linux-kernel - Re: [PATCH] locking/lockdep: Remove unused variable in __lockdep

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Message-ID: <CA+tQmHC73zSUfm1yRypjxXxpbZAoP8Bam0C__hF9Kts1XFh7GA@mail.gmail.com>
Date:   Mon, 31 Oct 2022 13:55:20 +0800
From:   chi wu <wuchi.zero@...il.com>
To:     Waiman Long <longman@...hat.com>
Cc:     peterz@...radead.org, mingo@...hat.com, will@...nel.org,
        boqun.feng@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] locking/lockdep: Remove unused variable in __lockdep_count*()

Waiman Long <longman@...hat.com> 于2022年10月30日周日 23:21写道：
>
> There is no target_entry NULL check in __bfs(), so target_entry is
> always expected to point to a valid memory location. You will need to
> add the NULL check if you want to remove it from these two functions.
>
Yes,  add code in __bfs() as follow?

if (match(lock, data)) {
    if (target_entry)
        *target_entry = lock;
     return BFS_RMATCH;
}

> BTW, have you actually exercised the code to make sure that there was no
> unexpected side effect from this change?
Yes, the code "check_irq_usage -> __bfs_backwards" is an example and the
primary callers lockdep_stats_show and l_show in lockdep_proc.c work well.

But I'm not sure I missed anything.
>
> Cheers,
> Longman
>
Thank you for reply