Messages in this thread | | | From | Waiman Long <> | Subject | Re: [PATCH v2] locking/lockdep: Fix meaningless usages output of lock classes | Date | Mon, 28 Jun 2021 17:17:33 -0400 |
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On 6/28/21 11:17 AM, Xiongwei Song wrote: > From: Xiongwei Song <sxwjean@gmail.com> > > When enabling CONFIG_LOCK_STAT, then CONFIG_LOCKDEP is forcedly enabled. > We can get output from /proc/lockdep, which currently includes usages of > lock classes. But the usages are meaningless, see the output below: > > / # cat /proc/lockdep > all lock classes: > ffffffff9af63350 ....: cgroup_mutex > > ffffffff9af54eb8 ....: (console_sem).lock > > ffffffff9af54e60 ....: console_lock > > ffffffff9ae74c38 ....: console_owner_lock > > ffffffff9ae74c80 ....: console_owner > > ffffffff9ae66e60 ....: cpu_hotplug_lock > > Only one usage context for each lock, this is because each usage is only > changed in mark_lock() that is in CONFIG_PROVE_LOCKING defined section, > however in the test situation, it's not. > > The fix is to move the usages reading and seq_print from > CONFIG_PROVE_LOCKING undefined setcion to its defined section. Also, > locks_after list of lock_class is empty when CONFIG_PROVE_LOCKING > undefined, so do the same thing as what have done for usages of lock > classes. With this patch, CONFIG_LOCKDEP without CONFIG_PROVE_LOCKING will make /proc/lockdep displays just the list of lock classes with their associated lock keys. I think it is worth explicitly saying that in the commit log. > Signed-off-by: Xiongwei Song <sxwjean@gmail.com> > --- > kernel/locking/lockdep_proc.c | 24 +++++++++++++----------- > 1 file changed, 13 insertions(+), 11 deletions(-) > > diff --git a/kernel/locking/lockdep_proc.c b/kernel/locking/lockdep_proc.c > index 806978314496..a1ec2652d492 100644 > --- a/kernel/locking/lockdep_proc.c > +++ b/kernel/locking/lockdep_proc.c > @@ -70,23 +70,25 @@ static int l_show(struct seq_file *m, void *v) > #ifdef CONFIG_DEBUG_LOCKDEP > seq_printf(m, " OPS:%8ld", debug_class_ops_read(class)); > #endif > -#ifdef CONFIG_PROVE_LOCKING > - seq_printf(m, " FD:%5ld", lockdep_count_forward_deps(class)); > - seq_printf(m, " BD:%5ld", lockdep_count_backward_deps(class)); > -#endif > + if (IS_ENABLED(CONFIG_PROVE_LOCKING)) { > + seq_printf(m, " FD:%5ld", lockdep_count_forward_deps(class)); > + seq_printf(m, " BD:%5ld", lockdep_count_backward_deps(class)); > > - get_usage_chars(class, usage); > - seq_printf(m, " %s", usage); > + get_usage_chars(class, usage); > + seq_printf(m, " %s", usage); > + } > > seq_printf(m, ": "); > print_name(m, class); > seq_puts(m, "\n"); > > - list_for_each_entry(entry, &class->locks_after, entry) { > - if (entry->distance == 1) { > - seq_printf(m, " -> [%p] ", entry->class->key); > - print_name(m, entry->class); > - seq_puts(m, "\n"); > + if (IS_ENABLED(CONFIG_PROVE_LOCKING)) { > + list_for_each_entry(entry, &class->locks_after, entry) { > + if (entry->distance == 1) { > + seq_printf(m, " -> [%p] ", entry->class->key); > + print_name(m, entry->class); > + seq_puts(m, "\n"); > + } > } > } > seq_puts(m, "\n");
Maybe you can remove the blank lines in this case by moving the last seq_puts() inside the if loop. The blank lines are not really needed without the associated locks_after information.
Cheers, Longman
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