Currently, lockdep only has limit support for deadlock detection for recursive read locks.
The basic idea of the detection is: Since we make __bfs() able to traverse only the strong dependency paths, so we report a circular deadlock if we could find a circle of a strong dependency path. Signed-off-by: Boqun Feng <[email protected]> --- kernel/locking/lockdep.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 150a24abd343..e3bd872cc3ec 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -1338,6 +1338,14 @@ static inline int class_equal(struct lock_list *entry, void *data) return entry->class == data; } +static inline int hlock_conflict(struct lock_list *entry, void *data) +{ + struct held_lock *hlock = (struct held_lock *)data; + + return hlock_class(hlock) == entry->class && + (hlock->read != 2 || !entry->is_rr); +} + static noinline int print_circular_bug(struct lock_list *this, struct lock_list *target, struct held_lock *check_src, @@ -1450,18 +1458,18 @@ unsigned long lockdep_count_backward_deps(struct lock_class *class) } /* - * Prove that the dependency graph starting at <entry> can not + * Prove that the dependency graph starting at <root> can not * lead to <target>. Print an error and return BFS_RMATCH if it does. */ static noinline enum bfs_result -check_noncircular(struct lock_list *root, struct lock_class *target, +check_noncircular(struct lock_list *root, struct held_lock *target, struct lock_list **target_entry) { enum bfs_result result; debug_atomic_inc(nr_cyclic_checks); - result = __bfs_forwards(root, target, class_equal, target_entry); + result = __bfs_forwards(root, target, hlock_conflict, target_entry); return result; } @@ -1989,7 +1997,7 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev, * keep the stackframe size of the recursive functions low: */ bfs_init_root(&this, next); - ret = check_noncircular(&this, hlock_class(prev), &target_entry); + ret = check_noncircular(&this, prev, &target_entry); if (unlikely(ret == BFS_RMATCH)) { if (!trace->entries) { /* -- 2.15.1
