The following commit has been merged into the locking/urgent branch of tip: Commit-ID: a23fb0cfa911423327e5a2089d33ab6cddc6a6aa Gitweb: https://git.kernel.org/tip/a23fb0cfa911423327e5a2089d33ab6cddc6a6aa Author: Xiongwei Song <sxwjean@xxxxxxxxx> AuthorDate: Tue, 29 Jun 2021 21:59:16 +08:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Fri, 02 Jul 2021 15:58:26 +02:00 locking/lockdep: Fix meaningless usages output of lock classes 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 with CONFIG_PROVE_LOCKING undefined, we can get the results below: / # cat /proc/lockdep all lock classes: ffffffff85163290: cgroup_mutex ffffffff85154dd8: (console_sem).lock ffffffff85154d80: console_lock ffffffff85074b58: console_owner_lock ffffffff85074ba0: console_owner ffffffff85066d60: cpu_hotplug_lock a class key and the relevant class name each line. Signed-off-by: Xiongwei Song <sxwjean@xxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Acked-by: Waiman Long <longman@xxxxxxxxxx> Link: https://lore.kernel.org/r/20210629135916.308210-1-sxwjean@xxxxxx --- kernel/locking/lockdep_proc.c | 26 ++++++++++++++------------ 1 file changed, 14 insertions(+), 12 deletions(-) diff --git a/kernel/locking/lockdep_proc.c b/kernel/locking/lockdep_proc.c index 8069783..b8d9a05 100644 --- a/kernel/locking/lockdep_proc.c +++ b/kernel/locking/lockdep_proc.c @@ -70,26 +70,28 @@ 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"); } - seq_puts(m, "\n"); return 0; }
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