Avoid atomic operations for dependent rtree reads.
Bug: 21326736
(cherry picked from commit 831d585c1dad2e6e39804db2a223064d295cb4fe)
Change-Id: I75b5ab51aed356cfb4bff136f38f7188716717cc
diff --git a/include/jemalloc/internal/chunk.h b/include/jemalloc/internal/chunk.h
index 8093814..c253cdc 100644
--- a/include/jemalloc/internal/chunk.h
+++ b/include/jemalloc/internal/chunk.h
@@ -70,15 +70,15 @@
#ifdef JEMALLOC_H_INLINES
#ifndef JEMALLOC_ENABLE_INLINE
-extent_node_t *chunk_lookup(const void *chunk);
+extent_node_t *chunk_lookup(const void *chunk, bool dependent);
#endif
#if (defined(JEMALLOC_ENABLE_INLINE) || defined(JEMALLOC_CHUNK_C_))
JEMALLOC_INLINE extent_node_t *
-chunk_lookup(const void *chunk)
+chunk_lookup(const void *ptr, bool dependent)
{
- return (rtree_get(&chunks_rtree, (uintptr_t)chunk));
+ return (rtree_get(&chunks_rtree, (uintptr_t)ptr, dependent));
}
#endif
diff --git a/include/jemalloc/internal/jemalloc_internal.h.in b/include/jemalloc/internal/jemalloc_internal.h.in
index 910ebf7..0268245 100644
--- a/include/jemalloc/internal/jemalloc_internal.h.in
+++ b/include/jemalloc/internal/jemalloc_internal.h.in
@@ -948,7 +948,7 @@
extent_node_t *node;
/* Return 0 if ptr is not within a chunk managed by jemalloc. */
- node = chunk_lookup(CHUNK_ADDR2BASE(ptr));
+ node = chunk_lookup(ptr, false);
if (node == NULL)
return (0);
/* Only arena chunks should be looked up via interior pointers. */
diff --git a/include/jemalloc/internal/rtree.h b/include/jemalloc/internal/rtree.h
index 7a8ebfd..28ae9d1 100644
--- a/include/jemalloc/internal/rtree.h
+++ b/include/jemalloc/internal/rtree.h
@@ -114,13 +114,14 @@
rtree_node_elm_t *rtree_child_tryread(rtree_node_elm_t *elm);
rtree_node_elm_t *rtree_child_read(rtree_t *rtree, rtree_node_elm_t *elm,
unsigned level);
-extent_node_t *rtree_val_read(rtree_t *rtree, rtree_node_elm_t *elm);
+extent_node_t *rtree_val_read(rtree_t *rtree, rtree_node_elm_t *elm,
+ bool dependent);
void rtree_val_write(rtree_t *rtree, rtree_node_elm_t *elm,
const extent_node_t *val);
rtree_node_elm_t *rtree_subtree_tryread(rtree_t *rtree, unsigned level);
rtree_node_elm_t *rtree_subtree_read(rtree_t *rtree, unsigned level);
-extent_node_t *rtree_get(rtree_t *rtree, uintptr_t key);
+extent_node_t *rtree_get(rtree_t *rtree, uintptr_t key, bool dependent);
bool rtree_set(rtree_t *rtree, uintptr_t key, const extent_node_t *val);
#endif
@@ -179,10 +180,25 @@
}
JEMALLOC_INLINE extent_node_t *
-rtree_val_read(rtree_t *rtree, rtree_node_elm_t *elm)
+rtree_val_read(rtree_t *rtree, rtree_node_elm_t *elm, bool dependent)
{
- return (atomic_read_p(&elm->pun));
+ if (dependent) {
+ /*
+ * Reading a val on behalf of a pointer to a valid allocation is
+ * guaranteed to be a clean read even without synchronization,
+ * because the rtree update became visible in memory before the
+ * pointer came into existence.
+ */
+ return (elm->val);
+ } else {
+ /*
+ * An arbitrary read, e.g. on behalf of ivsalloc(), may not be
+ * dependent on a previous rtree write, which means a stale read
+ * could result if synchronization were omitted here.
+ */
+ return (atomic_read_p(&elm->pun));
+ }
}
JEMALLOC_INLINE void
@@ -216,7 +232,7 @@
}
JEMALLOC_INLINE extent_node_t *
-rtree_get(rtree_t *rtree, uintptr_t key)
+rtree_get(rtree_t *rtree, uintptr_t key, bool dependent)
{
uintptr_t subkey;
unsigned i, start_level;
@@ -226,7 +242,7 @@
for (i = start_level, node = rtree_subtree_tryread(rtree, start_level);
/**/; i++, node = child) {
- if (unlikely(!rtree_node_valid(node)))
+ if (!dependent && unlikely(!rtree_node_valid(node)))
return (NULL);
subkey = rtree_subkey(rtree, key, i);
if (i == rtree->height - 1) {
@@ -234,7 +250,8 @@
* node is a leaf, so it contains values rather than
* child pointers.
