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[PATCH] util/interval-tree: Avoid race conditions without optimization
From: |
Richard Henderson |
Subject: |
[PATCH] util/interval-tree: Avoid race conditions without optimization |
Date: |
Fri, 7 Jul 2023 11:30:36 +0100 |
Read the left and right trees once, so that the gating
tests are meaningful. This was only a problem at -O0,
where the compiler didn't CSE the two reads.
Cc: qemu-stable@nongnu.org
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
util/interval-tree.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/util/interval-tree.c b/util/interval-tree.c
index 4c0baf108f..31978c32ac 100644
--- a/util/interval-tree.c
+++ b/util/interval-tree.c
@@ -741,12 +741,15 @@ static IntervalTreeNode
*interval_tree_subtree_search(IntervalTreeNode *node,
uint64_t last)
{
while (true) {
+ RBNode *rb_tmp;
+
/*
* 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);
+ rb_tmp = node->rb.rb_left;
+ if (rb_tmp) {
+ IntervalTreeNode *left = rb_to_itree(rb_tmp);
if (start <= left->subtree_last) {
/*
@@ -765,8 +768,10 @@ static IntervalTreeNode
*interval_tree_subtree_search(IntervalTreeNode *node,
if (start <= node->last) { /* Cond2 */
return node; /* node is leftmost match */
}
- if (node->rb.rb_right) {
- node = rb_to_itree(node->rb.rb_right);
+
+ rb_tmp = node->rb.rb_right;
+ if (rb_tmp) {
+ node = rb_to_itree(rb_tmp);
if (start <= node->subtree_last) {
continue;
}
--
2.34.1
- [PATCH] util/interval-tree: Avoid race conditions without optimization,
Richard Henderson <=