } + } + break; + } + /* + * Case 3 - right rotate at sibling + * (p could be either color here) + * + * (p) (p) + * / \ / \ + * N S --> N sl + * / \ \ + * sl Sr S + * \ + * Sr + * + * Note: p might be red, and then bot + * p and sl are red after rotation (which + * breaks property 4). This is fixed in + * Case 4 (in rb_rotate_set_parents() + * which set sl the color of p + * and set p RB_BLACK) + * + * (p) (sl) + * / \ / \ + * N sl --> P S + * \ / \ + * S N Sr + * \ + * Sr + */ + tmp1 = tmp2->rb_right; + qatomic_set(&sibling->rb_left, tmp1); + qatomic_set(&tmp2->rb_right, sibling); + qatomic_set(&parent->rb_right, tmp2); + if (tmp1) { + rb_set_parent_color(tmp1, sibling, RB_BLACK); + } + augment->rotate(sibling, tmp2); + tmp1 = sibling; + sibling = tmp2; + } + /* + * Case 4 - left rotate at parent + color flips + * (p and sl could be either color here. + * After rotation, p becomes black, s acquires + * p's color, and sl keeps its color) + * + * (p) (s) + * / \ / \ + * N S --> P Sr + * / \ / \ + * (sl) sr N (sl) + */ + tmp2 = sibling->rb_left; + qatomic_set(&parent->rb_right, tmp2); + qatomic_set(&sibling->rb_left, parent); + rb_set_parent_color(tmp1, sibling, RB_BLACK); + if (tmp2) { + rb_set_parent(tmp2, parent); + } + rb_rotate_set_parents(parent, sibling, root, RB_BLACK); + augment->rotate(parent, sibling); + break; + } else { + sibling = parent->rb_left; + if (rb_is_red(sibling)) { + /* Case 1 - right rotate at parent */ + tmp1 = sibling->rb_right; + qatomic_set(&parent->rb_left, tmp1); + qatomic_set(&sibling->rb_right, parent); + rb_set_parent_color(tmp1, parent, RB_BLACK); + rb_rotate_set_parents(parent, sibling, root, RB_RED); + augment->rotate(parent, sibling); + sibling = tmp1; + } + tmp1 = sibling->rb_left; + if (!tmp1 || rb_is_black(tmp1)) { + tmp2 = sibling->rb_right; + if (!tmp2 || rb_is_black(tmp2)) { + /* Case 2 - sibling color flip */ + rb_set_parent_color(sibling, parent, RB_RED); + if (rb_is_red(parent)) { + rb_set_black(parent); + } else { + node = parent; + parent = rb_parent(node); + if (parent) { + continue; + } + } + break; + } + /* Case 3 - left rotate at sibling */ + tmp1 = tmp2->rb_left; + qatomic_set(&sibling->rb_right, tmp1); + qatomic_set(&tmp2->rb_left, sibling); + qatomic_set(&parent->rb_left, tmp2); + if (tmp1) { + rb_set_parent_color(tmp1, sibling, RB_BLACK); + } + augment->rotate(sibling, tmp2); + tmp1 = sibling; + sibling = tmp2; + } + /* Case 4 - right rotate at parent + color flips */ + tmp2 = sibling->rb_right; + qatomic_set(&parent->rb_left, tmp2); + qatomic_set(&sibling->rb_right, parent); + rb_set_parent_color(tmp1, sibling, RB_BLACK); + if (tmp2) { + rb_set_parent(tmp2, parent); + } + rb_rotate_set_parents(parent, sibling, root, RB_BLACK); + augment->rotate(parent, sibling); + break; + } + } +} + +static void rb_erase_augmented(RBNode *node, RBRoot *root, + const RBAugmentCallbacks *augment) +{ + RBNode *child = node->rb_right; + RBNode *tmp = node->rb_left; + RBNode *parent, *rebalance; + uintptr_t pc; + + if (!tmp) { + /* + * Case 1: node to erase has no more than 1 child (easy!) + * + * Note that if there is one child it must be red due to 5) + * and node must be black due to 4). We adjust colors locally + * so as to bypass rb_erase_color() later on. + */ + pc = node->rb_parent_color; + parent = rb_parent(node); + rb_change_child(node, child, parent, root); + if (child) { + child->rb_parent_color = pc; + rebalance = NULL; + } else { + rebalance = pc_is_black(pc) ? parent : NULL; + } + tmp = parent; + } else if (!child) { + /* Still case 1, but this time the child is node->rb_left */ + pc = node->rb_parent_color; + parent = rb_parent(node); + tmp->rb_parent_color = pc; + rb_change_child(node, tmp, parent, root); + rebalance = NULL; + tmp = parent; + } else { + RBNode *successor = child, *child2; + tmp = child->rb_left; + if (!tmp) { + /* + * Case 2: node's successor is its right child + * + * (n) (s) + * / \ / \ + * (x) (s) -> (x) (c) + * \ + * (c) + */ + parent = successor; + child2 = successor->rb_right; + + augment->copy(node, successor); + } else { + /* + * Case 3: node's successor is leftmost under + * node's right child