diff options
author | Davidlohr Bueso <dave@stgolabs.net> | 2018-12-06 22:18:13 +0300 |
---|---|---|
committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2019-01-25 17:12:09 +0300 |
commit | 3aef2cad5d51ee66d2a614dd2f70cb34c74caf77 (patch) | |
tree | b52f1d67040ec37a2268f91061d33fa6e38e20c6 /tools | |
parent | 95420d338e2d802ea0dce4d770d3292beb587f71 (diff) | |
download | linux-3aef2cad5d51ee66d2a614dd2f70cb34c74caf77.tar.xz |
tools: Update rbtree implementation
There have been a number of changes in the kernel's rbrtee
implementation, including loose lockless searching guarantees and
rb_root_cached, which later patches will use as an optimization.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20181206191819.30182-2-dave@stgolabs.net
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools')
-rw-r--r-- | tools/include/linux/rbtree.h | 52 | ||||
-rw-r--r-- | tools/include/linux/rbtree_augmented.h | 60 | ||||
-rw-r--r-- | tools/lib/rbtree.c | 178 |
3 files changed, 229 insertions, 61 deletions
diff --git a/tools/include/linux/rbtree.h b/tools/include/linux/rbtree.h index 112582253dd0..8e9ed4786269 100644 --- a/tools/include/linux/rbtree.h +++ b/tools/include/linux/rbtree.h @@ -43,13 +43,28 @@ struct rb_root { struct rb_node *rb_node; }; +/* + * Leftmost-cached rbtrees. + * + * We do not cache the rightmost node based on footprint + * size vs number of potential users that could benefit + * from O(1) rb_last(). Just not worth it, users that want + * this feature can always implement the logic explicitly. + * Furthermore, users that want to cache both pointers may + * find it a bit asymmetric, but that's ok. + */ +struct rb_root_cached { + struct rb_root rb_root; + struct rb_node *rb_leftmost; +}; #define rb_parent(r) ((struct rb_node *)((r)->__rb_parent_color & ~3)) #define RB_ROOT (struct rb_root) { NULL, } +#define RB_ROOT_CACHED (struct rb_root_cached) { {NULL, }, NULL } #define rb_entry(ptr, type, member) container_of(ptr, type, member) -#define RB_EMPTY_ROOT(root) ((root)->rb_node == NULL) +#define RB_EMPTY_ROOT(root) (READ_ONCE((root)->rb_node) == NULL) /* 'empty' nodes are nodes that are known not to be inserted in an rbtree */ #define RB_EMPTY_NODE(node) \ @@ -68,6 +83,12 @@ extern struct rb_node *rb_prev(const struct rb_node *); extern struct rb_node *rb_first(const struct rb_root *); extern struct rb_node *rb_last(const struct rb_root *); +extern void rb_insert_color_cached(struct rb_node *, + struct rb_root_cached *, bool); +extern void rb_erase_cached(struct rb_node *node, struct rb_root_cached *); +/* Same as rb_first(), but O(1) */ +#define rb_first_cached(root) (root)->rb_leftmost + /* Postorder iteration - always visit the parent after its children */ extern struct rb_node *rb_first_postorder(const struct rb_root *); extern struct rb_node *rb_next_postorder(const struct rb_node *); @@ -75,6 +96,8 @@ extern struct rb_node *rb_next_postorder(const struct rb_node *); /* Fast replacement of a single node without remove/rebalance/add/rebalance */ extern void rb_replace_node(struct rb_node *victim, struct rb_node *new, struct rb_root *root); +extern void rb_replace_node_cached(struct rb_node *victim, struct rb_node *new, + struct rb_root_cached *root); static inline void rb_link_node(struct rb_node *node, struct rb_node *parent, struct rb_node **rb_link) @@ -90,12 +113,29 @@ static inline void rb_link_node(struct rb_node *node, struct rb_node *parent, ____ptr ? rb_entry(____ptr, type, member) : NULL; \ }) - -/* - * Handy for checking that we are not deleting an entry that is - * already in a list, found in block/{blk-throttle,cfq-iosched}.c, - * probably should be moved to