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Subject[PATCH v3 08/18] locking/lockdep: Define INITIAL_CHAIN_KEY for chain keys to start with
Date
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>
---
include/linux/lockdep.h | 1 +
init/init_task.c | 2 +-
kernel/locking/lockdep.c | 18 +++++++++---------
3 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 267087e..64d4565 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -224,6 +224,7 @@ struct lock_chain {
* bitfield and hitting the BUG in hlock_class().
*/
#define MAX_LOCKDEP_KEYS ((1UL << MAX_LOCKDEP_KEYS_BITS) - 1)
+#define INITIAL_CHAIN_KEY 0

struct held_lock {
/*
diff --git a/init/init_task.c b/init/init_task.c
index 9460878..ff3e8bf 100644
--- a/init/init_task.c
+++ b/init/init_task.c
@@ -166,7 +166,7 @@ struct task_struct init_task
#endif
#ifdef CONFIG_LOCKDEP
.lockdep_depth = 0, /* no locks held yet */
- .curr_chain_key = 0,
+ .curr_chain_key = INITIAL_CHAIN_KEY,
.lockdep_recursion = 0,
#endif
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index ef59651..c6363f7 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -361,7 +361,7 @@ static inline u64 iterate_chain_key(u64 key, u32 idx)
inline 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;
}

@@ -867,7 +867,7 @@ static bool class_lock_list_valid(struct lock_class *c, struct list_head *h)
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++)
@@ -2433,7 +2433,7 @@ static u64 print_chain_key_iteration(int class_idx, u64 chain_key)
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);

@@ -2453,7 +2453,7 @@ static u64 print_chain_key_iteration(int class_idx, u64 chain_key)
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);
@@ -2757,7 +2757,7 @@ 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;
@@ -2781,7 +2781,7 @@ 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;
}
@@ -3694,14 +3694,14 @@ 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);
@@ -4543,7 +4543,7 @@ 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)
--
1.8.3.1
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