#endif /* CONFIG_DEBUG_LOCKDEP */
+static void init_chain_block_buckets(void);
+
/*
* Initialize the lock_classes[] array elements, the free_lock_classes list
* and also the delayed_free structure.
*/
static void init_data_structures_once(void)
{
- static bool ds_initialized, rcu_head_initialized;
+ static bool __read_mostly ds_initialized, rcu_head_initialized;
int i;
if (likely(rcu_head_initialized))
INIT_LIST_HEAD(&lock_classes[i].locks_after);
INIT_LIST_HEAD(&lock_classes[i].locks_before);
}
+ init_chain_block_buckets();
}
static inline struct hlist_head *keyhashentry(const struct lock_class_key *key)
static DECLARE_BITMAP(lock_chains_in_use, MAX_LOCKDEP_CHAINS);
static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
unsigned long nr_zapped_lock_chains;
-unsigned int nr_chain_hlocks;
+unsigned int nr_free_chain_hlocks; /* Free chain_hlocks in buckets */
+unsigned int nr_lost_chain_hlocks; /* Lost chain_hlocks */
+unsigned int nr_large_chain_blocks; /* size > MAX_CHAIN_BUCKETS */
+
+/*
+ * The first 2 chain_hlocks entries in the chain block in the bucket
+ * list contains the following meta data:
+ *
+ * entry[0]:
+ * Bit 15 - always set to 1 (it is not a class index)
+ * Bits 0-14 - upper 15 bits of the next block index
+ * entry[1] - lower 16 bits of next block index
+ *
+ * A next block index of all 1 bits means it is the end of the list.
+ *
+ * On the unsized bucket (bucket-0), the 3rd and 4th entries contain
+ * the chain block size:
+ *
+ * entry[2] - upper 16 bits of the chain block size
+ * entry[3] - lower 16 bits of the chain block size
+ */
+#define MAX_CHAIN_BUCKETS 16
+#define CHAIN_BLK_FLAG (1U << 15)
+#define CHAIN_BLK_LIST_END 0xFFFFU
+
+static int chain_block_buckets[MAX_CHAIN_BUCKETS];
+
+static inline int size_to_bucket(int size)
+{
+ if (size > MAX_CHAIN_BUCKETS)
+ return 0;
+
+ return size - 1;
+}
+
+/*
+ * Iterate all the chain blocks in a bucket.
+ */
+#define for_each_chain_block(bucket, prev, curr) \
+ for ((prev) = -1, (curr) = chain_block_buckets[bucket]; \
+ (curr) >= 0; \
+ (prev) = (curr), (curr) = chain_block_next(curr))
+
+/*
+ * next block or -1
+ */
+static inline int chain_block_next(int offset)
+{
+ int next = chain_hlocks[offset];
+
+ WARN_ON_ONCE(!(next & CHAIN_BLK_FLAG));
+
+ if (next == CHAIN_BLK_LIST_END)
+ return -1;
+
+ next &= ~CHAIN_BLK_FLAG;
+ next <<= 16;
+ next |= chain_hlocks[offset + 1];
+
+ return next;
+}
+
+/*
+ * bucket-0 only
+ */
+static inline int chain_block_size(int offset)
+{
+ return (chain_hlocks[offset + 2] << 16) | chain_hlocks[offset + 3];
+}
+
+static inline void init_chain_block(int offset, int next, int bucket, int size)
+{
+ chain_hlocks[offset] = (next >> 16) | CHAIN_BLK_FLAG;
+ chain_hlocks[offset + 1] = (u16)next;
+
+ if (size && !bucket) {
+ chain_hlocks[offset + 2] = size >> 16;
+ chain_hlocks[offset + 3] = (u16)size;
+ }
+}
+
+static inline void add_chain_block(int offset, int size)
+{
+ int bucket = size_to_bucket(size);
+ int next = chain_block_buckets[bucket];
+ int prev, curr;
+
+ if (unlikely(size < 2)) {
+ /*
+ * We can't store single entries on the freelist. Leak them.
+ *
+ * One possible way out would be to uniquely mark them, other
+ * than with CHAIN_BLK_FLAG, such that we can recover them when
+ * the block before it is re-added.
+ */
+ if (size)
+ nr_lost_chain_hlocks++;
+ return;
+ }
+
+ nr_free_chain_hlocks += size;
+ if (!bucket) {
+ nr_large_chain_blocks++;
+
+ /*
+ * Variable sized, sort large to small.
+ */
+ for_each_chain_block(0, prev, curr) {
+ if (size >= chain_block_size(curr))
+ break;
+ }
+ init_chain_block(offset, curr, 0, size);
+ if (prev < 0)
+ chain_block_buckets[0] = offset;
+ else
+ init_chain_block(prev, offset, 0, 0);
+ return;
+ }
+ /*
+ * Fixed size, add to head.
+ */
+ init_chain_block(offset, next, bucket, size);
+ chain_block_buckets[bucket] = offset;
+}
+
+/*
+ * Only the first block in the list can be deleted.