subtree + * + * (n) (s) + * / \ / \ + * (x) (y) -> (x) (y) + * / / + * (p) (p) + * / / + * (s) (c) + * \ + * (c) + */ + do { + parent = successor; + successor = tmp; + tmp = tmp->rb_left; + } while (tmp); + child2 = successor->rb_right; + qatomic_set(&parent->rb_left, child2); + qatomic_set(&successor->rb_right, child); + rb_set_parent(child, successor); + + augment->copy(node, successor); + augment->propagate(parent, successor); + } + + tmp = node->rb_left; + qatomic_set(&successor->rb_left, tmp); + rb_set_parent(tmp, successor); + + pc = node->rb_parent_color; + tmp = rb_parent(node); + rb_change_child(node, successor, tmp, root); + + if (child2) { + rb_set_parent_color(child2, parent, RB_BLACK); + rebalance = NULL; + } else { + rebalance = rb_is_black(successor) ? parent : NULL; + } + successor->rb_parent_color = pc; + tmp = successor; + } + + augment->propagate(tmp, NULL); + + if (rebalance) { + rb_erase_color(rebalance, root, augment); + } +} + +static void rb_erase_augmented_cached(RBNode *node, RBRootLeftCached *root, + const RBAugmentCallbacks *augment) +{ + if (root->rb_leftmost == node) { + root->rb_leftmost = rb_next(node); + } + rb_erase_augmented(node, &root->rb_root, augment); +} + + +/* + * Interval trees. + * + * Derived from lib/interval_tree.c and its dependencies, + * especially include/linux/interval_tree_generic.h. + */ + +#define rb_to_itree(N) container_of(N, IntervalTreeNode, rb) + +static bool interval_tree_compute_max(IntervalTreeNode *node, bool exit) +{ + IntervalTreeNode *child; + uint64_t max = node->last; + + if (node->rb.rb_left) { + child = rb_to_itree(node->rb.rb_left); + if (child->subtree_last > max) { + max = child->subtree_last; + } + } + if (node->rb.rb_right) { + child = rb_to_itree(node->rb.rb_right); + if (child->subtree_last > max) { + max = child->subtree_last; + } + } + if (exit && node->subtree_last == max) { + return true; + } + node->subtree_last = max; + return false; +} + +static void interval_tree_propagate(RBNode *rb, RBNode *stop) +{ + while (rb != stop) { + IntervalTreeNode *node = rb_to_itree(rb); + if (interval_tree_compute_max(node, true)) { + break; + } + rb = rb_parent(&node->rb); + } +} + +static void interval_tree_copy(RBNode *rb_old, RBNode *rb_new) +{ + IntervalTreeNode *old = rb_to_itree(rb_old); + IntervalTreeNode *new = rb_to_itree(rb_new); + + new->subtree_last = old->subtree_last; +} + +static void interval_tree_rotate(RBNode *rb_old, RBNode *rb_new) +{ + IntervalTreeNode *old = rb_to_itree(rb_old); + IntervalTreeNode *new = rb_to_itree(rb_new); + + new->subtree_last = old->subtree_last; + interval_tree_compute_max(old, false); +} + +static const RBAugmentCallbacks interval_tree_augment = { + .propagate = interval_tree_propagate, + .copy = interval_tree_copy, + .rotate = interval_tree_rotate, +}; + +/* Insert / remove interval nodes from the tree */ +void interval_tree_insert(IntervalTreeNode *node, IntervalTreeRoot *root) +{ + RBNode **link = &root->rb_root.rb_node, *rb_parent = NULL; + uint64_t start = node->start, last = node->last; + IntervalTreeNode *parent; + bool leftmost = true; + + while (*link) { + rb_parent = *link; + parent = rb_to_itree(rb_parent); + + if (parent->subtree_last < last) { + parent->subtree_last = last; + } + if (start < parent->start) { + link = &parent->rb.rb_left; + } else { + link = &parent->rb.rb_right; + leftmost = false; + } + } + + node->subtree_last = last; + rb_link_node(&node->rb, rb_parent, link); + rb_insert_augmented_cached(&node->rb, root, leftmost, + &interval_tree_augment); +} + +void interval_tree_remove(IntervalTreeNode *node, IntervalTreeRoot *root) +{ + rb_erase_augmented_cached(&node->rb, root, &interval_tree_augment); +} + +/* + * Iterate over intervals intersecting [start;last] + * + * Note that a node's interval intersects [start;last] iff: + * Cond1: node->start <= last + * and + * Cond2: start <= node->last + */ + +static IntervalTreeNode *interval_tree_subtree_search(IntervalTreeNode *node, + uint64_t start, + uint64_t last) +{ + while (true) { + /* + * Loop invariant: start <= node->subtree_last + * (Cond2 is satisfied by one of the subtree nodes) + */ + if (node->rb.rb_left) { + IntervalTreeNode *left = rb_to_itree(node->rb.rb_left); + + if (start <= left->subtree_last) { + /* + * Some nodes in left subtree satisfy Cond2. + * Iterate to find the leftmost such node N. + * If it also satisfies Cond1, that's the + * match we are looking for. Otherwise, there + * is no matching interval as nodes to the + * right of N can't satisfy Cond1 either. + */ + node = left; + continue; + } + } + if (node->start <= last) { /* Cond1 */ + if (start <= node->last) { /* Cond2 */ + return node; /* node is leftmost match */ + } + if (node->rb.rb_right) { + node = rb_to_itree(node->rb.rb_right); + if (start <= node->subtree_last) { + continue; + } + } + } + return NULL; /* no match */ + } +} + +IntervalTreeNode *interval_tree_iter_first(IntervalTreeRoot *root, + uint64_t start, uint64_t last) +{ + IntervalTreeNode *node, *leftmost; + + if (!root->rb_root.rb_node) { + return NULL; + } + + /* + * Fastpath range intersection/overlap between A: [a0, a1] and + * B: [b0, b1] is given by: + * + * a0 <= b1 && b0 <= a1 + * + * ... where A holds the lock range and B holds the smallest + * 'start' and largest 'last' in the tree. For the later, we + * rely on the root node, which by augmented interval tree + * property, holds the largest value in its last-in-subtree. + * This allows mitigating some of the tree walk overhead for + * for non-intersecting ranges, maintained and consulted in O(1). + */ + node = rb_to_itree(root->rb_root.rb_node); + if (node->subtree_last < start) { + return NULL; + } + + leftmost = rb_to_itree(root->rb_leftmost); + if (leftmost->start > last) { + return NULL; + } + + return interval_tree_subtree_search(node, start, last); +} + +IntervalTreeNode *interval_tree_iter_next(IntervalTreeNode *node, + uint64_t start, uint64_t last) +{ + RBNode *rb = node->rb.rb_right, *prev; + + while (true) { + /* + * Loop invariants: + * Cond1: node->start <= last + * rb == node->rb.rb_right + * + * First, search right subtree if suitable + */ + if (rb) { + IntervalTreeNode *right = rb_to_itree(rb); + + if (start <= right->subtree_last) { + return interval_tree_subtree_search(right, start, last); + } + } + + /* Move up the tree until we come from a node's left child */ + do { + rb = rb_parent(&node->rb); + if (!rb) { + return NULL; + } + prev = &node->rb; + node = rb_to_itree(rb); + rb = node->rb.rb_right; + } while (prev == rb); + + /* Check if the node intersects [start;last] */ + if (last < node->start) { /* !Cond1 */ + return NULL; + } + if (start <= node->last) { /* Cond2 */ + return node; + } + } +} + +/* Occasionally useful for calling from within the debugger. */ +#if 0 +static void debug_interval_tree_int(IntervalTreeNode *node, + const char *dir, int level) +{ + printf("%4d %*s %s [%" PRIu64 ",%" PRIu64 "] subtree_last:%" PRIu64 "\n", + level, level + 1, dir, rb_is_red(&node->rb) ? "r" : "b", + node->start, node->last, node->subtree_last); + + if (node->rb.rb_left) { + debug_interval_tree_int(rb_to_itree(node->rb.rb_left), "<", level + 1); + } + if (node->rb.rb_right) { + debug_interval_tree_int(rb_to_itree(node->rb.rb_right), ">", level + 1); + } +} + +void debug_interval_tree(IntervalTreeNode *node); +void debug_interval_tree(IntervalTreeNode *node) +{ + if (node) { + debug_interval_tree_int(node, "*", 0); + } else { + printf("null\n"); + } +} +#endif diff --git a/tests/unit/meson.build b/tests/unit/meson.build index b497a41378..ffa444f432 100644 --- a/tests/unit/meson.build +++ b/tests/unit/meson.build @@ -47,6 +47,7 @@ tests = { 'ptimer-test': ['ptimer-test-stubs.c', meson.project_source_root() / 'hw/core/ptimer.c'], 'test-qapi-util': [], 'test-smp-parse': [qom, meson.project_source_root() / 'hw/core/machine-smp.c'], + 'test-interval-tree': [], } if have_system or have_tools diff --git a/util/meson.build b/util/meson.build index 25b9b61f98..d8d109ff84 100644 --- a/util/meson.build +++ b/util/meson.build @@ -57,6 +57,7 @@ util_ss.add(files('guest-random.c')) util_ss.add(files('yank.c')) util_ss.add(files('int128.c')) util_ss.add(files('memalign.c')) +util_ss.add(files('interval-tree.c')) if have_user util_ss.add(files('selfmap.c'))