It is not rare to spot empty lock chains in /proc/lockdep_chains, where only shows irq_context but not the locks, which is useless and makes people confused.
This happens because the chained lock classes are freeed, so consider this when printing the lock chains. Signed-off-by: Yuyang Du <[email protected]> --- kernel/locking/lockdep_proc.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/kernel/locking/lockdep_proc.c b/kernel/locking/lockdep_proc.c index 3d31f9b..47a6f4f 100644 --- a/kernel/locking/lockdep_proc.c +++ b/kernel/locking/lockdep_proc.c @@ -127,7 +127,7 @@ static int lc_show(struct seq_file *m, void *v) { struct lock_chain *chain = v; struct lock_class *class; - int i; + int i, nr_locks = 0; if (v == SEQ_START_TOKEN) { if (nr_chain_hlocks > MAX_LOCKDEP_CHAIN_HLOCKS) @@ -136,18 +136,28 @@ static int lc_show(struct seq_file *m, void *v) return 0; } - seq_printf(m, "irq_context: %d\n", chain->irq_context); - for (i = 0; i < chain->depth; i++) { class = lock_chain_get_class(chain, i); + /* + * Is this lock class zapped? + */ if (!class->key) continue; + if (!nr_locks++) + seq_printf(m, "irq_context: %d\n", chain->irq_context); + seq_printf(m, "[%p] ", class->key); print_name(m, class); seq_puts(m, "\n"); } - seq_puts(m, "\n"); + + if (nr_locks) { + if (nr_locks != chain->depth) + seq_printf(m, "(chain has %d zapped classes)\n", + chain->depth - nr_locks); + seq_puts(m, "\n"); + } return 0; } -- 1.8.3.1
