linux-kernel - Re: [PATCH] sched: Assert for_each

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Message-ID: <20230821175554.GA595469@google.com>
Date:   Mon, 21 Aug 2023 17:55:54 +0000
From:   Joel Fernandes <joel@...lfernandes.org>
To:     "Matthew Wilcox (Oracle)" <willy@...radead.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org,
        Tong Tiangen <tongtiangen@...wei.com>, rcu@...r.kernel.org
Subject: Re: [PATCH] sched: Assert for_each_thread() is properly locked

On Mon, Aug 21, 2023 at 02:44:28PM +0100, Matthew Wilcox (Oracle) wrote:
> list_for_each_entry_rcu() takes an optional fourth argument which
> allows RCU to assert that the correct lock is held.  Several callers
> of for_each_thread() rely on their caller to be holding the appropriate
> lock, so this is a useful assertion to include.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>

Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>

thanks,

 - Joel


> ---
>  include/linux/sched/signal.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
> index 669e8cff40c7..f1eae7f53be9 100644
> --- a/include/linux/sched/signal.h
> +++ b/include/linux/sched/signal.h
> @@ -659,7 +659,8 @@ extern bool current_is_single_threaded(void);
>  	while ((t = next_thread(t)) != g)
>  
>  #define __for_each_thread(signal, t)	\
> -	list_for_each_entry_rcu(t, &(signal)->thread_head, thread_node)
> +	list_for_each_entry_rcu(t, &(signal)->thread_head, thread_node, \
> +		lockdep_is_held(&tasklist_lock))
>  
>  #define for_each_thread(p, t)		\
>  	__for_each_thread((p)->signal, t)
> -- 
> 2.40.1
>