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authorLinus Torvalds <torvalds@linux-foundation.org>2015-07-01 10:49:25 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-07-01 10:49:25 -0700
commit02201e3f1b46aed7c6348f406b7b40de80ba6de3 (patch)
tree2392c9098359725c195dd82a72b20ccedc1a1509 /lib
parent0890a264794f33df540fbaf274699146903b4e6b (diff)
parent20bdc2cfdbc484777b30b96fcdbb8994038f3ce1 (diff)
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Merge tag 'modules-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux
Pull module updates from Rusty Russell: "Main excitement here is Peter Zijlstra's lockless rbtree optimization to speed module address lookup. He found some abusers of the module lock doing that too. A little bit of parameter work here too; including Dan Streetman's breaking up the big param mutex so writing a parameter can load another module (yeah, really). Unfortunately that broke the usual suspects, !CONFIG_MODULES and !CONFIG_SYSFS, so those fixes were appended too" * tag 'modules-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux: (26 commits) modules: only use mod->param_lock if CONFIG_MODULES param: fix module param locks when !CONFIG_SYSFS. rcu: merge fix for Convert ACCESS_ONCE() to READ_ONCE() and WRITE_ONCE() module: add per-module param_lock module: make perm const params: suppress unused variable error, warn once just in case code changes. modules: clarify CONFIG_MODULE_COMPRESS help, suggest 'N'. kernel/module.c: avoid ifdefs for sig_enforce declaration kernel/workqueue.c: remove ifdefs over wq_power_efficient kernel/params.c: export param_ops_bool_enable_only kernel/params.c: generalize bool_enable_only kernel/module.c: use generic module param operaters for sig_enforce kernel/params: constify struct kernel_param_ops uses sysfs: tightened sysfs permission checks module: Rework module_addr_{min,max} module: Use __module_address() for module_address_lookup() module: Make the mod_tree stuff conditional on PERF_EVENTS || TRACING module: Optimize __module_address() using a latched RB-tree rbtree: Implement generic latch_tree seqlock: Introduce raw_read_seqcount_latch() ...
Diffstat (limited to 'lib')
-rw-r--r--lib/bug.c7
-rw-r--r--lib/rbtree.c76
2 files changed, 59 insertions, 24 deletions
diff --git a/lib/bug.c b/lib/bug.c
index 0c3bd9552b6f..cff145f032a5 100644
--- a/lib/bug.c
+++ b/lib/bug.c
@@ -66,7 +66,7 @@ static const struct bug_entry *module_find_bug(unsigned long bugaddr)
struct module *mod;
const struct bug_entry *bug = NULL;
- rcu_read_lock();
+ rcu_read_lock_sched();
list_for_each_entry_rcu(mod, &module_bug_list, bug_list) {
unsigned i;
@@ -77,7 +77,7 @@ static const struct bug_entry *module_find_bug(unsigned long bugaddr)
}
bug = NULL;
out:
- rcu_read_unlock();
+ rcu_read_unlock_sched();
return bug;
}
@@ -88,6 +88,8 @@ void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
char *secstrings;
unsigned int i;
+ lockdep_assert_held(&module_mutex);
+
mod->bug_table = NULL;
mod->num_bugs = 0;
@@ -113,6 +115,7 @@ void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
void module_bug_cleanup(struct module *mod)
{
+ lockdep_assert_held(&module_mutex);
list_del_rcu(&mod->bug_list);
}
diff --git a/lib/rbtree.c b/lib/rbtree.c
index c16c81a3d430..1356454e36de 100644
--- a/lib/rbtree.c
+++ b/lib/rbtree.c
@@ -44,6 +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;
@@ -129,8 +153,9 @@ __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);
@@ -149,8 +174,8 @@ __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);
@@ -171,8 +196,9 @@ __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);
@@ -183,8 +209,8 @@ __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);
@@ -224,8 +250,9 @@ ____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);
@@ -275,9 +302,10 @@ ____rb_erase_color(struct rb_node *parent, struct rb_root *root,
* \
* 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);
@@ -297,8 +325,9 @@ ____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);
@@ -310,8 +339,9 @@ ____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);
@@ -336,9 +366,10 @@ ____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;
+ 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);
@@ -347,8 +378,9 @@ ____rb_erase_color(struct rb_node *parent, struct rb_root *root,
sibling = tmp2;
}
/* Case 4 - left rotate at parent + color flips */
- parent->rb_left = tmp2 = sibling->rb_right;
- sibling->rb_right = parent;
+ 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);