Commit ce07a941 authored by Byungchul Park's avatar Byungchul Park Committed by Ingo Molnar

locking/lockdep: Make check_prev_add() able to handle external stack_trace

Currently, a space for stack_trace is pinned in check_prev_add(), that
makes us not able to use external stack_trace. The simplest way to
achieve it is to pass an external stack_trace as an argument.

A more suitable solution is to pass a callback additionally along with
a stack_trace so that callers can decide the way to save or whether to
save. Actually crossrelease needs to do other than saving a stack_trace.
So pass a stack_trace and callback to handle it, to check_prev_add().
Signed-off-by: default avatarByungchul Park <>
Signed-off-by: default avatarPeter Zijlstra (Intel) <>
Cc: Linus Torvalds <>
Cc: Peter Zijlstra <>
Cc: Thomas Gleixner <>
Link: default avatarIngo Molnar <>
parent 70911fdc
......@@ -1824,20 +1824,13 @@ check_deadlock(struct task_struct *curr, struct held_lock *next,
static int
check_prev_add(struct task_struct *curr, struct held_lock *prev,
struct held_lock *next, int distance, int *stack_saved)
struct held_lock *next, int distance, struct stack_trace *trace,
int (*save)(struct stack_trace *trace))
struct lock_list *entry;
int ret;
struct lock_list this;
struct lock_list *uninitialized_var(target_entry);
* Static variable, serialized by the graph_lock().
* We use this static variable to save the stack trace in case
* we call into this function multiple times due to encountering
* trylocks in the held lock stack.
static struct stack_trace trace;
* Prove that the new <prev> -> <next> dependency would not
......@@ -1899,11 +1892,8 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
return print_bfs_bug(ret);
if (!*stack_saved) {
if (!save_trace(&trace))
return 0;
*stack_saved = 1;
if (save && !save(trace))
return 0;
* Ok, all validations passed, add the new lock
......@@ -1911,14 +1901,14 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
ret = add_lock_to_list(hlock_class(next),
next->acquire_ip, distance, &trace);
next->acquire_ip, distance, trace);
if (!ret)
return 0;
ret = add_lock_to_list(hlock_class(prev),
next->acquire_ip, distance, &trace);
next->acquire_ip, distance, trace);
if (!ret)
return 0;
......@@ -1926,8 +1916,6 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
* Debugging printouts:
if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
/* We drop graph lock, so another thread can overwrite trace. */
*stack_saved = 0;
printk("\n new dependency: ");
......@@ -1951,8 +1939,9 @@ static int
check_prevs_add(struct task_struct *curr, struct held_lock *next)
int depth = curr->lockdep_depth;
int stack_saved = 0;
struct held_lock *hlock;
struct stack_trace trace;
int (*save)(struct stack_trace *trace) = save_trace;
* Debugging checks.
......@@ -1977,9 +1966,18 @@ check_prevs_add(struct task_struct *curr, struct held_lock *next)
* added:
if (hlock->read != 2 && hlock->check) {
if (!check_prev_add(curr, hlock, next,
distance, &stack_saved))
int ret = check_prev_add(curr, hlock, next,
distance, &trace, save);
if (!ret)
return 0;
* Stop saving stack_trace if save_trace() was
* called at least once:
if (save && ret == 2)
save = NULL;
* Stop after the first non-trylock entry,
* as non-trylock entries have added their
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