linux-kernel - Re: [RESEND PATCH 1/3] completion: Add support for initializing completion with lockdep

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Date:   Thu, 19 Oct 2017 23:24:00 +0000
From:   Bart Van Assche <Bart.VanAssche@....com>
To:     "mingo@...nel.org" <mingo@...nel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "byungchul.park@....com" <byungchul.park@....com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "amir73il@...il.com" <amir73il@...il.com>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "hch@...radead.org" <hch@...radead.org>,
        "linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "oleg@...hat.com" <oleg@...hat.com>,
        "darrick.wong@...cle.com" <darrick.wong@...cle.com>,
        "johannes.berg@...el.com" <johannes.berg@...el.com>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "idryomov@...il.com" <idryomov@...il.com>,
        "tj@...nel.org" <tj@...nel.org>,
        "kernel-team@....com" <kernel-team@....com>,
        "david@...morbit.com" <david@...morbit.com>
Subject: Re: [RESEND PATCH 1/3] completion: Add support for initializing
 completion with lockdep_map

On Wed, 2017-10-18 at 18:38 +0900, Byungchul Park wrote:
> Sometimes, we want to initialize completions with sparate lockdep maps
> to assign lock classes under control. For example, the workqueue code
> manages lockdep maps, as it can classify lockdep maps properly.
> Provided a function for that purpose.
> 
> Signed-off-by: Byungchul Park <byungchul.park@....com>
> ---
>  include/linux/completion.h | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/include/linux/completion.h b/include/linux/completion.h
> index cae5400..182d56e 100644
> --- a/include/linux/completion.h
> +++ b/include/linux/completion.h
> @@ -49,6 +49,13 @@ static inline void complete_release_commit(struct completion *x)
>  	lock_commit_crosslock((struct lockdep_map *)&x->map);
>  }
>  
> +#define init_completion_with_map(x, m)					\
> +do {									\
> +	lockdep_init_map_crosslock((struct lockdep_map *)&(x)->map,	\
> +			(m)->name, (m)->key, 0);				\
> +	__init_completion(x);						\
> +} while (0)

Are there any completion objects for which the cross-release checking is
useful? Are there any wait_for_completion() callers that hold a mutex or
other locking object?

Thanks,

Bart.