lib/rbtree.c... +/** + * rbtree_postorder_for_each_entry_safe - iterate in post-order over rb_root of + * given type allowing the backing memory of @pos to be invalidated + * + * @pos: the 'type *' to use as a loop cursor. + * @n: another 'type *' to use as temporary storage + * @root: 'rb_root *' of the rbtree. + * @field: the name of the rb_node field within 'type'. + * + * rbtree_postorder_for_each_entry_safe() provides a similar guarantee as + * list_for_each_entry_safe() and allows the iteration to continue independent + * of changes to @pos by the body of the loop. + * + * Note, however, that it cannot handle other modifications that re-order the + * rbtree it is iterating over. This includes calling rb_erase() on @pos, as + * rb_erase() may rebalance the tree, causing us to miss some nodes. */ +#define rbtree_postorder_for_each_entry_safe(pos, n, root, field) \ + for (pos = rb_entry_safe(rb_first_postorder(root), typeof(*pos), field); \ + pos && ({ n = rb_entry_safe(rb_next_postorder(&pos->field), \ + typeof(*pos), field); 1; }); \ + pos = n) + static inline void rb_erase_init(struct rb_node *n, struct rb_root *root) { rb_erase(n, root); diff --git a/tools/include/linux/rbtree_augmented.h b/tools/include/linux/rbtree_augmented.h index 43be941db695..d008e1404580 100644 --- a/tools/include/linux/rbtree_augmented.h +++ b/tools/include/linux/rbtree_augmented.h @@ -44,7 +44,9 @@ struct rb_augment_callbacks { void (*rotate)(struct rb_node *old, struct rb_node *new); }; -extern void __rb_insert_augmented(struct rb_node *node, struct rb_root *root, +extern void __rb_insert_augmented(struct rb_node *node, + struct rb_root *root, + bool newleft, struct rb_node **leftmost, void (*augment_rotate)(struct rb_node *old, struct rb_node *new)); /* * Fixup the rbtree and update the augmented information when rebalancing. @@ -60,7 +62,16 @@ static inline void rb_insert_augmented(struct rb_node *node, struct rb_root *root, const struct rb_augment_callbacks *augment) { - __rb_insert_augmented(node, root, augment->rotate); + __rb_insert_augmented(node, root, false, NULL, augment->rotate); +} + +static inline void +rb_insert_augmented_cached(struct rb_node *node, + struct rb_root_cached *root, bool newleft, + const struct rb_augment_callbacks *augment) +{ + __rb_insert_augmented(node, &root->rb_root, + newleft, &root->rb_leftmost, augment->rotate); } #define RB_DECLARE_CALLBACKS(rbstatic, rbname, rbstruct, rbfield, \ @@ -93,7 +104,9 @@ rbname ## _rotate(struct rb_node *rb_old, struct rb_node *rb_new) \ old->rbaugmented = rbcompute(old); \ } \ rbstatic const struct rb_augment_callbacks rbname = { \ - rbname ## _propagate, rbname ## _copy, rbname ## _rotate \ + .propagate = rbname ## _propagate, \ + .copy = rbname ## _copy, \ + .rotate = rbname ## _rotate \ }; @@ -126,11 +139,11 @@ __rb_change_child(struct rb_node *old, struct rb_node *new, { if (parent) { if (parent->rb_left == old) - parent->rb_left = new; + WRITE_ONCE(parent->rb_left, new); else - parent->rb_right = new; + WRITE_ONCE(parent->rb_right, new); } else - root->rb_node = new; + WRITE_ONCE(root->rb_node, new); } extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root, @@ -138,12 +151,17 @@ extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root, static __always_inline struct rb_node * __rb_erase_augmented(struct rb_node *node, struct rb_root *root, + struct rb_node **leftmost, const struct rb_augment_callbacks *augment) { - struct rb_node *child = node->rb_right, *tmp = node->rb_left; + struct rb_node *child = node->rb_right; + struct rb_node *tmp = node->rb_left; struct rb_node *parent, *rebalance; unsigned long pc; + if (leftmost && node == *leftmost) + *leftmost = rb_next(node); + if (!tmp) { /* * Case 1: node to erase has no more than 1 child (easy!) @@ -170,6 +188,7 @@ __rb_erase_augmented(struct rb_node *node, struct rb_root *root, tmp = parent; } else { struct rb_node *successor = child, *child2; + tmp = child->rb_left; if (!tmp) { /* @@ -183,6 +202,7 @@ __rb_erase_augmented(struct rb_node *node, struct rb_root *root, */ parent = successor; child2 = successor->rb_right; + augment->copy(node, successor); } else { /* @@ -204,19 +224,23 @@ __rb_erase_augmented(struct rb_node *node, struct rb_root *root, successor = tmp; tmp = tmp->rb_left; } while (tmp); - parent->rb_left = child2 = successor->rb_right; - successor->rb_right = child; + child2 = successor->rb_right; + WRITE_ONCE(parent->rb_left, child2); + WRITE_ONCE(successor->rb_right, child); rb_set_parent(child, successor); + augment->copy(node, successor); augment->propagate(parent, successor); } - successor->rb_left = tmp = node->rb_left; + tmp = node->rb_left; + WRITE_ONCE(successor->rb_left, tmp); rb_set_parent(tmp, successor); pc = node->__rb_parent_color; tmp = __rb_parent(pc); __rb_change_child(node, successor, tmp, root); + if (child2) { successor->__rb_parent_color = pc; rb_set_parent_color(child2, parent, RB_BLACK); @@ -237,9 +261,21 @@ static __always_inline void rb_erase_augmented(struct rb_node *node, struct rb_root *root, const struct rb_augment_callbacks *augment) { - struct rb_node *rebalance = __rb_erase_augmented(node, root, augment); + struct rb_node *rebalance = __rb_erase_augmented(node, root, + NULL, augment); if (rebalance) __rb_erase_color(rebalance, root, augment->rotate); } -#endif /* _TOOLS_LINUX_RBTREE_AUGMENTED_H */ +static __always_inline void +rb_erase_augmented_cached(struct rb_node *node, struct rb_root_cached *root, + const struct rb_augment_callbacks *augment) +{ + struct rb_node *rebalance = __rb_erase_augmented(node, &root->rb_root, + &root->rb_leftmost, + augment); + if (rebalance) + __rb_erase_color(rebalance, &root->rb_root, augment->rotate); +} + +#endif /* _TOOLS_LINUX_RBTREE_AUGMENTED_H */ diff --git a/tools/lib/rbtree.c b/tools/lib/rbtree.c index 17c2b596f043..904adb70a4f0 100644 --- a/tools/lib/rbtree.c +++ b/tools/lib/rbtree.c @@ -22,6 +22,7 @@ */ #include <linux/rbtree_augmented.h> +#include <linux/export.h> /* * red-black trees properties: http://en.wikipedia.org/wiki/Rbtree @@ -43,6 +44,30 @@ * 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(). 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. + */ + static inline void rb_set_black(struct rb_node *rb) { rb->__rb_parent_color |= RB_BLACK; @@ -70,22 +95,35 @@ __rb_rotate_set_parents(struct rb_node *old, struct rb_node *new, static __always_inline void __rb_insert(struct rb_node *node, struct rb_root *root, + bool newleft, struct rb_node **leftmost, void (*augment_rotate)(struct rb_node *old, struct rb_node *new)) { struct rb_node *parent = rb_red_parent(node), *gparent, *tmp; + if (newleft) + *leftmost = node; + while (true) { /* - * Loop invariant: node is red - * - * If there is a black parent, we are done. - * Otherwise, take some corrective action as we don't - * want a red root or two consecutive red nodes. + * Loop invariant: node is red. */ - if (!parent) { + 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; - } else if (rb_is_black(parent)) + } + + /* + * 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); @@ -94,7 +132,7 @@ __rb_insert(struct rb_node *node, struct rb_root *root, if (parent != tmp) { /* parent == gparent->rb_left */ if (tmp && rb_is_red(tmp)) { /* - * Case 1 - color flips + * Case 1 - node's uncle is red (color flips). * * G g * / \ / \ @@ -117,7 +155,8 @@ __rb_insert(struct rb_node *node, struct rb_root *root, tmp = parent->rb_right; if (node == tmp) { /* - * Case 2 - left rotate at parent + * Case 2 - node's uncle is black and node is + * the parent's right child (left rotate at parent). * * G G * / \ / \ @@ -128,8 +167,9 @@ __rb_insert(struct rb_node *node, struct rb_root *root, * This still leaves us in violation of 4), the * continuation into Case 3 will fix that. */ - parent->rb_right = tmp = node->rb_left; - node->rb_left = parent; + tmp = node->rb_left; + WRITE_ONCE(parent->rb_right, tmp); + WRITE_ONCE(node->rb_left, parent); if (tmp) rb_set_parent_color(tmp, parent, RB_BLACK); @@ -140,7 +180,8 @@ __rb_insert(struct rb_node *node, struct rb_root *root, } /* - * Case 3 - right rotate at gparent + * Case 3 - node's uncle is black and node is + * the parent's left child (right rotate at gparent). * * G P * / \ / \ @@ -148,8 +189,8 @@ __rb_insert(struct rb_node *node, struct rb_root *root, * / \ * n U */ - gparent->rb_left = tmp; /* == parent->rb_right */ - parent->rb_right = gparent; + WRITE_ONCE(gparent->rb_left, tmp); /* == parent->rb_right */ + WRITE_ONCE(parent->rb_right, gparent); if (tmp) rb_set_parent_color(tmp, gparent, RB_BLACK); __rb_rotate_set_parents(gparent, parent, root, RB_RED); @@ -170,8 +211,9 @@ __rb_insert(struct rb_node *node, struct rb_root *root, tmp = parent->rb_left; if (node == tmp) { /* Case 2 - right rotate at parent */ - parent->rb_left = tmp = node->rb_right; - node->rb_right = parent; + tmp = node->rb_right; + WRITE_ONCE(parent->rb_left, tmp); + WRITE_ONCE(node->rb_right, parent); if (tmp) rb_set_parent_color(tmp, parent, RB_BLACK); @@ -182,8 +224,8 @@ __rb_insert(struct rb_node *node, struct rb_root *root, } /* Case 3 - left rotate at gparent */ - gparent->rb_right = tmp; /* == parent->rb_left */ - parent->rb_left = gparent; + WRITE_ONCE(gparent->rb_right, tmp); /* == parent->rb_left */ + WRITE_ONCE(parent->rb_left, gparent); if (tmp) rb_set_parent_color(tmp, gparent, RB_BLACK); __rb_rotate_set_parents(gparent, parent, root, RB_RED); @@ -223,8 +265,9 @@ ____rb_erase_color(struct rb_node *parent, struct rb_root *root, * / \ / \ * Sl Sr N Sl */ - parent->rb_right = tmp1 = sibling->rb_left; - sibling->rb_left = parent; + tmp1 = sibling->rb_left; + WRITE_ONCE(parent->rb_right, tmp1); + WRITE_ONCE(sibling->rb_left, parent); rb_set_parent_color(tmp1, parent, RB_BLACK); __rb_rotate_set_parents(parent, sibling, root, RB_RED); @@ -268,15 +311,31 @@ ____rb_erase_color(struct rb_node *parent, struct rb_root *root, * * (p) (p) * / \ / \ - * N S --> N Sl + * N S --> N sl * / \ \ - * sl Sr s + * sl Sr S * \ * Sr + * + * Note: p might be red, and then both + * 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 */ - sibling->rb_left = tmp1 = tmp2->rb_right; - tmp2->rb_right = sibling; - parent->rb_right = tmp2; + tmp1 = tmp2->rb_right; + WRITE_ONCE(sibling->rb_left, tmp1); + WRITE_ONCE(tmp2->rb_right, sibling); + WRITE_ONCE(parent->rb_right, tmp2); if (tmp1) rb_set_parent_color(tmp1, sibling, RB_BLACK); @@ -296,8 +355,9 @@ ____rb_erase_color(struct rb_node *parent, struct rb_root *root, * / \ / \ * (sl) sr N (sl) */ - parent->rb_right = tmp2 = sibling->rb_left; - sibling->rb_left = parent; + tmp2 = sibling->rb_left; + WRITE_ONCE(parent->rb_right, tmp2); + WRITE_ONCE(sibling->rb_left, parent); rb_set_parent_color(tmp1, sibling, RB_BLACK); if (tmp2) rb_set_parent(tmp2, parent); @@ -309,8 +369,9 @@ ____rb_erase_color(struct rb_node *parent, struct rb_root *root, sibling = parent->rb_left; if (rb_is_red(sibling)) { /* Case 1 - right rotate at parent */ - parent->rb_left = tmp1 = sibling->rb_right; - sibling->rb_right = parent; + tmp1 = sibling->rb_right; + WRITE_ONCE(parent->rb_left, tmp1); + WRITE_ONCE(sibling->rb_right, parent); rb_set_parent_color(tmp1, parent, RB_BLACK); __rb_rotate_set_parents(parent, sibling, root, RB_RED); @@ -334,10 +395,11 @@ ____rb_erase_color(struct rb_node *parent, struct rb_root *root, } break; } - /* Case 3 - right rotate at sibling */ - sibling->rb_right = tmp1 = tmp2->rb_left; - tmp2->rb_left = sibling; - parent->rb_left = tmp2; + /* Case 3 - left rotate at sibling */ + tmp1 = tmp2->rb_left; + WRITE_ONCE(sibling->rb_right, tmp1); + WRITE_ONCE(tmp2->rb_left, sibling); + WRITE_ONCE(parent->rb_left, tmp2); if (tmp1) rb_set_parent_color(tmp1, sibling, RB_BLACK); @@ -345,9 +407,10 @@ ____rb_erase_color(struct rb_node *parent, struct rb_root *root, tmp1 = sibling; sibling = tmp2; } - /* Case 4 - left rotate at parent + color flips */ - parent->rb_left = tmp2 = sibling->rb_right; - sibling->rb_right = parent; + /* Case 4 - right rotate at parent + color flips */ + tmp2 = sibling->rb_right; + WRITE_ONCE(parent->rb_left, tmp2); + WRITE_ONCE(sibling->rb_right, parent); rb_set_parent_color(tmp1, sibling, RB_BLACK); if (tmp2) rb_set_parent(tmp2, parent); @@ -378,22 +441,41 @@ static inline void dummy_copy(struct rb_node *old, struct rb_node *new) {} static inline void dummy_rotate(struct rb_node *old, struct rb_node *new) {} static const struct rb_augment_callbacks dummy_callbacks = { - dummy_propagate, dummy_copy, dummy_rotate + .propagate = dummy_propagate, + .copy = dummy_copy, + .rotate = dummy_rotate }; void rb_insert_color(struct rb_node *node, struct rb_root *root) { - __rb_insert(node, root, dummy_rotate); + __rb_insert(node, root, false, NULL, dummy_rotate); } void rb_erase(struct rb_node *node, struct rb_root *root) { struct rb_node *rebalance; - rebalance = __rb_erase_augmented(node, root, &dummy_callbacks); + rebalance = __rb_erase_augmented(node, root, + NULL, &dummy_callbacks); if (rebalance) ____rb_erase_color(rebalance, root, dummy_rotate); } +void rb_insert_color_cached(struct rb_node *node, + struct rb_root_cached *root, bool leftmost) +{ + __rb_insert(node, &root->rb_root, leftmost, + &root->rb_leftmost, dummy_rotate); +} + +void rb_erase_cached(struct rb_node *node, struct rb_root_cached *root) +{ + struct rb_node *rebalance; + rebalance = __rb_erase_augmented(node, &root->rb_root, + &root->rb_leftmost, &dummy_callbacks); + if (rebalance) + ____rb_erase_color(rebalance, &root->rb_root, dummy_rotate); +} + /* * Augmented rbtree manipulation functions. * @@ -402,9 +484,10 @@ void rb_erase(struct rb_node *node, struct rb_root *root) */ void __rb_insert_augmented(struct rb_node *node, struct rb_root *root, + bool newleft, struct rb_node **leftmost, void (*augment_rotate)(struct rb_node *old, struct rb_node *new)) { - __rb_insert(node, root, augment_rotate); + __rb_insert(node, root, newleft, leftmost, augment_rotate); } /* @@ -498,15 +581,24 @@ void rb_replace_node(struct rb_node *victim, struct rb_node *new, { struct rb_node *parent = rb_parent(victim); + /* Copy the pointers/colour from the victim to the replacement */ + *new = *victim; + /* Set the surrounding nodes to point to the replacement */ - __rb_change_child(victim, new, parent, root); if (victim->rb_left) rb_set_parent(victim->rb_left, new); if (victim->rb_right) rb_set_parent(victim->rb_right, new); + __rb_change_child(victim, new, parent, root); +} - /* Copy the pointers/colour from the victim to the replacement */ - *new = *victim; +void rb_replace_node_cached(struct rb_node *victim, struct rb_node *new, + struct rb_root_cached *root) +{ + rb_replace_node(victim, new, &root->rb_root); + + if (root->rb_leftmost == victim) + root->rb_leftmost = new; } static struct rb_node *rb_left_deepest_node(const struct rb_node *node) |