On Sat, May 28, 2016 at 03:57:19PM -0400, George Spelvin wrote:
> +static inline unsigned int fold_hash(unsigned long x, unsigned long y)
> {
> + y ^= x * GOLDEN_RATIO_64;
> + y *= GOLDEN_RATIO_64;
> + return y >> 32;
> }
So does it make sense to use that pattern here too?
This code doesn't much care about performance, but wants a decent hash
from the stack of class keys.
---
kernel/locking/lockdep.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 81f1a7107c0e..c8498efcd5d9 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -309,10 +309,12 @@ static struct hlist_head chainhash_table[CHAINHASH_SIZE];
* It's a 64-bit hash, because it's important for the keys to be
* unique.
*/
-#define iterate_chain_key(key1, key2) \
- (((key1) << MAX_LOCKDEP_KEYS_BITS) ^ \
- ((key1) >> (64-MAX_LOCKDEP_KEYS_BITS)) ^ \
- (key2))
+static inline u64 iterate_chain_key(u64 x, u64 y)
+{
+ y ^= x * GOLDEN_RATIO_64;
+ y *= GOLDEN_RATIO_64;
+ return y;
+}
void lockdep_off(void)
{
