[PATCH 09/17] locking/lockdep: Hash held lock's read-write type into chain key

Yuyang Du
2019-05-13T09:13:51Z

When computing a chain's hash key, we need to consider a held lock's type,
so the additional data to use Jenkins hash algorithm is a composite of the
new held lock's lock class index (lower 16 bits) and its read-write type
(higher 16 bits) as opposed to just class index before:

held lock type (u16) : lock class index (u16)

Signed-off-by: Yuyang Du <duyuyang@gmail.com>
---
kernel/locking/lockdep.c | 46 ++++++++++++++++++++++++++++++++--------------
1 file changed, 32 insertions(+), 14 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 0456f75..fed5d11 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -359,11 +359,19 @@ struct pending_free {
* it's a hash of all locks taken up to that lock, including that lock.
* It's a 64-bit hash, because it's important for the keys to be
* unique.
+ *
+ * The additional u32 data to hash is a composite of the new held lock's
+ * lock class index (lower 16 bits) and its read-write type (higher 16
+ * bits):
+ *
+ * hlock type (u16) : lock class index (u16)
*/
-static inline u64 iterate_chain_key(u64 key, u32 idx)
+static inline u64 iterate_chain_key(u64 key, u32 idx, u16 hlock_type)
{
u32 k0 = key, k1 = key >> 32;

+ idx += hlock_type << LOCK_TYPE_BITS;
+
__jhash_mix(idx, k0, k1); /* Macro that modifies arguments! */

return k0 | (u64)k1 << 32;
@@ -871,7 +879,8 @@ static bool check_lock_chain_key(struct lock_chain *chain)
int i;

for (i = chain->base; i < chain->base + chain->depth; i++)
- chain_key = iterate_chain_key(chain_key, chain_hlocks[i]);
+ chain_key = iterate_chain_key(chain_key, chain_hlocks[i],
+ chain_hlocks_type[i]);
/*
* The 'unsigned long long' casts avoid that a compiler warning
* is reported when building tools/lib/lockdep.
@@ -2699,9 +2708,9 @@ static inline int get_first_held_lock(struct task_struct *curr,
/*
* Returns the next chain_key iteration
*/
-static u64 print_chain_key_iteration(int class_idx, u64 chain_key)
+static u64 print_chain_key_iteration(int class_idx, u64 chain_key, int lock_type)
{
- u64 new_chain_key = iterate_chain_key(chain_key, class_idx);
+ u64 new_chain_key = iterate_chain_key(chain_key, class_idx, lock_type);

printk(" class_idx:%d -> chain_key:%016Lx",
class_idx,
@@ -2721,12 +2730,15 @@ static u64 print_chain_key_iteration(int class_idx, u64 chain_key)
hlock_next->irq_context);
for (; i < depth; i++) {
hlock = curr->held_locks + i;
- chain_key = print_chain_key_iteration(hlock->class_idx, chain_key);
+ chain_key = print_chain_key_iteration(hlock->class_idx,
+ chain_key,
+ hlock->read);

print_lock(hlock);
}

- print_chain_key_iteration(hlock_next->class_idx, chain_key);
+ print_chain_key_iteration(hlock_next->class_idx, chain_key,
+ hlock_next->read);
print_lock(hlock_next);
}

@@ -2734,12 +2746,14 @@ static void print_chain_keys_chain(struct lock_chain *chain)
{
int i;
u64 chain_key = INITIAL_CHAIN_KEY;
- int class_id;
+ int class_id, lock_type;

printk("depth: %u\n", chain->depth);
for (i = 0; i < chain->depth; i++) {
class_id = chain_hlocks[chain->base + i];
- chain_key = print_chain_key_iteration(class_id, chain_key);
+ lock_type = chain_hlocks_type[chain->base + i];
+ chain_key = print_chain_key_iteration(class_id, chain_key,
+ lock_type);

print_lock_name(lock_classes + class_id);
printk("\n");
@@ -2780,7 +2794,7 @@ static int check_no_collision(struct task_struct *curr,
struct lock_chain *chain)
{
#ifdef CONFIG_DEBUG_LOCKDEP
- int i, j, id;
+ int i, j, id, type;

i = get_first_held_lock(curr, hlock);

@@ -2789,10 +2803,12 @@ static int check_no_collision(struct task_struct *curr,
return 0;
}

- for (j = 0; j < chain->depth - 1; j++, i++) {
+ for (j = chain->base; j < chain->base + chain->depth - 1; j++, i++) {
id = curr->held_locks[i].class_idx;
+ type = curr->held_locks[i].read;

- if (DEBUG_LOCKS_WARN_ON(chain_hlocks[chain->base + j] != id)) {
+ if (DEBUG_LOCKS_WARN_ON((chain_hlocks[j] != id) ||
+ (chain_hlocks_type[j] != type))) {
print_collision(curr, hlock, chain);
return 0;
}
@@ -3078,7 +3094,8 @@ static void check_chain_key(struct task_struct *curr)
if (prev_hlock && (prev_hlock->irq_context !=
hlock->irq_context))
chain_key = INITIAL_CHAIN_KEY;
- chain_key = iterate_chain_key(chain_key, hlock->class_idx);
+ chain_key = iterate_chain_key(chain_key, hlock->class_idx,
+ hlock->read);
prev_hlock = hlock;
}
if (chain_key != curr->curr_chain_key) {
@@ -4001,7 +4018,7 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
chain_key = INITIAL_CHAIN_KEY;
chain_head = 1;
}
- chain_key = iterate_chain_key(chain_key, class_idx);
+ chain_key = iterate_chain_key(chain_key, class_idx, read);

if (nest_lock && !__lock_is_held(nest_lock, -1)) {
print_lock_nested_lock_not_held(curr, hlock, ip);
@@ -4845,7 +4862,8 @@ static void remove_class_from_lock_chain(struct pending_free *pf,
recalc:
chain_key = INITIAL_CHAIN_KEY;
for (i = chain->base; i < chain->base + chain->depth; i++)
- chain_key = iterate_chain_key(chain_key, chain_hlocks[i]);
+ chain_key = iterate_chain_key(chain_key, chain_hlocks[i],
+ chain_hlocks_type[i]);
if (chain->depth && chain->chain_key == chain_key)
return;
/* Overwrite the chain key for concurrent RCU readers. */
--
1.8.3.1