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Commit 3aef2cad authored by Davidlohr Bueso's avatar Davidlohr Bueso Committed by Arnaldo Carvalho de Melo
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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: default avatarDavidlohr Bueso <dbueso@suse.de>
Tested-by: default avatarArnaldo 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.netSigned-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 95420d33
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Showing with 229 additions and 61 deletions
tools/include/linux/rbtree.h
View file @ 3aef2cad
......@@ -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);
......
tools/include/linux/rbtree_augmented.h
View file @ 3aef2cad
......@@ -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);
}
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 */
tools/lib/rbtree.c
View file @ 3aef2cad
......@@ -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 (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).
*/
if (!parent) {
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)
......
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