locking/lockdep: Define INITIAL_CHAIN_KEY for chain keys to start with

Chain keys are computed using Jenkins hash function, which needs an initial
hash to start with. Dedicate a macro to make this clear and configurable. A
later patch changes this initial chain key.

Signed-off-by: Yuyang Du <duyuyang@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bvanassche@acm.org
Cc: frederic@kernel.org
Cc: ming.lei@redhat.com
Cc: will.deacon@arm.com
Link: https://lkml.kernel.org/r/20190506081939.74287-9-duyuyang@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 9 insertions, 9 deletions

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index b7d9c28ecf3b..9edf6f12b711 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -362,7 +362,7 @@ static inline u64 iterate_chain_key(u64 key, u32 idx)
 void lockdep_init_task(struct task_struct *task)
 {
         task->lockdep_depth = 0; /* no locks held yet */
-        task->curr_chain_key = 0;
+        task->curr_chain_key = INITIAL_CHAIN_KEY;
         task->lockdep_recursion = 0;
 }
 
@@ -857,7 +857,7 @@ static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
 static bool check_lock_chain_key(struct lock_chain *chain)
 {
 #ifdef CONFIG_PROVE_LOCKING
-        u64 chain_key = 0;
+        u64 chain_key = INITIAL_CHAIN_KEY;
         int i;
 
         for (i = chain->base; i < chain->base + chain->depth; i++)
@@ -2524,7 +2524,7 @@ static void
 print_chain_keys_held_locks(struct task_struct *curr, struct held_lock *hlock_next)
 {
         struct held_lock *hlock;
-        u64 chain_key = 0;
+        u64 chain_key = INITIAL_CHAIN_KEY;
         int depth = curr->lockdep_depth;
         int i = get_first_held_lock(curr, hlock_next);
 
@@ -2544,7 +2544,7 @@ print_chain_keys_held_locks(struct task_struct *curr, struct held_lock *hlock_ne
 static void print_chain_keys_chain(struct lock_chain *chain)
 {
         int i;
-        u64 chain_key = 0;
+        u64 chain_key = INITIAL_CHAIN_KEY;
         int class_id;
 
         printk("depth: %u\n", chain->depth);
@@ -2848,7 +2848,7 @@ static void check_chain_key(struct task_struct *curr)
 #ifdef CONFIG_DEBUG_LOCKDEP
         struct held_lock *hlock, *prev_hlock = NULL;
         unsigned int i;
-        u64 chain_key = 0;
+        u64 chain_key = INITIAL_CHAIN_KEY;
 
         for (i = 0; i < curr->lockdep_depth; i++) {
                 hlock = curr->held_locks + i;
@@ -2872,7 +2872,7 @@ static void check_chain_key(struct task_struct *curr)
 
                 if (prev_hlock && (prev_hlock->irq_context !=
                                                         hlock->irq_context))
-                        chain_key = 0;
+                        chain_key = INITIAL_CHAIN_KEY;
                 chain_key = iterate_chain_key(chain_key, hlock->class_idx);
                 prev_hlock = hlock;
         }
@@ -3787,14 +3787,14 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
                 /*
                  * How can we have a chain hash when we ain't got no keys?!
                  */
-                if (DEBUG_LOCKS_WARN_ON(chain_key != 0))
+                if (DEBUG_LOCKS_WARN_ON(chain_key != INITIAL_CHAIN_KEY))
                         return 0;
                 chain_head = 1;
         }
 
         hlock->prev_chain_key = chain_key;
         if (separate_irq_context(curr, hlock)) {
-                chain_key = 0;
+                chain_key = INITIAL_CHAIN_KEY;
                 chain_head = 1;
         }
         chain_key = iterate_chain_key(chain_key, class_idx);
@@ -4636,7 +4636,7 @@ static void remove_class_from_lock_chain(struct pending_free *pf,
         return;
 
 recalc:
-        chain_key = 0;
+        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] + 1);
         if (chain->depth && chain->chain_key == chain_key)