linux-kernel - Re: [PATCH v4 15/15] lockdep: Crossrelease feature documentation

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Message-ID: <20170118064230.GF15084@tardis.cn.ibm.com>
Date:   Wed, 18 Jan 2017 14:42:30 +0800
From:   Boqun Feng <boqun.feng@...il.com>
To:     Byungchul Park <byungchul.park@....com>
Cc:     peterz@...radead.org, mingo@...nel.org, tglx@...utronix.de,
        walken@...gle.com, kirill@...temov.name,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        iamjoonsoo.kim@....com, akpm@...ux-foundation.org,
        npiggin@...il.com
Subject: Re: [PATCH v4 15/15] lockdep: Crossrelease feature documentation

On Fri, Dec 09, 2016 at 02:12:11PM +0900, Byungchul Park wrote:
[...]
> +Example 1:
> +
> +   CONTEXT X		   CONTEXT Y
> +   ---------		   ---------
> +   mutext_lock A
> +			   lock_page B
> +   lock_page B
> +			   mutext_lock A /* DEADLOCK */

s/mutext_lock/mutex_lock

> +   unlock_page B
> +			   mutext_unlock A
> +   mutex_unlock A
> +			   unlock_page B
> +
> +   where A is a lock class and B is a page lock.
> +
> +No, we cannot.
> +
> +Example 2:
> +
> +   CONTEXT X	   CONTEXT Y	   CONTEXT Z
> +   ---------	   ---------	   ----------
> +		   mutex_lock A
> +   lock_page B
> +		   lock_page B
> +				   mutext_lock A /* DEADLOCK */
> +				   mutext_unlock A

Ditto.

> +				   unlock_page B held by X
> +		   unlock_page B
> +		   mutex_unlock A
> +
> +   where A is a lock class and B is a page lock.
> +
> +No, we cannot.
> +
> +Example 3:
> +
> +   CONTEXT X		   CONTEXT Y
> +   ---------		   ---------
> +			   mutex_lock A
> +   mutex_lock A
> +   mutex_unlock A
> +			   wait_for_complete B /* DEADLOCK */

I think this part better be:

   CONTEXT X		   CONTEXT Y
   ---------		   ---------
   			   mutex_lock A
   mutex_lock A
   			   wait_for_complete B /* DEADLOCK */
   mutex_unlock A

, right? Because Y triggers DEADLOCK before X could run mutex_unlock().

Regards,
Boqun

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