lkml.org 
[lkml]   [2021]   [Jun]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 3/3] locking/lockdep: print possible warning after counting deps
Hi,

On Thu, Jun 17, 2021 at 10:28:28PM +0800, Xiongwei Song wrote:
> From: Xiongwei Song <sxwjean@gmail.com>
>
> The graph walk might hit error when counting dependencies. Once the
> return value is negative, print a warning to reminder users.
>

Thanks for the improvement, but please see below:

> Suggested-by: Waiman Long <longman@redhat.com>
> Signed-off-by: Xiongwei Song <sxwjean@gmail.com>
> ---
> kernel/locking/lockdep.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index cb94097014d8..cfe0f4374594 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -2028,8 +2028,12 @@ static unsigned long __lockdep_count_forward_deps(struct lock_list *this)
> {
> unsigned long count = 0;
> struct lock_list *target_entry;
> + enum bfs_result ret;
> +
> + ret = __bfs_forwards(this, (void *)&count, noop_count, NULL, &target_entry);
>
> - __bfs_forwards(this, (void *)&count, noop_count, NULL, &target_entry);
> + if (bfs_error(ret))
> + print_bfs_bug(ret);

Here print_bfs_bug() will eventually call debug_locks_off_graph_unlock()
to release the graph lock, and the caller (lockdep_count_fowards_deps())
will also call graph_unlock() afterwards, and that means we unlock
*twice* if a BFS error happens... although in that case, lockdep should
stop working so messing up with the graph lock may not hurt anything,
but still, I don't think we want to do that.

So probably you can open-code __lockdep_count_forward_deps() into
lockdep_count_forwards_deps(), and call print_bfs_bug() or
graph_unlock() accordingly. The body of __lockdep_count_forward_deps()
is really small, so I think it's OK to open-code it into its caller.

Regards,
Boqun

>
> return count;
> }
> @@ -2053,8 +2057,12 @@ static unsigned long __lockdep_count_backward_deps(struct lock_list *this)
> {
> unsigned long count = 0;
> struct lock_list *target_entry;
> + enum bfs_result ret;
> +
> + ret = __bfs_backwards(this, (void *)&count, noop_count, NULL, &target_entry);
>
> - __bfs_backwards(this, (void *)&count, noop_count, NULL, &target_entry);
> + if (bfs_error(ret))
> + print_bfs_bug(ret);
>
> return count;
> }
> --
> 2.30.2
>

\
 
 \ /
  Last update: 2021-06-17 17:14    [W:0.060 / U:0.244 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site