*/
- return (rtree_val_read(rtree, &node[subkey]));
+ return (rtree_val_read(rtree, &node[subkey],
+ dependent));
}
assert(i < rtree->height - 1);
child = rtree_child_tryread(&node[subkey]);
diff --git a/src/huge.c b/src/huge.c
index 32af205..6e6824d 100644
--- a/src/huge.c
+++ b/src/huge.c
@@ -8,7 +8,7 @@
{
extent_node_t *node;
- node = chunk_lookup(ptr);
+ node = chunk_lookup(ptr, true);
assert(!extent_node_achunk_get(node));
return (node);
diff --git a/test/unit/rtree.c b/test/unit/rtree.c
index 496e03a..3f95554 100644
--- a/test/unit/rtree.c
+++ b/test/unit/rtree.c
@@ -22,7 +22,7 @@
rtree_t rtree;
assert_false(rtree_new(&rtree, i, node_alloc, node_dalloc),
"Unexpected rtree_new() failure");
- assert_ptr_null(rtree_get(&rtree, 0),
+ assert_ptr_null(rtree_get(&rtree, 0, false),
"rtree_get() should return NULL for empty tree");
rtree_delete(&rtree);
}
@@ -40,11 +40,11 @@
"Unexpected rtree_new() failure");
rtree_set(&rtree, 0, &node_a);
- assert_ptr_eq(rtree_get(&rtree, 0), &node_a,
+ assert_ptr_eq(rtree_get(&rtree, 0, true), &node_a,
"rtree_get() should return previously set value");
rtree_set(&rtree, ~((uintptr_t)0), &node_b);
- assert_ptr_eq(rtree_get(&rtree, ~((uintptr_t)0)), &node_b,
+ assert_ptr_eq(rtree_get(&rtree, ~((uintptr_t)0), true), &node_b,
"rtree_get() should return previously set value");
rtree_delete(&rtree);
@@ -68,15 +68,15 @@
for (j = 0; j < sizeof(keys)/sizeof(uintptr_t); j++) {
rtree_set(&rtree, keys[j], &node);
for (k = 0; k < sizeof(keys)/sizeof(uintptr_t); k++) {
- assert_ptr_eq(rtree_get(&rtree, keys[k]), &node,
- "rtree_get() should return previously set "
- "value and ignore insignificant key bits; "
- "i=%u, j=%u, k=%u, set key=%#"PRIxPTR", "
- "get key=%#"PRIxPTR, i, j, k, keys[j],
- keys[k]);
+ assert_ptr_eq(rtree_get(&rtree, keys[k], true),
+ &node, "rtree_get() should return "
+ "previously set value and ignore "
+ "insignificant key bits; i=%u, j=%u, k=%u, "
+ "set key=%#"PRIxPTR", get key=%#"PRIxPTR, i,
+ j, k, keys[j], keys[k]);
}
assert_ptr_null(rtree_get(&rtree,
- (((uintptr_t)1) << (sizeof(uintptr_t)*8-i))),
+ (((uintptr_t)1) << (sizeof(uintptr_t)*8-i)), false),
"Only leftmost rtree leaf should be set; "
"i=%u, j=%u", i, j);
rtree_set(&rtree, keys[j], NULL);
@@ -107,21 +107,21 @@
for (j = 0; j < NSET; j++) {
keys[j] = (uintptr_t)gen_rand64(sfmt);
rtree_set(&rtree, keys[j], &node);
- assert_ptr_eq(rtree_get(&rtree, keys[j]), &node,
+ assert_ptr_eq(rtree_get(&rtree, keys[j], true), &node,
"rtree_get() should return previously set value");
}
for (j = 0; j < NSET; j++) {
- assert_ptr_eq(rtree_get(&rtree, keys[j]), &node,
+ assert_ptr_eq(rtree_get(&rtree, keys[j], true), &node,
"rtree_get() should return previously set value");
}
for (j = 0; j < NSET; j++) {
rtree_set(&rtree, keys[j], NULL);
- assert_ptr_null(rtree_get(&rtree, keys[j]),
+ assert_ptr_null(rtree_get(&rtree, keys[j], true),
"rtree_get() should return previously set value");
}
for (j = 0; j < NSET; j++) {
- assert_ptr_null(rtree_get(&rtree, keys[j]),
+ assert_ptr_null(rtree_get(&rtree, keys[j], true),
"rtree_get() should return previously set value");
}