+ *
+ * For the variable size bucket[0], the first block (the largest one) is
+ * returned, broken up and put back into the pool. So if a chain block of
+ * length > MAX_CHAIN_BUCKETS is ever used and zapped, it will just be
+ * queued up after the primordial chain block and never be used until the
+ * hlock entries in the primordial chain block is almost used up. That
+ * causes fragmentation and reduce allocation efficiency. That can be
+ * monitored by looking at the "large chain blocks" number in lockdep_stats.
+ */
+static inline void del_chain_block(int bucket, int size, int next)
+{
+ nr_free_chain_hlocks -= size;
+ chain_block_buckets[bucket] = next;
+
+ if (!bucket)
+ nr_large_chain_blocks--;
+}
+
+static void init_chain_block_buckets(void)
+{
+ int i;
+
+ for (i = 0; i < MAX_CHAIN_BUCKETS; i++)
+ chain_block_buckets[i] = -1;
+
+ add_chain_block(0, ARRAY_SIZE(chain_hlocks));
+}
+
+/*
+ * Return offset of a chain block of the right size or -1 if not found.
+ *
+ * Fairly simple worst-fit allocator with the addition of a number of size
+ * specific free lists.
+ */
+static int alloc_chain_hlocks(int req)
+{
+ int bucket, curr, size;
+
+ /*
+ * We rely on the MSB to act as an escape bit to denote freelist
+ * pointers. Make sure this bit isn't set in 'normal' class_idx usage.
+ */
+ BUILD_BUG_ON((MAX_LOCKDEP_KEYS-1) & CHAIN_BLK_FLAG);
+
+ init_data_structures_once();
+
+ if (nr_free_chain_hlocks < req)
+ return -1;
+
+ /*
+ * We require a minimum of 2 (u16) entries to encode a freelist
+ * 'pointer'.
+ */
+ req = max(req, 2);
+ bucket = size_to_bucket(req);
+ curr = chain_block_buckets[bucket];
+
+ if (bucket) {
+ if (curr >= 0) {
+ del_chain_block(bucket, req, chain_block_next(curr));
+ return curr;
+ }
+ /* Try bucket 0 */
+ curr = chain_block_buckets[0];
+ }
+
+ /*
+ * The variable sized freelist is sorted by size; the first entry is
+ * the largest. Use it if it fits.
+ */
+ if (curr >= 0) {
+ size = chain_block_size(curr);
+ if (likely(size >= req)) {
+ del_chain_block(0, size, chain_block_next(curr));
+ add_chain_block(curr + req, size - req);
+ return curr;
+ }
+ }
+
+ /*
+ * Last resort, split a block in a larger sized bucket.
+ */
+ for (size = MAX_CHAIN_BUCKETS; size > req; size--) {
+ bucket = size_to_bucket(size);
+ curr = chain_block_buckets[bucket];
+ if (curr < 0)
+ continue;
+
+ del_chain_block(bucket, size, chain_block_next(curr));
+ add_chain_block(curr + req, size - req);
+ return curr;
+ }
+
+ return -1;
+}
+
+static inline void free_chain_hlocks(int base, int size)
+{
+ add_chain_block(base, max(size, 2));
+}
struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
{
BUILD_BUG_ON((1UL << 6) <= ARRAY_SIZE(curr->held_locks));
BUILD_BUG_ON((1UL << 8*sizeof(chain_hlocks[0])) <= ARRAY_SIZE(lock_classes));
- if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
- chain->base = nr_chain_hlocks;
- for (j = 0; j < chain->depth - 1; j++, i++) {
- int lock_id = curr->held_locks[i].class_idx;
- chain_hlocks[chain->base + j] = lock_id;
- }
- chain_hlocks[chain->base + j] = class - lock_classes;
- nr_chain_hlocks += chain->depth;
- } else {
+ j = alloc_chain_hlocks(chain->depth);
+ if (j < 0) {
if (!debug_locks_off_graph_unlock())
return 0;
return 0;
}
+ chain->base = j;
+ for (j = 0; j < chain->depth - 1; j++, i++) {
+ int lock_id = curr->held_locks[i].class_idx;
+
+ chain_hlocks[chain->base + j] = lock_id;
+ }
+ chain_hlocks[chain->base + j] = class - lock_classes;
hlist_add_head_rcu(&chain->entry, hash_head);
debug_atomic_inc(chain_lookup_misses);
inc_chains(chain->irq_context);
{
return 1;
}
+
+static void init_chain_block_buckets(void) { }
#endif /* CONFIG_PROVE_LOCKING */
/*
return;
free_lock_chain:
+ free_chain_hlocks(chain->base, chain->depth);
/* Overwrite the chain key for concurrent RCU readers. */
WRITE_ONCE(chain->chain_key, INITIAL_CHAIN_KEY);
dec_chains(chain->irq_context);
projects / linux-2.6-block.git / commitdiff